Document N2JqQzmrOZ5eY07VpbXbNORRR

STATE OF MONTANA BUREAU OF MINES AND GEOLOGT Francis A. Thomson, Director a^ioi Memoir No. 27 T A LC, GRAPHITE VERMICUL. ITE A N D ASBESTOS DEPOSITS IN MONTANA By Eugene S. Perry MONTANA SCHOOL OF MINES BUTTE, MONTANA 19lt8 FOREWORD Illustrative of the development of the non-metallic mineral resour ces of Montana are the talc and graphite mines southeast of Dillon, the talc mines south of Snnis, and the vermiculite nine northeast of Libby. The success of these operations, and the production of other ncn-metallic minerals in Montana such as gypsum, points to an ever increasing de velopment of this phase of the mineral industry in the state which in the past has yielded in the neighborhood of $100,COO,000. Talc and the other minerals described under this cover are not di rectly related to one another, however this report is the beginning of a series in which it is intended all known non-metallic mineral resour ces of Montana will be described, Kyanite and sillimanite are described in Miscellaneous Contributions No. 10, Other ncnmetallic resources are phosphate,bentonite, gem stones, and optical calcite; and of course the production of lime, cement, and stone is the basis of important indus try. Montana is noted for its large production of metals such as gold, silver, lead, zinc, manganese, and in particular copper. Mining of these resources has been continuous for over 80 years, and has yielded a return of over four billion dollars. The lure of metal mining has over-shadowed the mining of these less glamorous materials, notwith standing their vital importance to industry in general. It is hoped that the publication of information pertaining to the non-metallic mineral resources will aid in their development. Francis A. Thomson Director iii CONTORTS Page Part I. Talc . . . ........................ 1 General considerations..............................................................................................1 General geology ....................... ... .................................. ... .................................. 2 Tala-deposits east of Dillon. ..........................................................................3 Location and topography.................................................................................. 3 Geology. .................................................. Li Axes Creek deposit ............................... ... ..................................................L Carter Creek deposit .......................................................................... 6 Timber Gulch deposit ............................... ... ................................... 6 Talc deposits south of Ennis................... 7 Geology. .......................................... Johnny Gulch deposit .......................................... 7 6 Other talc deposits in the Cherry Creek series. ....................................... 10 Talc deposit south of Helena..................................................................... ...10 Geology................................ .......................... ...................................... ..10 Pyrcphyllite near Argenta ..... ................................................... ...11 Part II. Graphite...................................... .... ..................................................13 General considerations.........................................13 Crystal graphite mine ......................................................... 13 Occurrence and origin of graphite. .. ................ ........15 Mining and treatment .............................. 16 Graphite mine on the Bird's Nest claim, .......... ................ 17 Graphite in the Timber Gulch talc deposit ........ .................... 18 Graphite -west of Dell .................................. 18 Scattered occurrences of graphite ..... .................... .......20 Part 111. Vermiculite. .....23 General considerations. ....23 Vermiculite deposits near Libby .......................................... 2h Geology. ....... 26 Vermiculite deposits near Hamilton. ... ............................... ,. ...25 Vermiculite deposits in the Bearpaw Mountains near Boxelder ................ 30 Vermiculite deposits near Pony. ...................................................................... 32 Lica-bearing dike south of Bozeman. ................................................................. 3U Part IV. Asbestos .......................................................... ....35 General considerations. ...................................... 35 Asbestos deposits near Karst. ... ............................................................... 36 Location and accessibility ...................................................................... 36 General geology................*............................................................................37 Development. ..... .............................................................................. 38 Mining and milling..................................................................... .... 38 Serpentine asbestos near Cliff Lake ............................................................... 39 Location and development.................................................. 39 Geology. ...................................................... UO Asbestos near Libby .......................................................................... .....LO Cther occurrences of asbestos.............................................................................kl Bibliography. ....... ...................................................................... ..U3 -v- ILLUSTRATIONS Page Plate 1. A, View of Smith-Dillon talc mine. B, View of Crystal graphite mine. C, View of Johnny Gulch talc deposits. D, View of Karst asbestos pit. E, View of Libby vermiculite deposit. ..... ............................... ... Frontispiece 2. A, Geologic sketch map of the area between Dillon and Ennis. B, Geologic sketch map showing talc and graphite deposits in the Dillon area.............................................................. 2 3. Map of the Smith-Dillon talc mine southeast of Dillon .... L ' h. Map of Johnny Gulch talc deposits, Madison County ..................... 5 5. Lap of Crystal graphite mine, Beaverhead County ........................ 1U 6. A, Map of lower Birds Nest workings, B, Map of Dubie level. Crystal Graphite mine..........................................................................16 7. Photographs of specimens of nonmetallic minerals............................ 20 Figure 1. Map of Carter Creek talc mine, Beaverhead County. .................... 5 2. Map showing location of talc deposit near Helena......................... 12 3. Map showing location of graphite deposits west of Dell. ... 19 h. Geologic map of Libby vermiculite deposit, Lincoln County . . 26 5. Map showing location of vermiculite deposits near Hamilton. . 29 6. Map showing location of the vermiculite deposits in the Bearpaw Mountains in'Hill County. ................................................... 31 7. Map showing location of vermiculite deposits near Pony. ... 33 8. Map showing location of Mica Creek deposit and the Karst asbestos deposit in Gallatin County ............................................... 36 9. Map showing location of CJli'ff Lake asbestos deposit, Madison County..........................: i : ; ; :......................................................39 - vi '* VEKMICULITE AND AS-BESTO ^ .4SE?^ DEPOSITS I N MONTANA By ' Eugene S. Perry PART I. TALC General considerations - The mining of talc has been carried on in Montana for about six years, and this mineral is now being produced in commercial quantities 11 miles southeast of Dillon and 20 miles south of Ennis, Deposits are known-at several other localities in southwestern Montana, and some of them may be workable. Talc is a hydrous silicate of magnesium.: It is characterized by its ex treme softness and its soapy feel. In color it is light-gray to white, and some varities have a greenish tinge. In texture it is commonly too fine grained for individual particles to be easily observed and it may resemble soap, but it may also be micaceous or foliated with flakes or fibers visible* to the unaided eye. The natoe steatite may be applied to the pure compact mierocrystalline types. Soapstone is a rock containing 50 to 75 percent of the mineral talc together with rock impurities, and it is not known to occur in commercial deposits in Montana. To be of conmercial grade soapstone should be of such a character that it can be cut or sawed into thin slabs such as are used for table tops in chemical laboratories or in electrical switch boards, and the slabs or panels should be free of incipient fractures, cracks, or breaking planes. Serpentine, which resembles talc, and which also occurs south east of Dillon, is considerably harder than talc. The conmercial value of talc lies in its soft character, its chemical in ertness, its ability to be finely pulverized with ease, and its ability to nd* readily with other ingredients when finely powdered. Also it has"He ability to be "burned" or baked, with or without binder, and with low shrinkage. It forms a porcelain-like product, with low heat and electrical conductivity. In burning a chemical change takes place. Deposits of common talc are relatively plentiful in the United States and foreign countries, and supply exceeds demand; hence competition within the in dustry is keen and prices are held to a relatively low margin of profit. The largest volume is used in ceramic products. Exceptionally high grade of pure talc is used in manufacture of cosmetics, and special varieties (such as "lava" talc) are uMd in making radio-tube insulators; such varieties bring premium prices. Cost of transportation is an important item in the sale of the ceramic grades of talc, and Montana is a long distance from markets. United States production of talc and soapstone in 1937, an average pre-war year, was 230,000 tons valued at $2,562,000, or slightly over $11 per ton. About 90 percent of the talc marketed in United States is pulverized before sale. It is used in the manufacture of certain paints (U8$), paper (16$), roofing materials (11$), rubber (11$), toilet powders (3$), foundary facings, ceramic products, and many other products. Only the finest and purest grades are used in toilet powders, lotions, and face cream. An unusual variety, -1 - knoim consnercially as "lava" talc, can be machined into intricate shapes in crude form, burned into a finished product resembling porcelain without change in shape or Bize, and in this form it is used as an insulator and spacer in vacuum tubes and electrical instruments. It is said that there is no satisfactory substitute, and also that the Montana material is superior to imported material which has supplied most of the market. Ceramic (common), cosmetic, and lava talc all have been mined and marketed from Montana. General Geologr Geologically, in Montana talc is known to occur only in rocks of two geo logic ages. A small vein-like deposit about one mile south of Helena was de veloped in dolomite of the Pilgrim formation of Cambrian age. This deposit has been practically worked out, but it is of raich geologic significance. The larg est deposits occur in dolomitic marbles in the Cherry Creek series of early preCambrian age in a region 1x0 miles across extending from Madison River valley near Ennis to Blacktail Deer Creek valley near Dillon. (See Plate 2, A), The two commercial mines now operating on Axes Creek southeast of Dillon and on Johnny Gulch south of Ennis are in this area. Other deposits in this area are on Timber Gulch and Carter Creek near Dillon and Granite Creek and Idaho Creek near Virginia City. Minor occurrences of talc have been observed in several other localities, and in a few places opened by pits. It may be exptected that minor amounts of talc may be found in the marbles of the Cherry Creek series almost anywhere in this area, although it is not .likely that large commercial bodies are present and have been overlooked. The Cherry Creek series, named by Peale in 1896 from a creek by that name 20 miles south of Bnnis, is a most intensely metamorphosed series of early preCaabrian schists, phyllites, light- and dark-colored gneisses, amphibolites, schistose quartzites, and coarsely crystalline marbles, locally containing gar net^, staurolite, kyanite, sillimanite, and similar minerals. The thickness has not^seen measured accurately, but it probably is in the order of four to six thousand feet. Individual beds of characteristic rock types from a few inches to several feet in thickness may be distinct and well defined, and the thicker units may be traced in outcrop for several miles. The series is-definitely of sedimentary origin, but it has been intruded by dikes and sills some of which are metamorphosed. Both major and minor folding are prevalent, and in some places folding is isoclinal or overturned. Crumpling of beds is common. Of particular interest in talc prospecting are the zones of marble in the series. As observed on Axes Creek, at least six marble members are present, and some are U00 to 800 feet or more in thickness. The amount of marble to be obser ved in the series decreases eastward, and members of the series cannot readily be correlated between Dillon and Ennis. Because of the abundance of the marble in the series on Axes Creek it is suggested that the rocks in this area be called the Axes Creek phase of the Cherry Credc series, and that the name Cherry Creek be retained for these rocks over the entire region. A detailed study of this series of rocks is being made by E. YT. Heinrich for Montana Bureau of Mines and Geology during 19U8, This complex series of rocks, known to be present in a region 75 miles or more across underlies folded Cambrian strata. The Belt series of late preCambrian age is absent in this part of Montana, but as determined fc^jiegree of metamorphism, it is very much younger than the Cherry Creek serior^g^Xhe base of the Cherry Creek is in question. Commonly at the base is a highlj&fitotaaorphosed series of feldspar gneisses in which crumpled bands are conspicuous*-.- This gneiss taari^s could be metamcrpfyosed sediments older than Cherry Creek, but sere likely -2- 1% is mtaaorphoawd boss of igneous rook such as gvanite which was intruded v into the Cherry Creek prior to its intense regional aetanorphisa. The tens . Pony series is commonly applied to the gneiss series*. Talc is believed to have originated by the action of hydrothermal (bet water) soluhjgjjns acting upon magnesium-bearing rocks through which the solu tions passedg^he process having occurred when the rocks were deeply buried* Talc is not ttjiieved to form by action of the surface waters. Elsewhere than Montana talc occurs in dark-colored igneous rocks and gneiss as well as in crystalline dolonitic marble, but no occurrences of importance other than in marble are known in Montana. The Dillon, Ennis, and intervening talc deposits are all similar in gen eral occurrence. Small vein-like bodies one-quarter inch to 2 or 3 inches thick locally appear in the marble, extend 1 to 5 feet and then cease. Large bodies, which may be in the order of 50 feet wide and 300 feet long, are irreg ular in shape and cease to be vein-like. Most of the bodies lie parallel to the original bedding, traces of which show in the marble, but they may also cue across bedding planes. In large talc bodies, blocks or cores of unaltered marble may lie within and be entirely surrounded by talc. Practically all con tacts between talc and marble are sharp. Disseminations, noticeable in hand speciman, of talc in marble or marble in talc are seldom observed, although microscopic studies show talc disseminated in marble. Impurities, essentially unaltered rock, may be present in the talc locally. Some deposits are unusual in that crystalline graphite in parallel flakes as much as one-eighth inch across are thickly dispersed through the talc, th* alinement being parallel to that of the talc body and the bedding of the marble. Other deposits appear to have contained pyrite, the evidence of whiqb now consists of limonite (iron oxide) scattered through the talc in small .lu*8 or pseudomorphous crystals after pyrite. Silicate minerals such as tremolxte are so rare as not to be commonly observed with the unaided eye. Graphite, limonite, or rock impurities in some Montana talc makes it unsatisfactory for industrial use, however many large bodies of talc are completely free of these impurities. Talc Deposits East of Dillon Location and topographyt The largest production of talc in Montana comes from a deposit on Axes Creek, 11 miles southeast by road from Dillon, the nearest shipping point. A large body of massive talc near creek level has been opened by the Tri-State Minerals Company of Los Angeles by means of an open cut, adits, a winze, and drifts at a lower level* During 19U6 approximately 5,000 tons of broken but uncrushed talc were marketed. This company also has opened deposits on Carter Creek seven miles northeast, and on Timber Creek two and one-half miles southwest from the Axes Creek deposit, and has investigated other deposits1 in southwestern Montana. Commercial shipments have been made only from the Axes Creek deposit by this company. (See plate 2, B.) Dillon,, population about 3000, is the county seat of Beaverhead County and the largest city in this part of Montana. Farming and stock raising are the principal industries, but considerable metal mining is also carried on in the vicinity. The city is serviced by a branch line of the Onion Pacifie Rail way extending from Salt Lake City to Butte, and an oiled highway, U. S. 91* Fair to good roads radiate into the surrounding mountains and valleys. The altitude of Dillon is 5090 feet above sea level. The topography, of this region is characteristic, of that of western Montana wherein high rugged mountain ranges trending north to south are separated by broad relatively level valleys containing hundreds of feet of lake and alluvial -3- deposits. The mountains rise abruptly froms such valleys with steep slopes dis sected by gullies or gulches, but commonly the mountains flatten on top to broad rolling uplands, remnants of an ancient erosion surface developed in early Tertiary time. Timbered areas are local, and vegetation on most of the area is grass and sage brush. The Dillon talc deposits are on the lower slopes of such a range known as the Ruby Mountains. Several roads easily traveled in dry weather cross this range or lead to its summit. Geology The Cherry Creek series, the marbles of which contain the talc deposits, is excellently exposed on the west or northwest slope of the Ruby range southeast and east of Dillon. The more resistant ledges crop out in bold relief from the margin of the Tertiary lake and alluvial deposits in the major valleys upward to the top of the range at altitudes from 5500 to 8500 feet above sea level.- The bedding has a general northeasterly strike, and dips are northwestward from 30 to 70 degrees; however, minor folding and crumpling of strata produces notable local variations. Probably nuch faulting is present, but faults are not easily recognized due to similarity cf rocks and complex folding. Most conspic uous rock types usually observed are marble and gneiss, although schist and quartzite are present. Crystals of garnet and masses of sillimanite and simi lar minerals occur locally in the schist and gneiss, but in general garnet is not particularly plentiful. Serpentine occurs in the marble members, but it is not closely associated with the talc deposits. About two miles south of the Axes Creek talc deposit, high on the mountain, are commercial concentrations of crystalline graphite (described in Part II of this report). Igneous activity shows itself in most of the mountain area in the form of numerous pegmatite-dikes which irregularly cut the metamorphic rocks. More than one age of pegmatite is thought to be presenti An old type is much metamorphosed; the younger and most conspicuous type, composed essentially of feldspar, quartz, and nuscovite, shows no sign of deformation since its intru sion, Pegmatite is not notably associated with the'talc, as it is with the 'graphite. Metalliferous mineralization, although present in the mountains, is insignificant. The nearest known mass of granitic intrusive rock is 25 miles northwestward, however seven miles southeast of the Axes Creek deposit is a series of ultra-basic intrusives, and late basic dikes are plentiful in the area. The marbles on Axes Creek can not be definitely correlated with similar marbles in the Cherry Creek series south of Ennis, but they are considered to belong to the same series of rocks. In general the marble is a pure coarselycrystalline carbonate rock in which individual grains up to one-eighth inch in diameter are interlocked together. Leached with acid it may show 10 percent or more of insoluble material consisting of quartz and silicate minerals including talc. In talc-bearing areas marble may contain much disseminated talc not readily visible. Near the top or bottom of a marble member a few feet of schist may separate a few feet of marble from the. main mass. Remnants of original bed ding are common, and in places close crumpling within the marble mass has been developed. No structural or stratigraphic control of tala occurrences within the marble was observed, the talc appearing and disappearing abruptly. Axes Creek Deposit; The Axes Creek deposit, as exposed in workings, is abcut UOO feet long, 60 to 100 feet wide, aid more than 200 feet in vertical extent. It is known by the operators as the Smith-Dillon talc mine. (See plate 3). Although the deposit is irregular in shape, it is elongafcaiteroughly parallel to the strike of the marble, - Vertically, the deposit stani^jvt a stnep angle, but the bedding of the marble dips about 7Q degrees nositfeest. Faulting Is present as indicated by thick clay gouges and crushed zones, and it - u- 'MONTANA BUREAU OT MINES AND GEOLOGY MEMOIR NO. XI. PLATE S is possible talQ.hae deve^epmd ia .tke msrtls *djMnt to trlorm*.v. : \ strike fault*. gamwvar, j&ickensided faniy^l^nf end lpeeela-ac^Mejfsf. :::.; through the tela indicating movement since tale fegpatlciv* 2|C^thi- tl|e Jbedj :of talc are "ribs" of marble, some of which may ) 3Ct-/et or mo^awidf* *"lt jniT talc mary across is present without evidence pf pre-existing aprULe ia the talc sSBEtture. T^e talc lies at the southeastern stdr aT7E~B&iXfnKifeer which exteSpcontinuopsly 800 feet westward before becoming buried -beneath .the valley-filT^jf Beaverhea^ Valley. Small stringers and irregular bodies of tele were not observed in the .marble in the area adjacent to the deposit, and in this respect the Axes Creek deposit differs soqpshat from others. Intensely metamorphosed beds of quartzite, somewhat resembling vein quarts, overlie-the i marble at the Axes Creek deposit. Schist Marble To Eilloa\^ *. V Marble <; \ <*-TaIc'- Iff] Talc ! Dolerite dikes Figure I. --?.jap cf Keystone talc deposit on Carter Creek, Beaverhead County, Development work, some, of which is shown on the accompanying map, (Plate 3 ) consists of about 1500 feet of adits and drifts on a main haulage level 30 feet above the creek, about U00 feet of drifts on a level 60 feet lower than the main level by way of a winze, and an open cut approximately 1*00 feet long and 100 feet wide on a hill side 50 to 150 feet above the adit level. The talc supports itself well in underground workings and very little timbering is needed in exploratory work. Development work has been carried on almost en tirely in talc, most of the material mined being suitable for shipment. In the open cut, talc is drawn by drag-line scraper to a shaft and dropped to the haulage level from v;hich it is trammed to bins on the surface. The run-of-mine - $- material ia not crushed or milled,- although hand-sorting is practiced to remove "blocks of limestone or impure material. The talc is washed to remove clay im purities "before being hauled by trucks to Dillon, from which point it is shipped o Ogden, Utah, for further treatment before being marketed. Carter Creek Deposit* The deposit on Carter Creek, known by the operators as the ffeystone mine, is eight miles northeast of the Axes Creek deposit, and 13 miles east of Dillon by roads easily traveled in dry weather. (See plate 2 ). It is low in the foothills of the range, and lies in one of the marble members of the Cherry Creek series as does the Axes Creek deposit. Metamorphosed quart zite is not associated with the marble as it is on Axes Creek. Exposures of the -irregularly-shaped deposit of talc are in an area about li50 feet long and about 100 feet wide; and a shaft 60 feet deep, together with over 300 feet of drifts at its bottom are all in talc (fig. 1). Several small separate bodies of talc lie to the northeast and southwest within 500 feet, and veinlets and ir regular masses a few inches thick and a foot or two long are scattered through much of the marble member which appears to be about 600 feet thick. The irreg ular deposit, although in part parallel to bedding in the marble, also cuts across bedding locally, and it appears to have a northwesterly plunge across bedding and beneath surface exposures of marble. The marble dips about 50 N7f. Dolorite dikes perhaps 25 to 50 feet thick cut the marble in this locality. The talc, which is light-gray, dense, and fine-grained, is of good quality, bu-t contains many small lumps of limonite (iron oxide) apparently altered from pyrite scattered through the bocfcr. Some graphite occurs sparingly in the talc. The presence of limonite, which cannot be separated in mining, yields a color to the pulverized product causing.it to be less satisfactory for uses where a pure white talc is desired, and tije deposit'has not been worked for the market. The deposit is, however, a large potential reserve of commercial talc suitable for many uses. % Timber Gulch Deposit* The Timber Gulch deposit, known by the operators as Crescent mine, is three mile s' Axes Creek deposit. (See plate It is accessible by automobile rgj a dirt,road which branches off the road to the Axes Greek deposit and follows southward along the main valley. It lies near the margin of the valley-fill of Blacktail Deer Creek at the foot of the mountain!fcslope. Two neuters of impure marble, 10 to 15 thick and separated by about 150 feet of micaceous gneiss, have locally been repAced entirely or in part by talc. Intermittent exposures of talc may be followed for 800 to 1,000 feet along the strike of the marble, which dips northwesterly at about 50 degrees. A shallow inclined shaft and pits expose the talc to a dqjth of 10 to 20 feet. The marble is much decomposed locally, and may appear as a brownish friable rock which can be crumbled in the hand. Passive pegmatite dike? occur close by. The deposit is unusual in that disseminated through the talc are thin flakes of crystalline graphite up to one-eighth inch across, the quantity of graphite in places amounting to perhaps one-half of one percent. The flakes lie parallel to one aa other, and to the bedding of the marble, and the individual flakes are distinctly separated from each other. Flakes of graphite and grains of talc and other silicate minerals are disseminated in the marble. The talc itself is gray and fine-grained, and of a coimnercial quality, but the presence of graphite in the talc has caused the abandonment of the deposit, at least for the present time. . - 6- ' TAW BEPOSITS 90UTB*O? HHHS - Th talc deposits 20 miles south of Ennis lie about U silewfrom state Highway 1*^191, up Johnny Gulch in the low foothills on the east side of, the GravellyqpSige. (See plate 2j A). Ennis is a small town witb^population of about hoyiut the nearest shipping point is Norris, popwiatim-about 75, which is*5fe~-the end of a branch line of the Northern Pacific Railway about 35 miles north of Johnny Gulch. State Highway 191, which passes through Norris and near Johnny Gulch, is a modern oil-surfaced road, readily traveled through* out the year. The road from the highway up Johnny Gulch to the talc deposits crosses Madison River on a steel bridge known as UeAtee Bridge, and although essentially a dirt road may be traveled most of the year. Stock raising and some metal mining are the chief industries in this region. The altitude of Madison River valley is about $000 feet, and of the sumnit road along Gravelly Range, 9000 to 9500 feet. Altitude of the talc deposit is between 5500 and 6000 feet. Geology; The Gravelly Range is made up mainly of Paleozoic and Mesozoic strata bent into broad open folds by Laramide (Rocky Mountain) orogeny or mountain making. The pre-Cambrian metamorphic complex is exposed low in the foothills on the east aide by erosion of overlying Cambrian strata. Along Madison River valley the metamorphic rocks are buried baneath alluvial and lake deposits. The uppermost pre-Cambrian Belt series, so widespread in north western Montana, is absent in this region. The metamorphic rocks, named the Cherry Creek series after the first*creek north of Johnny Gulch, are somewhat different from those on Axes Creek, not only in lithologic character, but also in the sequence of the various meafcers. They consist of light- and dark-gray gneisses, mica schists and phyllites, schistose quartzites, and dolomitic marbles, and excellent exposures of the series show in bands which have a general northeasterly strike. Although as previously stated the series is of sedimentary origin, metamorphism has pro ceeded so far that all original sedimentary minerals are changed to metaaorphio minerals, and sedimentary structures such as ripple marks have completely dis appeared. Crystals (metacrysts) of garnet, staurolite, kyanite, and similar minerals are plentiful in the gneiss and schist, and in places may constitute one-fourth of the rock. Deposits of kyanite (aluminum silicate) associated wL th pegmatite in the gneissic area six miles north of Johnny Gulch are poten tially commercial. Ihe beds of the Cherry Creek series have been closely com pressed by folding; dips are commonly more than 60 degrees, and in mary places bedding stands nearly vertical. An area of gray gneiss south of Ruby Creek probably corresponds to the Pony series. Marble appears in several bands striking across the area, but there may be repetition by folding. The largest area of marble, and the area in which the comraeroial deposits of talc lie, is between Johnny Gulch and Cherry Creek; it is about 5' miles long in the direction of the strike of beds and l miles wide. The. rock weathers to dirty brown granular surfaces which look dark in the distawe. Due to its resistance to weathering it forms a conspicuous' ridge known locally as Black Point, extending perhaps half a mile into Madison Valliy. For this reason the marble has been called the Black Point dolomite, however the writer feels it is better not to name members in the Cherry Creek series permanently until the sequence, thickness, and character of the various units are determined. Bedding in the marble at Black Point stands nearly ver tical, and the writer is of the opinion that the one and one-hald mile width of the area results from repetition of beds cither by faulting or folding. Talc in minor quantity has been observed in the areas of marble other than Johnny Gulch, and one deposit about 1^ miles north of Morgan Gulch was opened by a shallow shaft and pits sunk by the Tri-State Minerals Company. It was abandoned because of low grade and lack of quantity. Small local deposits of manganese cocide, worked during World War I, are present in several of the marble areas. On Cherry Creek such a deposit contained much hematite (iron ox ide). These minerals are apparently superficial. Metalliferous mineralization is present as veins in the gneisses and schists, but no commercial mines have as yet been developed. Evidence of igneous activity, other than pegmatite dikes and late lava flows, has not been observed in the area. Probably dikes or sills are present, but the nearest observed large mass of intrusive igneous rock is the Tobacco Root batholith about 25 miles north of Johnny Gulch near Norris. Basalt flows cap parts of the crest of the Gravelly Range, and small'patches of rhyclitic lava rest on the metamorphic complex in several places. Some of the rhyolite is within the talc-bearing area. Johnny Gulch Deposits; The talc deposits on Johnry Gulch (See plate U) occur'as isolated bodies in relatively pure marble over an area at least 2000 feet 'i.o:sg and 800 feet wide, and talc may lie beneath a soil covered area im mediately west. Showings of talc also occur 1^ to 2 miles west of the deposits now being worked. In the area being mined, five or six bodies opened by cuts arid adits are 100 to 150 feet long and 25 to 50 feet wide, and many smaller bodies are present. Almost innumerable small masses or veinlets of talc appear and disappear abruptly in the marble of the talc-bearing area. All the bodies Lend to be elongated in the direction of strike of bedding in the marble, but the larger bodies are irregular in shape, and in part may cut across bedding. The l.odies appear to continue vertically in depth, however bedding in the . marble dips at angles ranging from 80 to perhaps 88 degrees. Probably the de posits cease in the vertical dimension as rapidly as in the horizontal. Pits, ftrenches., shafts, adits, and underground workings, numbered up to 18, have been sunk iato the larger deposits, and many unnumbered pits have been dug. In places jthe thin soil covering has been removed by bull-dozer cuts. Tbe talc differs somewhat in appearance from place to place, and different grades are classed as ceramic, cosmetic, and lava. The difference between cer amic and cosmetic appears to be a matter of purity, or color, but lava talc apparently owes its peculiar properties to some physical condition within the talc, possibly a permeability. That type called cosmetic commonly occurs in concretion-like masses up to 6 or 8 inches in diameter with interior radiating talc structure, these concretionary masses lying vi thin a body of massive talc. Most of the talc is massive and so fine-grained as to resemble soap in appear ance, but some is granular or micaceous. That type known as lava generally has dendritic (fern-like) growths of black manganese oxide reaching into the talc from fracture planes in most intricate and pleasing patterns, but some lava talc is without dendrites. Colors of the talc range from white through light- gray to dark-gray, but conmdfily greenish or bluish tinges appear. Crushed zones within the talc are present. Some talc shows an indistinct banded struc ture in tones of gray, the darker gray resulting from microscopic black specks, possibly iron oxide or carbon. In some places this banding is crumpled similar to drag folds, a condition which the writer believes is residual from pre existing marble which has been replaced by talc. (See plate The lava grade talc, which occurs mainly in pit no. 9 but also in.'^jjier places nearby and on the Queen Claim 1^ miles westward, is associateifStth much powdery and compact iron oxide and some manganese oxide in a thick of > ...soil and weathered rock. Solution cavities containing oxide material extend MC MOMTAMA BUKXAU OP MINES AND GEOLOGY MEMOIR MO. IT, PLATS MAP OF JOHNNY GULCH TALC DEPOSITS. MADISON COUNTY % downward Into the Burble. It appears that the development of this type of talc is related to intense conditions of weathering since the original talc deposition, and it is possible that the presence of the iron and manganese oxides have, acme bearing on its development. Chemical composition of lava talc frco||i$t 9, and ceramic talc from other pits is not materially different as shown .the following analysis. Pit 5 Pit 7 Pit 9 SiO^ 61.70 % 61.29 % 61.76 % Analyses of Talc ( u. S. Bur. Mines) Fe23 AI2O3 Cao MgO Na^o 1.29 % 1.36 % 1.33 % 1.55 % Tr. 1.3U %' Tr. 1.51 % Tr. 32.Ui % 0.37 % 31.26 % .26 % 31.95 % .21.% V 0.U6 > .33 .32 % J Tfalls of the larger bodies of talc are irregular and may show bowl-shaped bulges or recessions in the marble. Also "ribs" of marble may be present with in the body of talc, however, silicate minerals other than talc are seldom observed, at least with unaided eye. Coarsely crystalline calcite, both white and colored, occurs locally. Jasper (a brown fine-grained iron-bearing variety of quartz) is plentiful in irregular and vein-like masses paralleling strike of beds in the central part of the area. Although within a few feet of talc bodies, there is no apparent direct relationship. Wich jasper is also present at the southern end of the area where it appears to occur as irregular masses replacing marble. The Johnny Gulch deposits were discovered by Lewis Clark on his homestead shortly after the turn of the century, and later were opened by shallow pitst In 19U2 L. F. Teutsch obtained a lease on the property, and, operating under the name of Mountain Talc Mines, carried on exploration by digging larger pits and driving adits into exposures of talc. The "lava" grade talc was soon rec ognized by eastern consumers, and with war-time demand for this important material, development proceeded rapidly, in part by aid of-the U. S, Bureau of Mines. Commercial quantities of the lava talc were found only at the one lo cality known as Pit No. 9, and exploratory work as well as mining was concen trated on this deposit. A 2U0-foot adit, known as Madison tunnel, was driven by the Tri-State Minerals Co. into the hill slope so as to cut the deposit about 80 feet beneath the surface. Soon after a 75-foot shaft was sunk through the out-crop of talc by the U. S. Bureau of Mines, and drifts driven at its bottom. Lava talc was found at depth in narrow vein-like bodies cutting fresh marble, but it could not be mined without shattering, and hence could not be produced commercially, - Early work was concentrated on the lava grade talc, and the first ship ment of U000 pounds sent by express to the American Lava Corporation of Chatanooga, Tenn., was made in December 19U2. In the fall of 19U3 and spring of 19Uli, while exploratory work was being carried on, it is reported that 37 tons of the critical mineral was mined and shipped during the winter, and 90 tons during the following spring. Shipments have continued from time to time. Although large quantities of ceramic talc are present, only a relatively small amount of this material has been shipped, largely due to distalce from railroad and low value. The variety classed as cosmetic talc has been shipped as supply and market demand permitted. Information is not at hand to calculate total reserves, but it is believed that many thousands of tons of ceramic talc is available for mining, and much is present in mine dumps. - 9- Mining has been mainly by open cut methods, although short adits have been driven. The 3ureau of Mines 75-foot shaft and drifts were driver. Ur-;.ly for exploratory purpose, and although lava grade talc v/as present at depth, shipments of this grade came from the open cut near the collar of the shaft where larger blocks could be more readily obtained from weathered and disintegrated material, pieces weighing 5 pounds or more are desired. The blocks were trammed from the pit to a sorting floor where they were classified largely by siz'e^and freedom from cracks, then hauled by truck to Norris. The operation requires much hand labor. Cosmetic talc is obtained largely by selective mining in those portions of the deposits where this grade of talc is present. This variety is particularly plentiful in Pit 18. Ceramic talc was shipped from a lar|e open cut and adit known as Lower Pit 5* Other Talc Deposits in the Cherry Creek Series Talc has been observed in the marbles of the Cherry Creek series of this region at localities other than those already described. (See plate 2-A ) One about two miles up Granite Creek north of Virginia City occurs in a 65foot marble member which dips southeast at 60 degrees. It is opened by a short adit and shallow pits. Small stringers and repla cement bodies of talc may be observed, and hand specimens of fairly good talc maybe obtained; however, most of the talc is impure, and talc of shipping grade in quantity is not exposed. Another deposit is reported to be present southwest of Virginia City on Idaho Creek. The hand specimens of the talc are good, but as a whole the de posit is said zo be small and the average material impure. As is to be inferred from the preceding descriptions, prospecting for talc should be confined to areas of dolomite, dolomitic limestone, or dolonitic marble, in the proximity of igneous activity. Talc Deposit South of Helena The talc deposit south of HeleHia is about one-quarter mile south of the city limits at an old abandoned quarry from vhich rock was obtained for the manufacture of lime. In this early operation a mineral which would not burn to lime was recognized, but it is said that the mineral was not identified until years later. In 1935 Mr* James LcKelvey of Helena, owner, began mining the-x-deposit, and in the course of a year several hundred tons valued at 10 per ton were shipped to eastern markets. The deposit of visible talc proved small and was soon exhausted, and with no new discoveries, operations ceased. C- ,ctThe talc appears to be a replacement along a fissure cutting massive dolomite of the Pilgrim formation of Cambrian age, total thickness of the dolomite being about 600 feet. Talc may be traced intermittently for 350 feet along the surface. Irregular vein-like bodies and small stringers range in thickness fran less than one inch up to six feet. Vertically a body may ex tend 12 feet or more. Dimensions of the largest stope driven in talc ares length 35 feet, width 6 feet and height 8 feet. In this stope the taLc body dips steeply to the southeast, whereas the strata dip northeast 30 degrees. Prospecting has not been carried on to depth, and it is not definitely known if additional bodies of talc underlie the present workings. Within the talc, irregular masses of unreplaced dolomite from a fraction of an inch to a foot or more across are scattered irregularly, and-38%)ally thin streaks of chalcedonic quartz are present in the talc. The wails jjMg-'irregular and in places silicified. Although the talc-dolomite contacts may^*|pear sharp ly cut as seen in the ground, microscopic studies show gradation across 10 - such: bcnsdarlos. In limonite altered from pre-existing pyrite la . _ present in the talc* -^u: talc itself is characteristically "hit*, and most oX^it is so fine-grained that it superficially resembles soap. In places the ' . talc is coarse enough so that individual flakes up to 1/2$. inch acrosa may be . seen in rgjftating clusters or small veinlets cutting finer-grained talc. Also . the coarsS^material appears to be adjacent to the dolomite co'ntacta x Obdar . hand len^^js flakes have a pearly luster. '' The tfambrian strata in this locality are bent into large open folds, and faulting occurs locally. About one-half of a mile southward a diorite dike cuts the strata, and a short distance beyond is granitic rock of the Boulder batholith. Small intrusive stocks related to the Boulder batholith are present within one mile to the north. Age of the intrusives is late Cretaceous or early Tertiary. The sedimentary rocks throughout the area have been much al tered by igneous action, and their appearance differs from that in regions unaffected by igneous activity. No pegmatite dikes have been observed in the vicinity of the talc deposits. This part of Montana has been one of the most important gold-producing- areas in this state. Unquestionably the talc is a replacement of dolomite, and it must have been developed by hot solutions escaping from below. An analysis of the Pil grim dolomite from this locality shows U3.3 percent magnesium carbonate and 5U-6 percent calcium carbonate, and this may be the source of the magnesium in the talc. Of interest are the age relationships, wherein the talc must have been developed in Tertiary time subsequent to the intrusion of the igneous masses. By inference this may have a bearing on the age of the other talc de posits in Montana near Billon and Ennis. PYROPHYLLITE HEAR ARGENTA The talc-like mineral, pyrophyllite, has not been produced commercially in Montana, although deposits of it are known. A deposit which may be com mercial in sice and grade occurs one-half of a mile northeast of Argenta, 12 miles northwest of Billon. It lies about 300 feet north of Rattlesnake Creek and about 50 feet higher in elevation, low down on the rolling hills which rise northward from the creek. Pyrophyllite is a hydrous aluminum silicate so similar to talc that the two may not be easily distinguished, except by chemical tests. The presence of magnesium in talc and of aluminum in pyrophyllite distinguishes these two minerals. Principal uses of pyrophyllite are in the ceramics industry wherein it is used as an ingredient in manufactured products similar to those made from talc. Hence it is a competitor of talc, but it has not entered into use as exten sively, possibly because known deposits are not as plentiful or as well devel oped. North Carolina is the principal producer, although it also occurs in California. Value of crude material is not greatly different from that of ceramic talc, which in crude form ordinarily ranges from $10 to $20 per ton at the mines for good grades. The Argenta deposit of pyrophyllite occurs as nearly vertical tabular bodies cutting granitic igneous rock. The mineral has developed by alteration in place of the original rock. There are no definite walls to the altered zone. Pyrophyllite is exposed in two large pits up to 15 feet deep in the altered zone, and it also shows elsewhere in an area about 200 to U00 feet across. In general, in this locality the igneous rock is relatively unaltered. However, bands of what appeared to be nearly pure pyrophyllite 2 to U feet - 11 - . across may be seen in the face of the pits. These bands are interspaced with ds of a somewhat impure material which has a sandy appearance. A sanple of more pure part of the pyrophyllite deposit when panned yielded 10 to 15 per t of milky quartz in grains up to 1/10 inch in diameter. The pyrophyllite is extremely fine grained. Practically no iron-bearing (black) minerals are pres ent in the altered zones, but they show in unaltered rock, i The strike of the altered zones is nearly due north, but definite evidence of prominent fissure zones is obscure. The igneous body is a small local intru sion, somewhat stock-like in character, which cuts the argillites and quartzites of the Belt series of pre-Cambrian age. The age of the intrusive is no doubt late Cretaceous or early Tertiary, as are other intrusive masses in this general region. Metalliferous deposits, particularly those df gold, silver, and lead, are plentiful near Argenta where mining began in about 1865, and has been carried on intermittently since that time. The future of this pyrophyllite -`leposit would seen to depend on the initiative of local promctors, the quality of material wnich can be produced in shipping quantities, and the market demand. The presence of large commercial deposits of a good grade of talc in this part of Montana, which are being efficiently operated, detracts from the possibility of the present successful development of the pyrophyllite.. Ixplanation Dj Jefferson limestone Cdc Dry Creek shale Cpg Pilgrim dolomite -p Park shale 6m Meagher dolomite w Y/olsey shale Cf Flathead quartzite Ab Belt series qm Quartz monzonite Scale: 2 in. s 1 mi Figure 2.--Map showing location of talc deposit south of Helena - 12 - PART n. GRAPHITE General Considerations CryStjfefie graphite of a quality equal to that inpoftad into the Uhited States fhgfrlon occurs in commercial deposits southeast* of Dillon. About 2,200 tonfS^concentrates have been marketed. Dillon, with a population of about 3,000, is the county seat cf Beaverhead County. It is on a branch line of the Union Pacific Railroad, and also on U. S. Highway No. 91. It is the principal city in southwestern Montana where agriculture, cattle raising, and mining are the chief industries. Crystalline graphite, which is pure carbon, is one of the most easily identified minerals because of its extreme softness, and the black streak or mark it makes when rubbed on paper. It occurs in shining black flakes and grains from microscopic sizes up to crystalline lumps one-half inch or more in length. It may be confused with molybdenite (molybdenum sulphide) but that mineral reacts vigorously Then heated with nitric acid whereas graphite is in active. Furthermore molybdenite has a bluish tinge of color. Amorphous carbon (Gcaphiffc) .is dull aid earthy, resembling soot from a stove. Graphite is used in the manufacture of metallurgical crucibles and related products, special kinds of batteries, electric brushes and other electrical equipment, graphite paints, and certain types of lubricants. Some graphite is used in foundry facings, and there are many other uses. Graphite of various grades is produced in many countries. It occurs in many states of the United States and is produced in several. The total demand is relatively small, and in normal times about equals the supply. The price of crystalline graphite ordinarily ranges from 080 to 0200 per ton (U to 10 cents per pound), but during war-time demand, prices have been mich higher. In normal peace-time years, production of natural graphite within the United States will average about 2,000 to 3,000 tons per year each of crystal line and amorphous grades. Crystalline graphite is valued at about $60 to 090 and amorphous grades about $lli per ton} however, Uhited States production of natural graphite has flourished only in times of war when importation of high- grade foreign graphite has been greatly curtailed, and demand caused an in crease in price of the domestic graphite. Imports into the United States normally are about 2,000 to 3,000 tons of crystalline flake, 6,000 to 8,000 tons of crystalline dust, and about 10,000 tons of amorphous graphite, with respective values averaging $90, $65, and $15 per ton. A substantial quantity of artificial graphite is manufactured. Commercial grades of natural graphite should contain not less than 85 percent carbon, and 90 percent or more is desired. Most of the imported amorphous graphite comes from Mexico, whereas the bulk of the imported crystalline graphite comes from France, Ceylon, and Madagascar. . Crystal Graphite Mine The Dillon deposits lie near the head of Timber and Van Camp gulches high in the Ruby Mountains east of Blacktail Deer Creek at the end of a ridge known as Crown Point. A graded gravel road extends 7 miles south from Dillon along Blacktail Deer Creek to a good mountain road, easily traveled by automobile during dry weather, which continues 9-| miles to the mines. The western slope of the Ruby Range rises abruptly from altitudes of about 6000 feet in the main valley to 7500 feet at the mine. The range is cut by deep canyon-like gulches i 2 to 5 miles long, and bold exposures of hard rock ledges are common. The top of the range is a rolling upland, a remnant of an ancient erosion surface which ^feisted in Tertiary time* The deposits were discovered in 1899 by Mr. Robbins, a prospector, and soon sold to Mr, Pearl I. Smith of Dillon who organized the Crystal Graphite Company in 1901. The first shipment of 50 tons made in 1902, came from the Bird's Nest claim idiich lies about one mile east of the main workings on the Groundhog Claim developed mainly in 1918. Between 1902 and 1920 about 2,000 tons of graphite concentrate are said to have been marketed intermittently, most of this production being at the time of the first World War when prices ranged from lL to 28 cents per pound. In 1938 the land was surveyed, and a patent on the Groundhog claim was issued to Mr. Ralph Smith, son of Pearl I. Smith who died in 1937 The property was leased in 19U1, and operations were renewed under new management. In 19ii3 and 19UU a 1050-foot adit 280 feet below the main workings was driven, and in 19Ui a small flotation mill was ejected to treat thd run-of-mine rock and old dumps containing much fine graphite. bout 150 tons of concentrate, valued at $120 to $200 pet ton, f.o.b. DfLllon, depend ing on grade, are reported to have been marketed during this last operation. This part of the Ruby Range is composed of a complex series of gneisses, schists, and dolomitic marbles of early pre-Cambrian age. To the north of the graphite mines the metamorphic complex is definitely sedimentary in origin as evidenced by the presence of at least five marble members together with quartz ite, which were originally limestone, and sandstone. The series is considered equivalent to the Cherry Creek series# named after that locality south of Bnnis. Some of the marble members are 600 to 800 feet thick, and are the host rock for comercial deposits of talc. The top of the series on Axes Canyon is ob scured by Tertiary deposits, but not far distant middle Cambrian sediments ^^;rlie it. Ihe Belt series of upper pre-Cambrian age is absent in this part ^Montana. Apparently underlying the series is a great- thiakness of contor ted feldspar gneisses th ich may correspond to the Pony series.## In general the Cherry Credc series on Axes Creek differs in lithologic character, from the -Cherry Creek series in the type locality, particularly in the abundance of marble members, but also in sequence of rock types. The graphite occurs near the base of this series. At the mines the country rock consists of alternat ing bands of feldspar-biotite gneiss, biotite schist, and gradations in between. Garnet is present locally in the metamorphic rocks. Marble, dipping about li5N.W., is present adjacent to graphite at the east end of the dis trict, but this marble member, about 175 feet thick, terminates abruptly near the center of the district just east of the main graphite deposits on the Groundhog Claim. Many bodies of coarse- to fine-grained granite-pegmatite cut the metamor phic rocks at the mines, and one mass trending northeasterly is 100 feet wide and 800 feet long. Some of the pegmatite contains pyroxene minerals. Most of the pegmatite occurs as small vein-like stringers which stand vertical or nearly so. These pegmatites do not appear to have been deformed by regional metamor phism, and they arc probably related to the late Cretaceous or early Tertiary intrusions of Montana. A dark-colored igneous dike similar .to diabase'strikes*northerly across the graphite-bearing area and stands nearly vertical. Through most of its extent it is about 25 feet thick, but it widens to about 100 feet at its north ern end. Other dark-colored dikes arc present a short distance west ,<jf the *Pcale, A. C., Description of the I'hrce Forks sheet, Montana; U.S. (ieol. Survey, Geologic atlas, Shree Forks Folio, No. 2h, 5pp, 1896. 3 b..ntagneao:logMicoanltanreacoBnunreaaisusaonfce - 1U - \ ti*A 1*1 ___ J___ 5XK ."foO 9M'3 Hliu a<. a oV M*p4 /! -i H'r ! \ CA &_ o2 2 A. Ki' sj >/.r* -** c bsis; !! t si: a!m Oo '*.X. *1 rm rzmrnmMSMmmms / \V m za|-S8'i *8a'ssx main deposits, and a larger dike-like body of similar rock lies north of the mines about one-half of a mile. These dikes have suffered no regional metamor phism, which indicates that they are young in geologic age. Some of the peg matite has been observed cutting the dark-colored dike rock. The gene^.. strike of the various members in the metamorphic series along Axes Creek andgjtdjacent areas is quite constant N 50 E, and the average dip ranges from 7Q?^fco 80 NW. Detailed geologic structure at the mines is obscure largely because of the sudden termination of the massive marble member and the complexity of the gneissic rocks. The marble ck>es not appear to be terminated by major faulting because of the continuity of a marble member about 2,500 feet northward. Near its western termination the marble, which shows good bedding, is extremely crumpled, the small folds one inch to one fcjot or more in height forming complex patterns; however, there is little or no evidence of brecciation in the marble. It has been suggested that the presence of a large in clined isoclinal syncline with a steep northwest plunge terminates the marble. It has been suggested further that the graphite has been concentrated in a crushed zone along the axis of the fold. Heinrich (oral communication) suggests that the marble is terminated by an igneous intrusion which came into the Cherry Creek sediments prior to their regional metamorphism, and that this igneous rock was converted into gneisses in early pre-Canbrian time by the re gional metamorphism which also altered the Cherry Creek sediments- The writer favors the latter interpretation, and he sees no -evidences of-isoe^inul folding of the magnitude necessary to terminate the marble. Evidence of minor faulting such as-slickensided fissures, clay gouges, and breccias, is plentiful in the mine workings. The age of such faulting appears relatively young because of the lack of consolidation and a tendency toward existence of vugs. Occurrence and Origin of Graphite: The graphite occurs in vein-like bodies and veinlets in gneiss and pegmatite, as disseminations and irregular small masses in pegmatite, and as disseminations in the metamorphic rock essentially gneiss. Most observers use the term vein in describing the de posits because the graphite commonly lies between well-defined rock walls; but the veins are irregular in that they pinch and swell within a few inches developing "bunches" and "pockets" of graphite, and they commonly continue but a few feet, perhaps 10 or 2), both vertically and horizontally. Some may continue much farther. Many such veins are grouped together forming A min eralized zone; and the zone as whole, which may be 100 to 150 feet across, is thought to be persistent from upper to lower levels. The zone or "ore shoot" appears to plunge N 20 IS. at an angle of about U5 degrees. Locally a system of veins may^be nearly parallel, but in general there is no definite direction of strike. They cut the gneiss and pegmatite indiscriminately, and dips are alv/ays steep. Veins may split into two or three strands, aid fragments of rock may be surrounded by graphite, in general giving the appearance of a badly crushed zone. Veinlets weave in and out. The deposit as a whole roughly re sembles a stock work of graphite-filled fractures with disseminated graphite in the rock between. In thickness a vein may range from a thin film up to about one foot, and pockets of graphite six feet across have been described. Thicknesses of one to four inches are average. Late minor movements along some of the veins has caused slicker.sides in the graphite. The disseminated graphite occurs in or near the vein zones, particularly in the rock between veins. That in the gneiss is generally fine-grained and platy, lies parallel to the gneissic structure, and is interlayered with the minerals of the gneiss. It is more plentiful near veins. Graphite dissem inated in the pegmatite is coarser grained, it may be bladed and in radiating - 15 - clusters and it may occur in irregular masses or in rosettes ax inch or two cross. TShether this graphite is a replacement, or an original constituent f the pegmatite, or a filling of a shattered rock is obscure in hand specimen. The massive graphite, although clearly crystalline, does not exhibit distinct crystal shapes, but individual crystal flakes which may be one-half of an inch long may be irregularly massed together, or arranged in successive radiating clusters, or in layers of parallel flakes which have grown away from a face of rock into what appears to have been a fissure cavity. In some places comb structure and rudimentary banding have developed by graphite flakes growing in layers parallel to walls of fissures. Radiating clusters of crystal flakes which commonly have the shape of rosettes one-fourth to threefourths inch across, are conspicuous. As seen in thin section under petrographic microscope, the disseminated graphite in both the gneiss and the pegmatite occurs as crystal flakes associa ted with grains of the rock-forming minerals mainly quartz and feldspar:-(1) cutting grains in microscopic fractures, (2) "biting" into grains rcp]2cing with irregular boundaries, (3) as flakes projecting into grains and termina ting within the grain boundaries, (U) possibly as films between- grain, boun daries.'. "Where the scattered flakes arc more plentiful they become massed together forming irregular lumps of graphite in the rook. The boundaries of the lumps show many flakes extending away from the mass. In gneiss the graph ite flakes tend to be arranged parallel to the gneissic structure, but many flakes lie in random directions, in pegmatite apparent random orientations predominate, and locally a radial pattern may be developed. The grain size of the graphite ranges from microscopic specks to crystals which may be a half inch or more in length. Such conditions of occurrence of the disseminated flakes of graphite kdicates a replacement of the rock by the graphite. This, however, does not "eclude the probability that much graphite was actually deposited in open cavities and fissures. The presence of the vein-like bodies containing flake graphite arranged in layers parallel to the walls of the vein, and occa sionally banded in two or more layers, indicates cavity filling. The flakes in the layers stand at right angles to the walls of the veins. The bulk of the graphite produced so far has come from the vein-like structures. The origin of graphite is somewhat problematic ail. It is believed to have formed at depth, before this region was uncovered by erosion, through the action of very hot solutions or vapors given off by deep-seated igneous bodies. It is suggested that these solutions, hotter than the decomposition temperature of calcium carbonate (marble), caused the carbonate to give off carbon monoxide which in escaping and cooling was converted to carbon di'xide, thereby liber ating free carbon which precipitated in crystalline form. Intimate associa tion of the deposits with numerous pegmatite dikes and the close proximity of carbonate rocks substantiates this theory. The geologic age of the deposit as inferred from the probable age of the pegmatite dikes, is believed to be very late Cretaceous or early Tertiary. Confirmatory evidence of the late age of the graphite is the occurrence of this mineral elsewhere in the complex in gold-bearing quartz veins conceded to be associated with the CrctaccousTertiary intrusives of Montana (Missouri-McKee mine northwest of Ennis). Mining and Treatment: Practically all mining has been done by underground methods. tXiring tns early periods of mining, and until 19U3, adits were driven into the mineralized zone, and drifts followed the more important vqajj(jjstructures. In particular, search was made for large pockets of graphite.. .^-The ^massive graphite was dug out from veins and concentrations by means of^scrapers "^^si sting of a bent and flattened tip on a long iron rod. It was then gathered - 16 - MONTANA BUBXAU OT MINTS AND OTOLOGY KZMOIB NO. ST. PLAIT LOWER BIROS NEST WORKINGS Showing relationship of marble, pegmatite, gneiss, ond graphite. g PLAN MAP OF DUBIE LEVEL CRYSTAL GRAPHITE MINE Showing pattern of Graphite deposition Graphite "veins" from films to 10 inches in thickness SCALE ioo Feet on canvas, sacked in the sine, and taken to the surface. As graphite was scraped out, the workings were advanced, and then the cycle was repeated. Disseminated graphite ifas rejected, and that material removed to facilitate mining operations was taken to the surface and piled into reserve dumps. Such a method resitted in irregular workings and much hand labor. It also resulted in mine dunpfiwntaining ouch graphite. A total sftabout 3,500 feet of mine workings has been driven. As may be expected a co^osite map 0 f all mine workings is most complex. Four main adits from which most of the graphite was mined range in length from 180 to 760 feet, and in altitude from 7,1*10 to 7,1*98 feet. Two smaller adits were also driven. Raises and shafts connect upper and lower workings, and sane stoping was done. A shaft (now caved) 165 feet deep with workings at three levels has been sunk near the center of the graphite-bearing area. From the Antelope claim, lying immediately south of the Groundhog claim on which most of the mining was carried on, and adit has been driven northward into the mountain about 1,050 feet at an altitude of 7,210 feet which is about 200 feet lower than the main workings. It passed beneath the old working-.., but due to what is thought to be a northwest plunge (slope) in the graphite-bearing zone, no graphite was en countered directly beneath the old workings. However, graphite is present at the end of this adit, north of the upper workings, and it would be desirable to extend the adit farther into the mountain. In 19U* a 125-ton flotation mill was erected to recover fine graphite, and to treat rock containing disseminated graphite. The plant consisted of a simple crushing unit, a simple flotation unit, and a drying unit. Mill feed is reported to have contained 8 to 12 per cent graphite, and concentrates are said to have contained 85 to 90 per cent graphite (carbon). Recovery in the mill was about 85 per cent. The mill has been redesigned, and now includes a jaw-crusher for primary crushing, a ball mill, a flotation unit, a regrinding unit (ball mill), a cleaner flotation unit, a filter, and a dryer. The future plan of operation is to pass the bulk of the graphite-bearing rock through the mill. The mill is about a half mile west of the mine workings on the road to Dillon, and mill feed is trucked from mine to mill. In mining a method similar to shrinkage stoping has been followed since the erection of the mill in 191*1*, and it is probable that this method vi 11 be continued. ' An overall average of material mined since 191*1 is reported by the op erators to have assayed about 12 per cent carbon, and the same average per cent is reported for a group of 32 samples cut in the mine by a party who had no financial interest in the property. Material in the mine dumps and old gobs is said to contain 5 to 8 per cent carbon, and there is probably between 5,000 and 10,000 tons of this type of material available. Sorting out of large pieces of barren rock raises the grade. Reserves of unmined graphite-bearing rock are difficult to calculate because of irregularities in graphite occur rence, and because the graphite-bearing ground has not been entirely delin eated. Additional development work is needed to prove the existence of graph ite at a depth greater than the main workings. However, there is probably an available reserve of between 100,000 and 200,000 tons of rock of milling grade. Graphite Mine on the Bird's Nest Claim The mine on the 3ird's Nest claim lie on a heavily timbered mountain slope about h,200 feet N. 68 E. from the main workings on the Groundhog claim. A bull-dozer read leads part way to the claim. The marble which terminates to the west on the Groundhog claim passes i^-r^thwisu through the Bird's Nest claim, and adjacent to the martIs are complex gneisses and schists. Granite- -17- pegmatite is present between the two claims, and also in the mine workings on the Bird's Nest claim. The graphite occurs in the gneisses, schists, and peg matite immediately adjacent to the marble on its south side. No evidence of notable offsetting of the marble by faulting was observed. Three adits have been driven into the mountain slope the longest of which is about 270 feet in length, and some stoping has been done. Practically no timber has been placed in the mine, and the openings are still readily accessible U5 years after mining. The graphite occurs much in the same manner as on the Groundhog claim, but the veins and pockets appear to have been fewer; and a crushed zone,although present, appears to be smaller and more poorly developed. The pegmatite cuts the schist and the marble irregularly. The graphite veins cut the schist, bend in and out, pinch and swell, and appear and disappear suddenly. Graphite is present in the pegmatite and in close proximity to tho marble, but no graphite was actually observed in the marble. The amount of unmined graphite could not be ascertained, but it seems probable that much material of milling grade is present. Graphite in the Timber Gulch Talc Deposit An occurrence of graphite of much geological interest is on lower Timber Creek three miles southwest of the. Crystal Graphite mines, at the Crescent ticU mine of the Tri-State Minerals Company. The mine .lies on the lowermost slope of the mountain about one-half mile from the valley bottom of Blacktail Deer Creek. It is accessible by automobile on a dirt road which branches off the road to the Crystal Graphite mines along the east side of the main valley. Two exposures of marble, 10 to 15 feet thick and separated by about 150 eet of gneiss and schist, have in places been partially or completely altered Ro talc. The matamorphic rocks, a part of the Cherry Creek series, strike northeaster3y and dip northwest at about 50 degrees, The talc deposits have been .-opened by pits and a shallow inclined shaft to depths of 10 to 20 feet. "Crystalline graphite occurs disseminated through the talc in thin flakes up to one-eighth inch across, the quantity of graphite amounting to perhaps one-half of one per cent. The f]a kes lie parallel to one another and to the bedding of the marble; and individual flakes arc distinctly separate from each other. No commercial significance is attached to this occurrence of graphite at present. Graphite Y.'est of Dell Occurrences of graphite about 12 miles west of Dell (See fig. 3 ) in extreme southwestern Montana have been prospected, and although not of appar ent commercial value at present, should be briefly described because of in terest concerning them. The deposits lie mainly in sections 27 and 3U, T. 12 S., R. 11 7.'., on both sides of the divide between a north fork of V.ilson Creek and an east fork of Kate Creek, which in turn arc small tributaries of Muddy Creek and Medicine Lodge Creek respectively. No roads which can be traveled by automobile enter the a~ca, and it is necessary to walk one to three miles from the ends of the poor roads which follow the larger creeks. Slopes are steep and divides are 500 feet or more above the creek valleys. Only scatter ing timber is present. Numerous pits have been dug, and several adits uo to 100 feet 'S length r_nhaavvie been driven on showings of graphite by prospectors and by the fictional 'bon Company of New York City, the work having been done mainly about 1918. graphite is known to have been shipped, but it is present in dumos, and can e seen m outcrop and m float. * - 18 -, fc  - * Meet important rode formations exposed in the area are the shite crystal-line liadiaon linestone of lower Lissiasippitm age and a complex rtBasrphic series o|ttBpdsses and schists of early pre-Cambrian age. Devonian. ASlonti.tic ' liaeston^Bfepresent north of the main workings. The flp^norphic rocks have been thrown against the Mississippian limestone by a aajo^Jault of late Cretaceous or early Tertiary age (Laramide) which ex tend^ for miles in a general north to south direction. The displacement is pro bably greater than 4000 feet. Thick fault gouges as well as breccias are pre sent, and the gneiss appears crushed near the almost vertical fault tone. The fault nay be multiple, that is,composed of more than one plane of breaking. The kadisen linestone which is uniform in character from place to place shows little evidence of alteration other than recrystallization and the local occur rence of jasper. However, evidence of bedding in the limestone is indeed ob scure, and structure in the limestone is difficult to determine. The metamorphic complex in this locality, although composed of gneisses and schists comparable to the Cherry Creek series in degree of metamorphism, does not contain the same sequence of members, and the members themselves are somewhat different in lithologic types. The rocks are well banded, and the banding stands at steep angles or vertical. Strike of the gneissic banding in the area of graphite deposition is nearly due north, but local irregularities occur. In general, the gneissic series appears more basic (that is, contains more dark-colored minerals) than the Cherry Creek series on Axes Creek, and un usual types of metamorphic rocks are present. One characteristic type of Betamorphic rock is composed mainly of hornblende and may be classed as amphibolite* It may be metamorphosed pre-Cambrian dike rock. However, typical feldsparquartz gneiss with more or less biotite is plentiful and widespread. No pegmatite dikes of the Cretaceous-Tertiary type, so common in most met amorphic areas in Lontana, were observed. Also no marble members in the gneis sic series in or near the area of graphite deposition were observed, except tnat as a coarsely crystalline limestone or a marble which nay be of pre- Cambrian age is present near the mouth of Rate Creek about 3 miles northwest of the main deposits. ' The graphite is'closely associated with the fault zone, and appears to lie in the fault gouge, in fault breccias, and in the crushed gneiss nearby, None was observed in massive solid limestone, but graphite-bearing rock from pits was observed in what appeared to be breccia zones in limestone. The main fault can be traced for perhaps a mile by prospect pits dug along it for gra phite. - 19 - On the east fork of Kate Creek graphite may be observed in the hillside oat and in mine dumps of two adits 'which lie about one-half mile west of e main fault zone; however, these occurrences may be associated with a complimentary fault in the gneiss west of the main displacement. Another sim ilar deposit of graphite is near the mouth of Kate Creek 32- miles northwest of those described above. The mode of occurrence and the character of graphite are similar. Two inclined shafts were sunk to a dqpth of about 30 or U0 feet near a contact between gneiss and coarsely crystalline limestone. The graphite itself in all of these deposits is fine grained and in hand specimen generally shows as powdery black material, or in flakes too small to be clearly seen wilh the unaided eye. Under microscope many specimens show crystalline flakes 1/10 to 1 millimeter across, intimately disseminated through fault gouge and breccia, or through gneiss. The flakes lie betwesi grain boundaries of feldspar or quartz, and they may penetrate grains of these min erals. As seen on a saw-cut surface they form an intricate or reticulate pat tern of needle-like crystals (probably edges of flakes) growing in all direc tions but mainly parallel to the gneissic structure. In fault gouge, flakes of graphite are in the fine clay and in the rock fragments alike, and flakes ex tend from within the fragments to beyond their limits. Some hand samples may contain $0 per cent or more of graphite. A composite analysis of material taken at random from four different mine dumps on the Kate Creek side of the divide shows approximately 12 per cent carbon. The graphite-bearing zone appears to stand nearly vertical, and as ob served on hill slopes is continuous in the vertical dimension at least 200 feet. The graphite evidently has replaced the pre-existing minerals of the gouge, the breccias, and the gneiss; and it has been introduced into its essnt position, probably by hot solutions or vapors rising along the ruptures eatea by the large fault. The commercial possibilities of the deposits would seem to depend on the development of a suitable method of milling whereby the rock-forming minerals could be separated, because the material as it comes from the mine is not of commercial grade. Since only graphite and the common rock forming minerals are present, flotation should yield a satisfactory concentrate. Grinding would have to be fine to liberate the particles, but the rocks are soft and should grind easily, line workings are not such that reserves can be calculated. Although graphite was observed for nearly a mile along the fault zone, no doubt it is more concentrated in some places than in others. The first procedure in any attempt to exploit the deposit would be to determine the amount of milling material available, and the per cent of carbon it contains. Scattered Occurrences of Graphite Crystalline graphite is known to occur in minute flakes and small amounts in many localities in southwestern Montana, particularly in the metamorphic rocks. Generally it is not recognized due to the small size of the flakes. Commonly where talc is found microscopic flakes of graphite have been observed either in the talc or in the adjacent rocks. Graphite accompanied a gold bearing quartz vein at the Missouri-McKee mine west of Ennis. Hand specimens, generally gneiss, containing a minor amount of graphite in microscopic flakes are sent to the Montana School of lanes for identification. The node_-of occur rence appears to be similar to that previously described, and these 'Ojburrences suggest that the graphite--producing process occurred over a wide reg^ifp. How- since all of the mountains of Montana have been carefully prospected again for metals, it is unlikely that large commercial bodies of A. DENDRITIC TALC--JOHNNY GULCH B. BANDED TALC--JOHNNY GULCH C. GRAPHITE VEIN WITH PEGMATITE Crystal Graphite Mine l 1 inch L E. VERMICULITE--LIBBY Lett, unexpanded--Right, expanded F. ASBESTOS--KARST PHOTOGRAPHS OF SPECIMEN'S OF NON-METALLIC MINERALS crystalline graphite have been overlooked. If found they -would be expected to be in areas of gneiss -with corbie or limestone nearby, and the presence of pegmatite -would be an additional favorable indicator. Beds of carbonaceous and petroliferous shale up to 100 feet in thickness are present in the Paleozoic and Mesozoic series of sedimentary rocks in Montana, but the carbon in them is not in the form of graphite. Some of the petroliferous shales (commonly called oil shale) will hold a flame when heated with a match, and will yield 10 to 20 gallons of oil per ton of shale by destructive distillation. IVhen such material is crushed in large fault zones, many of which are present in western Montana, it takes on a greasy shiny black appearance, and being soft somewhat resembles graphite. A deposit of this character is reported to be present north of Melrose near Big Hole River. Little or no commercial significance is attached to such occurrences so far as graphite is concerned since the carbon could not readily be concentrated from the shale minerals v/hich constitutes the main mass of rock. This material might have some value as a mineral body in paint or other commodities. Although coal is present' in' thr yo-an0ar str:.tu' in th_- noun-tains of '.vestepn Montana, it is not definitely known to have been converted into graphite. Furthermore, the various Montana occurrences of crystalline graphite are not believed to have had any genetic relationship to deposits of coal or carbon aceous material, excepting as limestone and marble contain carbon. 21 - FART III. fEBklCDLITE <wsiii*u. *SZS V III' -f. .. ,- iawr Cenat4mlk|Wt;.;> ~: jiir . i-v - = f .; TT n<i^)n>liH ilspnalt near Libfcy, Montapa.,, tmeo^vl red as such la JV91fl,.. : is the f worked in the United States successfully on a large eo* - mercial development of this deposit, beginning in 1923, marked the initiati r industry not only in this state but in the nation* In 191*7- this ind led aver a million dollars from material mined. Although the Libby deposit is the only one being operated in Montana at present, other deposits of this unusual mineral are known in the state, and their future a waits systematic exploration and development* Vermiculite is an unusual mica-like material which receives its name from its peculiar property of expanding and opening out into worm-like forms when heated to red heat* (Latin---vermiculari, to breed worms)* Good vermiculite should expand 12 to 15 times its original volume* The mineral occurs as flat tabular greenish to bro*dsh crystals which can be separated into thin sheets, and it differs from true mica in that the sheets when bent will not spring back to their original shape* Its hardness is about 1*5 and its specific gravity 2*3 to 2.L. The simplest test for vermiculite is to heat, it and ob serve its expansion-other types of micaceous minerals will not expand* In composition vermiculite is a hydrated silicate of magnesium, aluminum, and iron in which the chemically combined water amounts to about 20 per cent* Per centage of constituents may vary considerably* The principal use of vermiculite is in heat, cold, and sound insulation* It may be fabricated into blocks, bricks, or wall board with the aid of a bind er; it may be used in plaster; and it is used for many other purposes such.a^, for packing, lubricants, rubber goods, and ip paper, inks5 and paints. Its r acoustic properties are notable* A very large quantity is used in loose form for heat and fire insulation in walls and ceilings*. It also is used as a light-weight aggregate in concrete, and plaster, and this is now the largest use of this material. It has acme practical value in its natural state, but most of the vermiculite is expanded prior to use. The expanded material will float on water. Tyler* in 1938 stated that "For expanded vermiculite the standard volume ratio is 6 pound! per cubio feet, but varieties that cannot meet this standard are likely to be used increasingly, although perhaps not at the same price per ton or even per bag." ' . As an insulator vermiculite competes with mineral or rock wool, a manu factured product made by forming fine fibers from molten rock blown into a stream of air or steam, and there are other competing materials. Vermiculite has been found and worked in several other states and in for eign countries. Deposits were discovered in North Carolina as early as 1873 and in Pennsylvania about the same time. Several deposits were discovered in Colorado about 1913, and in Wyoming in about 193S, and this natural resource occurs in otbep states* Considerable vermiculite has been mined and shipped from Colorado and Wyoming* Vermiculite is being mined and expanded in South Carolina on a large scale, and these deposits are the source of supply for southeastern United States. Large deposits of vermiculite occur in Africa; some has been shipped to the United States, and foreign producers are encroach ing on the American market. As this inconspicuous and seldom recognized min eral becomes better known, it is probable that additional deposits will be discovered. Actually the term vermiculite includes a group of similar minerals which are essentially alteration products of biotite or phlogopite (black and brown *Tyler, P. U., Minor nonmetals: U. S. Bur. Mines, Minerals Yearbook, I$38, p. 1311*. - 23 - < micas) or possibly hornblende, which are present as the ordinary constituents of dark-colored intrusive igneous rocks auoh as peridotite* However, vermi- lite is also observed in layered or metamorphic rocks such as mica schists or eisses. The cause of the alteration is uncertain; it is generally assigned to hydrothermal' (hot water) action, and bearing on this mode of origin is the regular association of pegmatite dikes with vermiculite deposits* An alter native theory for its origin is by action of weathering and surface waters; but it Beema probable- to the writer that, even if weathering has had a part in the alteration, it is subsequent to an earlier deep-seated change in the original minerals* These considerations have a bearing on continuation of deposits with depth, in that if the material has been developed by weathering, deposits would be expected to be relatively shallow, but if developed by hydrothermal solut ions, deposits would be expected to continue to considerable depth* In Montana this mineral is known to occur in several localities^ chief of which are near Libby, Lincoln County; Hamilton, Ravalli County; Pony, -Madison County; and in the Bearpaw Mountains near Box Elder in Hill County, Other de posits of micaceous minerals similar to vermiculite also are known, for example on Squaw Creek south of Boceman* All of these occurrences, except near Pony and vicinity, are of direct igneous origin, the mineral being found in large intrusive masses or dikes* The deposits near Pony and in the region southward occur in pre-Cambrian biotite or `hornblende schists.` Pegmatite dikes cut the vermiculite deposits in most oases, and they are always in the immediate vicini ty of the vermiculite* The vermiculite in the large intrusive masses appears to occur as local concentrations where dark (ferro-mhgnesian) minerals were or iginally more plentiful, or else where rones of alteration were more intense; however, certain dikelike bodies are almost all vermiculite. High grade vermi culite bodies are generally very 'irregular add more lens-like in character at ^M)by, and dike-like bodies are rarely seen* Because of its mode of origin, ^^P-miculite is to be expected-only`in the mountainous areas in Montana, as it is only in these areas that ooaditlond -suitable for its formation existed, b Vermiculthe deposits near Libby ^ie deposits of vermiculite near Libby are the largest yet worked, and a reserve for many years has been proved. They lie seven miles northeast of Lib by, and are readily accessible by automobile by traveling first for four miles east along State Highway Ho, 37 -which follows the north side of Kootenai River, and thence three miles northeast up Rainy Creek* The elevation of Libby is 2050, and of the vermiculite mines between 2,800 and 4,200 feet. Topography may be considered mountainous, and slopes which rise abruptly 1,000 to 2,000 feet above the major drainage are for the most part heavily timbered, Libby, whose population is about 3000 is on the main line of the Great northern Railway, and also on TJ, S, Highway- No, 2, Large lumber mills are at Libby, but grazing and some agriculture and metal mining are carried on in the surrounding region. Annual precipitation may reach 50 inches, and snow is deep in winter, ,- The deposits, discovered about 1915, wdre soon investigated by Mr. E, H. Alley who, Beeing the commercial possibilities of the expanded material, experi mented with the processing and utilization of the vermiculite, and he devoted time to promoting its development, a difficult task beoause the material was so little known. However, the Zonolite Company was eventually formed, commer cial production on a small soale began in 1925 from material taken ilpK shallow open^out workings* The vermioulite was expanded .in a small expansLoaiSfelaixt which been erected at Libby in about 1922* *- - 24 - * .S V The?*. but ro*et edits--'o norttaeeet Manitoba- ebtfinm.- d(Lteoeery* - la 1951 the* aa intecwmt la the Zoaellte Compasy* centrating p was erected near the mines* In 1959 tbd*t the Veraicul Asbestes Company merged to form the Univer lit# Insulation Company, leaving hut one company operating In the et. lit 1948 this company changed its name to Zonolite Company, head office'of ehiob is in Chicago, and the Zonolite Company now operates the mine* the :iMaiy'and^'ther - marketing of the product* The original concentrating1 pl*st~hae^flfcen remodeled and enlarged from time to time between 1955 and 1947, aadMUte- jfr&tess of'oon- centration changed as more improved methods were developed -The''-pkeeent'still (1948) uses approximately 1,000 tons of feed per day whioh yields between 550 and 400 tons of concentrate* The original expansion plant at- Libby has been reconstructed* . .. ' Production of crude and expanded veraiculite gradually increased as the product became better known from meager shipments in 1926 to about 20,000 tons in 1940, and 75,000 tons in 1946*' The value at the beginning of operations of the unexpanded veraiculite at the mines was approximately #12 per ton,; but with increasing volume of production, varying market oonditions, and desiand for var ious grades, prices have ranged from #8 to #13*50 per ton at the mines*' The value of expanded veraiculite (f*o*b* processing point) ranges from #*70 to #1,25 per "bag of four cubic feet weighing about 25 pounds, which iea rate of from #56 to #100 per short ton* ttining at Libby has been carried on mainly by means of open cut methods,~ the rook being dug with power shovels and Jiauled by half-track truck and con-' veyor belt to the concentrating plant which is near the mines* Selective min ing is practioed* Dimensions of the pit aret length 1209 feet; width 700 feet, maximum depth 100 feet* The concentrate is hauled by truok to Libby where it may be expanded, or as is the case with most of the material,.shipped un expanded to a plant at Great Falls and to cities in other states, Canada, and foreign countries* Several adits have been driven, and one adit 750 feet long has been driven beneath the open cut so that it crosses- the deposit at a depth of 265 feet beneath the surface* The general character of the vermiculite in this adit is not particularly different from that near the-surfe.de* ' The separation of mixed rock minerals and vermiculite has proved difficult, and several methods have been tried* Wet processes yielded satisfactory sepa ration, but was considered less economical than other methods* Flotation is not suitable for oonoentrating ooarse material* Various applications of air suction, of air lift, and of electrostatio separation were tried* At present concentration is accomplished essentially by siting and screening in conjunct ion with differential crushing, and a recovery of between 75 and 80 per cent is achieved on run-of-mine material averaging from 40 to 50 per cent veraiculite, A concentrate containing 90 per cent veraiculite is obtained. Extensive stud* ies on concentration, processing, and utilisation are being continued, ' Weight.of the unexpanded Libby vermiculite concentrate is about 55'pounds per cubic foot, and the weight of the expanded material is about 6 pounds per " cubic foot* During the process of expansion a loss in weight 6t about 10 per cent occurs, due mainly to escape of chemically oombised water* although not all of the combined water is driven off* The expansion of theorude mineral is achieved by heating quickly to a red heat (1600?.to-2000 E in 5 to 10 seconds). The material is then cooled rapidly, the rapid cooling'resulting in better plia bility and toughness to the rather brittle particles. Several types of exfoli- - 25 - ator* arteisTteoej- ItatuMTf laHy encountered ijrtexfelietieii 4a that the partly expended parttctw tlfctb d--ubstr thenstelyw and-thus prevent complete exfoli ation* hhen mi! iiialfiifc^ I expanded in an oxidizing atmosphere,. it yields a loldenxplored product+Aglne retonlag atmosphere$ tha end product is ilver- oolorad* This nh&raetaristieris important whan expanded vermiculite is used in paints, pignaata>"and inks* - ' . Geology . The general geology of the area was first studied in detail by Pardee and Larsen*, although other investigators and the writer also have studied the area. This pert of Montana is underlain by quartzite and argillite (hardened sandstone and shale) and impure liaastene of the Belt series of uppermost prstsfaabrian age. Figure 4.--Geol^jic map of Libby vermiculite deposit, Lincoln County. ps, Spokane formation? pn, Newland formation; per, Ravalli formation, sy, syenite; py, pyroxenite; v, ticrtite*roek altered to vermiculite. totaling more than two miles in thickness^ The general- regional structure at Rainy Creek is a large open syneline in which the Spokane and Newland formations (subdivisions of the Belt) lie in.the oenter* .Minor 'folding and faulting are present, and dip of strata is eowmonly 50 to 50 degrees* At Rainy . Creek in trusions of pyroxeniteand.jiyenito, together with some pegmatite,, intruded the Belt ,stgata in late Cretaceous eaf possibly early Tertiary time, aai^j^ese rocks Rainy Creek district near Libby, Montana u. S..Seol. Suni^Rull, 805 a 17*29, 1929, . pyrwri**,jy--ita j$x9about two^tkixie-mud pmw>li1 rdymm^p^jjfuly, 4ft--tn* nap, figure 4 .), The vermieulite is a oemstituent of the%f^|l--st*u4vi.* ' * - $h pyreweite* first intrusive jgt.*iri*. grsspfirs -- ft*> free*tis i1r~ damk- colored red^-h a greetgah tinge, so. altered thatrift en f iWtllieiH by. - - squeezing iM^ hands% Xa the shaller workings heljtf fnr^ hTwrtfihg evuld, bn,. drilled witlqjfeauger if eo desired, however exoavation is essentially by pow er shovels without blasting* Mineral composition of this intrusive differs- from place to place from nearly pure pyroxene (diopeide) to nearly pure bio* - tite. Alteration has produced vermieulite and in. some planes aaphibole as bestos, Apatite (calcium phosphate) containing much fluorine may constitute 5 to 10 per cent of the rock, an amount unusually high, and titanite and mag netite with ilmenite sure locally present up to 10 per cent. Feldspar is pre sent in varying amounts, generally less than 15 per oent. Vanadium is a minor constituent of some of the pyroxenite, although it is reported to he present up to four per cent in small concentrations.** The vermieulite-bearing area has been described as lying in a zone about 2000 feet wide and two miles long strik ing northerly. Hard, resistant vertical syenite dikes 5 to 10 -feat*-wide lie parallel and form "ribs" in the vermieulite zone. . Specific gravity of the pyroxenite is about 3,4. An analysis of a sample of the pyroxenite shows the following constituents calculated in terms of oxid es of metals, although of course practically all constituents are in the form of silicate minerals. .... Analysis of pyroxenite from Rainy Creek, Montana* \ v * per cent . per cenfe Silica * .................. 37.47 Sodium and potassium oxides. . 1.30 Alumina. * * * . * 2.86 Water, Ferric oxide , * 11.77 Titanium oxide ... Ferrous oxide. . * 7.83 Phosphorus pentoxide Magnesium oxide. * 10,12 Vanadium oxide ... Calcium oxide* * . 21,68 Fluorine ...... > The syenite is medium to coarse grained, nearly white when fresh, but iron- stained on weathered surfaces. In addition to the main mass are the many dikes which cut the pyroxenite, and it is suggested that the large body of syenite may actually be made up of several smaller separate intrusions massed together, Mineral composition is chiefly potash and soda feldspars with about 15 per cent muscovite locally, and accessary minerals are dark diopside and hornblende, fluorite, apatite, titanite, biotite, and garnet* The syenite differs both in texture and composition with locality, and at the south end of the stock a syenite dike containing uepheline and albite is reported. Pegmatite dikes are rather common. Three different types have been noted: (l) mafic, that is, dark colored and composed largely of pyroxene; (2) syenitic, that is, light colored and composed mainly of feldspar without quartz; and (3) granitic, that^is, composed mainly of feldspar with quartz. This order is also probably the age sequence* The granitic types axe small and most common, they cut ail rocks, of the district, and they grade into glassy quartz veins which locally contain small amounts of copper, lead, and manganese minerals* The syenitic pegmatites grade along their strike into ordinary syenite, and they *Larsen, c>. S and Hunt, Ftl Two vanadiferous aegirites from Libby,' Montana: Am, Jour, Sci,, 4th ser., vol, 36, no. 213, pp, .289-290, 1913. * Pardee, J T, and Larson, op. cit,, p, 21. - 2.7 - appear to be associated with a wide-spread wave of hydrothermal alteration which affected the pyroxenite, altering pre-existing minerals to vermiculite, asbes- and sericite mica. The vermiculite has no natural exposures, but soils in the outcrop areas show mica-like flakes, and have a yielding, slippery feel under foot. Vermi culite occurs disseminated in the pyroxenite throughout its area of exposure, and in several dike-like or irregular lens-shaped concentrations the rock may be nearly pure vermiculite. Locally, crystals (books) up to ten inches across may be irregularly massed together, but in the pyroxenite, crystals are com monly less than one or two inches across. The margins of concentrations gen erally grade into the pyroxenite, the amount of pyroxene increasing until the amount of vermiculite may be less than 10 or even 5 per cent. The concentrat ions have a nearly vertical trend, and may be as touch as 100 feet wide and 1000 feet long, although-their width is more commonly 20 to 40 feet. Slip planes cutting the concentrations of vermiculite are common, but are apparent ly much later and had quality of the vermiculite. The chemical composition of the vermiculite, as analyzed by the National Bureau of Standards, is as follows t Analysis of vermiculite from Rainy Creek, Montana Per cent Silica........................... 41.0 Alumina ..... 18.0 Iron oxide .... 7.0 Calcium oxide, , , 1.0 Per cent Magnesium oxide . . ... . 21.0 Sodium and potassium oxides 1.0 Moisture ... ...... 11.0 armation on reserves of vermioulite is not available, but it is reported to adequate for many years to come. The grade over a period cf years has met all market requirements, and there is no indication that grade will change within the .known bodies of reserve imaterrial. < ; Vermiculite deposits near Hamilton, at The vermiculite deposits on Gird Creek about 11 air-line miles east of Hamilton (see figure 5 ) have been opened only by shallow pits and short adits. Extensive tests on the grade of material (amount of expansion, etc.) have not been made throughout all parts of the area. The deposit of verniculite-bearing rock, about three miles long and one mile wide, shows promise of being commercial, and would seem to warrant additional development work. The deposit may be reached from Hamilton by automobile over about 6 miles of graded road and 12 miles of mountain road the last half of which has been cut by bull-dozer along a steep mountain slope on the north side of Gird Creek drainage. The area is near the crest of the south end of the Sapphire Mount ains, a rugged range thickly covered with timber and reaching altitudes of over 8000 feet or about 5000 feet above Bitter Root River valley at Hamilton. State Highway 57, locally known as the Sktlkaho road, crosses the range about ^2 miles southeast of the deposit; but only trails extend from the deposit to this highway. Creeks flowing east and arest from the Sapphire Range pass through deep narrow canyon-like valleys mostly inaccessable by automobile. Much of the izn&sdiate area of vermiculite--bearing rock has been thevsijjm .of 'a forest fire, and fallen timber causes difficulty in traveling. Hamilton, population about 2000, is the county seat of Ravalli |s on a branch line of the Northern Pacific Railway 48 miles south off - 28 - KfWrwrtlt/ from llrtoula to Salmon, Idaho* ' rfH py, vermiculite-bearing pyroxenite. Mining claims were first laid out on tha deposits in 1930 by .Mr,' S. H. (Swift) Chamberlain of Victor (now deceased) and associates. Prospecting by means of pits took place in the next two or three years. Hvuserous interested parties, including the Universal Zonolite Insulation Company* have examined the property. During the summer of 1948 the F & S Construction Company of Butte investigated two localities, one near the west end of the area and one on Horse Ridge,- by means of bull-doter cuts, and had samples tested for ex pansion and purity. Although the vermiculite. was considered to be *of commerc ial grade, development work was not continued because tonnage available was' in question. The vermiculite occurs in an intrusion of pyroxenite (dark-colored igne ous rock) which cuts impure limestone and argillites of the Uewland formation of the Belt series of pre-Cambrian age. Associated with the pyroxenite are intrusive masses of syenite and also pegmatite dikes. Extensive areas of . granitic intrusions (quartz monzonite) are also present in this general region, and they probably mark the eastern margin of the Idaho batholith. In general, the area underlain by pyroxenite is soil covered, but exposures of underlying rock may be observed plentiful enough to permit detailed mapping, Petrographic studies of the rock types and mineral alterations show that the Hamilton deposit is very similar to the Libby deposit in all of its gen eral characteristics, although the two deposits are 175 miles apart. Ad ditional rock types- are hornblendite and meladiorite, both of which resemble pyroxenite in hand specimen. Both magnetite and titanite (sphene) are plenti ful, the.former ranging up to 15 per cent and the latter up to 4 per cent. - 29 Apatite* is "plentiful also, -and unusual silicate minerals .such as tourmaline and titaniferous garnet may be observed* . The vermiculite (or hydrobiotite at some places) occurs as disseminations ^Pl as concentrations in the pyroxenite.' Some occurs in dike-like or tabular bodies six inches to two or three feet in width in which crystals one to four inches in diameter are present. Many of these stringer-like concentrations cut the pyroxenite. nearly vertioally. Such a condition was observed near the west end of the. area, but it is probable that similar conditions occur else where, Some basic pegmatite is present. Much of the vermiculite is fine grain ed (l/32 to l/S inch), and occurs in a more or less solid mass sparsely mixed with other minerals. Such is the case on Horse Ridge, a narrow ridge extend- 1 ing south-westward at about the middle of the area. Only trenches and pits have been dug at this location, but there appears to be a sizeable conoent- ration which grades into the fyroxenite on its margins. About one mile east of Horse Ridge additional occurrences may be observed, A 50-foot adit has been driven into a mass of the mica-like material, and vermiculite is present through out its length. Several pits halfe been dug nearby, and vermiculite is exposed in road cuts along the switch-backs which take the road to the divide of drain age. On this divide at 8000 feet altitude are more pits in vermiculite-bear- ing rock, The accompanying map (fig. 50 shows the area of dark-colored igneous rock as outlined by the prospectors who staked out the mining claims. It is their word that vermiculite may be found from place to place throughout the area. The writer has observed it across an area about three miles long. Preliminary tests show that the vermiculite from different places exhibits somewhat different ability for expansion, however material of commercial grade is present. Material from the central part of the area (Horse Ridge) which ghed 86,6 pounds per cubic foot unexpanded yielded an expanded material ghing 11.2 pounds per cubic foot. This material contained about 18 per cent-of material which did not respond to expansion processes. Another sample, small in size, had a weight of between .60 'to 70 pounds per cubic foot before expansion, and about .15 pounds pfcr cubic -foot after expansion. Before operation, .thorough sampling and testing for quality should be made fnom place to place throughout the area, and tonnages of ninable material should be determined. It is probable that success of any large-scale operat ion will require milling of the run-of-mine material to remove rock or assoc iated minerals which would be included with the vermiculite in the process of mining. Vermiculite deposits in the Bearpaw Mountains near Boxelder. , Material classified as vermiculite has been discovered and opened by pits, adits, and inclined shafts in the Bearpaw Mountains 25 miles east of Boxelder on the Rocky Boy Indian Reservation. (See figure 6) Boxelder, a town of about 300 population, is on a branch line of the Great Northern Railway 23 miles southwest of Havre which is county seat of Hill County in which the deposits lie. State highway No, 29 passes through Boxelder, Good graded roads extend from Boxelder to within 15 miles of the deposit, and easily traveled mountain roads continue to the deposit. The altitude of Boxelder is 2,682 feet, and of the deposits, which, lie near the head of the north fork of Big Sandv-teeek, is about 4,000 feet, _ Havre, the principal city in this part of Montana, has a population of ^hut 7,000. Principal industries in this region are stock raising *n2 grain 'iCr - fanning* Ho erteneiv* Binging has-' been oarriei on* although coal L present in this part of Montana,, natural gas occurs atftr Havre* . .. The Bearpaw Mountains, essentially a pile of lava and associated in- trusives on and in relatively flat-lying upper Cretaceous strata, stand out island-lijp at the western margin of the Great Plains which stretch out as a level flc<fi* for many miles in all directions. Rapidly eroding streams have cut deep feileys into the plains. ft.--showing location of vermiculite deposit in the 3earpaw mountains, Hill County. The Bearpaw fountains are unique to geologist in that the igneous mater ial which broke through the flat-lying blanket of young sediments contains un usual minerals and unusual types of rocks (potash rich). In places the strata have been bent into folds and domes, and laccolithic structure occurs. Al though this area was a seat of volcanoes, the time is so remote that erosion has removed topographic evidence of their existence, and now in the heart of the mountains only the "roots" of these eruptions are present. The deposits were first opened in 1929 when an air compressor and other machinery for mining operations were installed and cabins were built. Effort to market the material net with little success, and after a few years oper ations ceased and machinery was removed. Since the recent war interest has been revived, and during the summer of 1947 nine workings were being cleaned cut, and put into condition for operation. The vermiculite nay be observed in an open cut about 40 feet above creek level, and in an adit driven beneath the cut* Several dike-like concentrat ions which stand nearly vertical are from two or three inches up to nearly four feet in width. These have been described as basic pegmatite dikes. Al tered rock, now essentially clay, separates'the micaceous material; but at the sides of the cut relatively fresh rock (syenite and morazonite) is present. The main mass of rock comprising the intrusive in v/hich the vermiculite depos its lie is monzonite, a rock somewhat similar to granite but containing no free quartz. The deposit present in the open cuty may be traced up the steep - 31 - slope by means of pits for perhaps 200 to 300 feet. Another body of the mica like material has been opened 225 -feet west of the cut by means of an inclined ^aft. .Still other occurrences are opened by pits or adits 300 feet across ^fe valleyr but the amount of vermiculite at this location appears negligible. The material is in the form of thin dikes cutting syenite. Material from different places exhibits a difference in its ability to ex pand. That from the open cut and underlying adit appears best. That from the inclined shaft resembles biotite mica more closely. It has been suggested by operators that vermiculite of better grade is near the land surface, whereas that material farther underground has not been altered as much, and consequent ly does not expand as much when heated. This observation was not verified. In general the material does not meet the specifications given by Tyler (See page 23). Showings in the present mine workings indicate that the deposit is limited in size, but it would seem probable that with selective mining much material can be produced. Vermiculite deposits near Pony. The vermiculite deposits about U miles northwest of Pony (See figure 7) and other deposits reported in Madison County (county seat, Virginia City), are quite different from those just described in that they are alterations of a biotite or hornblende schist which is a unit within the pre-Cambrian metamorphic complex widespread in southwestern Montana. No commercial product ion has been attempted from these deposits, but prospect pits have been dug, and northwest of Pony several extensive cuts have been made by means of a bull dozer, uncovering the material to a depth of 5 to 10 feet over areas 20 to 50 feet wide and 25 to 100 feet long. Development was carried on about 19U0. Pony, population about 300, is on a branch line of the Northern Pacific ^Blilway. A good graded road extends to Pony from State Highway No. 1 at Har^rison, a small town six miles distant from Pony. Dirt roads, which are rough but passable, extend north from Pony and west from Harrison, converging to ward South Boulder Creek. The bull-dozed area lies about one and one-half milea^north of the road to South noulder Creek and three miles east of this creek. A field road easily traveled by automobile leads northward to the de posit. No prominent exposures of the vermiculite-bearing rock may be seen, although examination of the soil reveals particles of the mica-like material. The deposits lie near the divide of drainage on a gently west-sloping surface on which vegetation consists mainly of grasses and sage brush, and scattered pine trees. This region is in the northern foot hills of the Tobacco Root Mountains. The altitude of Pony is 5Wi3 feet above sea level> and of the de posits about 6500 feet. The metamorphic complex in this part of Mqdison County, generally consid ered the Pony series, consists essentially of light and dark-colored gneisses containing much quartz, hornblende, and biotite in addition to feldspar. Some zones in the gneiss contain so much hornblende that they may be considered amphibolite, and other zones are essentially biotite mica* Many bodies cf pegmatite cut the metamorphic complex, and small stringers of quartz-feldspar pegmatite are present in the area of bull-dozer cuts* The deposition of pegmatitic material is not conspicuous, probably because large bodies have not developed in this immediate locality. The-main mass of the Tobacco ftoot bathclith lies about four miles southward, but small granitic masses occur within three miles south and west. The layers of the metamorphic rocks d'HjffiO to 85 degrees northeast, and the pegmatite stringers commonly follow theS&ers. ^^^.ded quartzite, shale, and limestone of .middle Cambrian age overliw the --22 - ita&6rphic rockb about half a mile'north Of the vwrmiculite deposits* The vermiculite-bearing rock is in a zone of bypieal medium-grained-sch- 1st about one-fourth alle wide. The schist is well- layered, and in open cuts shows gheibsic bands of quartz and feldspar, these?layers being from an inch or two tegStehaps a fobt in thickness* The vermicalite obeurs- in similar lay ers, but3&fir thickness may reach several-feet. However, in the purest ma terial of quartz and feldspar, and also garnet, may be disseminated through fRe vermiculite* All of the micaceous mineral does not show equal ex pansion, apparently some not having quite reached the nvermiculite stage"of alteration. The Pony vermiculite is fine grained, average size ranging from about 1/5 to 1/50 of an inch in diameter. The mineral plates may be 5 to 6 times as wide as they are thick. Hence the expanded material is fine grained, a con dition which might limit its utilization to special purposes. The reserve is extremely large, and apparently vermiculite occurs in nearby areas not expos ed by digging. Mining operations could readily be carried on by open cut methods. The material mined v.'ould require concentration because of the large amount cf un desirable minerals associated with the vermiculite, and this amount in some - 33 - material may be half the volume. However, some zones of vermiculite are near ly pure. - Other areas of verndculite-bearing schist have been reported south of Har- near Ennis, near Virginia City, and southeast of Dillon. They have not been opened extensively by digging, and detailed information concerning them is not at hand. Some of the material examined greatly resembles the material from the Pony deposit, and it is probable that all these occurrences are much alike. They lie in the extensive area of schists and gneisses comprising the metamorphic complex of southwestern Montana* idea-bearing Jike South bf Bozeman An unusual mica-bearing dike is present on Squaw Creek drainage 15 air-, line miles south of Bozeman and about three miles east of U. S. Highway No. 191, which passes along Gallatin ftiver. (See fig. 8, p. 36). The dike is one mile up a small tributary of Squaw Creek known as Mica Creek at a point where the gulch forks. The country rock is pre-Cambrian gneiss and schist, but it is cut in many places by light- and dark-colored dikes and sills, and by peg matite dikes. A dark-colored igneous intrusion six miles south of Squaw Creek near Karst Kamp has altered into a commercial deposit of amphibole asbestos. The region is mountainous and heavily timbered. The mica-bearing dike stands nearly vertical and strikes nearly due north up the nose of a steep-sided ridge lying between the two forks of Mica Creek. It can.be traced for over 600 feet along the surface. The width of the body is variable, but near its southernmost exposure which is at creek level it ap pears to range from 10 to 20 feet in thickness. The dark-green to black mic aceous mineral, considerably altered, is the essential constituent of the dike, parts of the dike may be almost all micaceous; however dark-colored sili- minerals are also present and locally are dominant. Pegmatitic action s in the form of small stringers of quartz and feldspar cutting the dike rock. . Tie micaceous material appears to be an altered biotite or hydrobiotite. Most of it is irregularly massed together in sheets (or books) less than one- half i^ch across, but sheets two inches or more across may be observed. The * mica readily splits into thin sheets, but it is flexible rather than elastic as is the case with unaltered mica. The material upon being heated shows some expansion amounting to perhaps two or thres times, but this amount does not warrant classifying it as a vermiculite. The deposit has been opened by a short adit near creek level, and by sev eral pits and trenches spaced at intervals along the outcrop. None of the ma terial has been marketed, and there seems to be no demand for it at present. The deposit is of geologic interest, and it is illustrative of this type of dike which may be found elsewhere in western Montana. ! '. * PART IT* -ASBSSPB8 J General Considerations occurs Occurrences of asbestos have been reported at Libby, and it is possible . that unknown deposits of commercial size cure present elewhere in'Llontana. The value of asbestos lies in its unique ability to be separated into fine fibers, even as fine as 1/5000 inch across. Since asbestos is a rock-forming mineral these fibers are refractory (difficult to fuse), and are desirable for fire and heat insulation. The fibers are also acid re sisting, and of course will not decay. . . Asbestos, a name applied to a group of minerals, is broadly of the two different types, amphibole and serpentine, the latter being valued at about ten times the former. The fibers of the amphibole variety, also known as "brittle asbestos", tend to break and hence cannot be woven into clothj but mixed with a binder, such as plaster of Paris, this type is excellent for the manufacture of fire-proof wall-board and shingles, for steam pipe and furnace coverings, and many other commodities. Serpentine asbestos, also known as chrysotile, separates into fine strong silky fibers ..hich can be spun into thread and woven into a flexible cloth. Such cloth is valuable for fire-proof clothing and gloves, for fire proof curtains in theaters; but in particular for brake linings, clutch facings, and gaskets in automobiles for which most of it is used. Because of these characteristics it is much more valuable than amphibole-asbestos, but good deposits of it are not plentiful. Serpentine asbestos is a hydrous silicate of magnesium; amphibole asbestes is a magnesium silicate containing some calcium, aluminum, or iron, A definite distinction must be made be tween the two kinds of asbestos,. Asbestos is easy to recognize. As it occurs in the ground it is a hard solid fibrous mineral commonly showing pearly luster. However, small pieces can be pounded easily into a fibrous mass resembling cotton-batting. Dis tinction between the two types can be made by fluffing the mineral and then rubbing between the fingers. Amphibole asbestos will develop a powdery mass, but serpentine asbestos will roll into a thread. The two types of asbestos seldom are present in the same deposit. The . common feature of all deposits is some degree of metaaorphism, in most cases extreme. Serpentine asbestos nay occur in altered basic igneous rocks, such as dunite or peridotite, or in altered dolomitic marble or limestone. About 90 percent of the worlds supply is derived from dunite or peridotite. which have been altered first to serpentine, Amphibole asbestos may occur in altered basic igneous rocks, or in sedimentary rocks converted to schist or gneiss. Both types originate by deep-seated alteration of pre-existing rocks. Deposits of minable asbestos in the United States are limited in extent. Deposits of chrysotile have been worked or explored in seven or more states, and amphibole asbestos in nine or more states; however, total United States production is only from 1 to 2 percent of the world supply, and this country is practically dependent on imports from other countries, Canada produces about 60 percent of the world supply, southern Africa and Russia being next in importance. Total world production normaly ranges from 4G0,000 to 600,000 tons per year, of which the United States imports over 50 percent. - 35 - Price of chrysotile asbestos ranges from $20 to *750 per ton, depending on grade, and of amphibole asbestos from $10 to $40'per ton. Length of fiber, as well as , is important in determining utility and value. Asbestos deposits near Karst Location and accessibility! The amphibole type of asbestos has been mined and marketed from a deposit &2 miles southwest of Bozoman near Karst Resort on Gallatin River, Mining has been carried on in only one place, but asbestos shows at othe'r places within 1500 feet both east and west. Figure 8. --Map showing location of Mica Creek de posit and the Karst asbestos deposit. Karst is 22 miles south of Gallatin Gateway, a station on a branch line of the Chicago, Milwaukee, St, Paul, and Pacific Railway, and the nearest shipping point, U, S, Highway 191, which is oil surfaced, extends along Gallatin River past Karst, Elevation of Gallatin Gateway is 4900 feet and of Karst about 5700 feet above sea level. The area is mountainous, Th- Madison Range lies on the west side of Gallatin River, and tho Gallatin Range on the oast side, Gallatin Peak about 15 miles westward has an altitude of 10,967 feet, Gallatin River in this locality flows through a narrow steep-sided valley heavily timbered in most places. The asbestos deposits lie 2000 to 4000 feet west of the highway and river on a steep mountain slope. They are about 1000 foot higher in elevation than the river, A side road crosses the river on a wooden bridge, and continues about 800 feet to a small mill and cabins. A bull-dozer road and a foot-trail lead up the slope to the mine, and a horse trail continues on into the mountains. The deposits were discovered nearly half a century ago by Peter F. Karst who noticed the unusual mineral while hunting for deer. It is stated that about 800 tons of asbestos wore hauled on horse back down the mountain slope and then hauled to shipping points in the next few years. Larger scale development.di&mot proceed until 1935, nesyly 40 years after discovery, when the Karstolite reopened the deposit by open-cut and began development. They produced a produc^callod K lite used for wall and ceiling insulation. In 1938 the Montana J&bostoB C y began an operation which continued for two years. An aerial tram was - 36 - ieb*trdfrt#dr, attft ttev asbestos was millud and Concentrated boot river levwl, sacked,' ttd then troswported by truck to Gallatin Gateway, from where it was shipped by rail to markets, The property then remained idle until 1947 when the Interstate Products Company cut the bull-dozer road up tho steep mountain slope, andjc^parsd for commercial development, GcnertSvfieologyi The rocks underlying the area of asbostos deposits, and for sevurafiBlos around this area, are mainly a part of a complex.series of banded and^oontorted gneisses and schists of early pro-Cambrian age. They are- probably a p-rt of what is known in Montana as the Pony series, Motomorphisa is so far advanced that it is difficult to determine if thoso rocks were origin ally sedimentary or igneous, but it is probable that they were largely sedi mentary, These rocks have been intruded by dikes or sills, and most of these intrusions in turn show alteration, although not all to the same degree as that of tho containing rocks. Some dikes, waich no doubt ure to be associated with the Cretaceous-Tertiary intrusions of Montana, show no signs of alteration. Pegmatite dikes unaltered and undefornod also are present close to the asbestos deposits. Apparently th.^rc is more than ona period of diko intrusion, and some dikes may antedate the intense automorphism. The Gallatin Range east of the riv<jr is composed essentially of a thick swries of Crotucoous or Tertiary andesite flows and breccias (volcanic material) many miles in extent. Land slides of a remote date have marred the staep slope between tho asbestos mine and the river obscuring the underlying rock. They appear as rcug'nly terraced areas 50 to 100 foot wide paralleling the f.-.cc of the mountain, and they aro timbered with large trees, ; Geologic structure of tho gr-cissic complex is obscure, but 3 to 4 miles north _nd south of Karst are major faults trending northwest whose dis placement may be measured in terms of miles. In the immediate area of the asbestos deposits smaller faults cut tho rooks apparently in an intricate pat tern. The asbestos occurs in small altered bodies of peridotito, apparently dikes composed essentially of nnphibole. These bodies cannot be trocod for any con siderable distance duo to soil and slide-rock cover on the stc.ep timbered slopes, and also probably due to minor faulting. Since intrusion, alteration of the original rock has caused the development of numerous vein-lik- or stringer-like masses of fibrous amphiboly from an inch to a foot or more in thickness which cut irregularly through the dark-colored ignooua rock. Most "veins" stand nearly vertical, they strike from due north to N. 70 Yf., and many can be traced 10 to 20 feet in the face of the mine pit. The pur asbostos has grown with its fibers, which may be a foot or more in length, practically at right angles to the walls of the containing rock. Most of the fiber is straight but some is curved, particularly at ends, as though bent by earth movement. The containing rock, although superficially appearing to contain no asbestos, is in torgro'./n with disseminated fibers. In the main workings only asbestos and altered rock Wv-rc observed, but about 350 feet southward clear slender grass-green crystals, probably actinolite, were observed with asbostos. The percent of asbestos in thu asbestos-bearing rock which was mined was not accurately determined, Estinures by workmen range from 30 to 50 per cent. Also the amount of development work at the time of visitation did not permit calculation of total reserves of ~sbustos-bearing rock, however several thousand tens ware apparent at that time. Specific gr-vity of the -sb-stos ranges from 2,3 to 3,0, and its weight per cubic foot of unbroken rock is about 185 pounds. An analysis of the -sbestos stated in t--rms of oxides of elements is shown on the following table, although of- course pr_ctic..lly all of these constituents - 37 - are present in the form of a silicate mineral. Optical properties of the asbestos show it to ha-ve parallel extinction, low relief, and indices of refraction 1,67 or le8 3. These various properties indicate that the mineral is the orthorhombic iphibole known as anthophyllite. Chemical analysis of Karst Asbestos (per cent) (Lewis and l.alker, Butte, Lontana) Si02 56.0 AI2OJ 5,8 FeO 8.9 CaO 1.2 MgO 26.0 Ign. loss (h2o) 2.0 Development: The asbestos mine is essentially an open cut or pit approx imately 50 by 100 feet in plan, but it has been cut into the steep slope as a series of irregular benches, the workings having followed the better grade of asbestos-bearing rock, "Veins" of asbestos show throughout all of the pit. About 30 feet below the level of the pit floor, and 40 feet southward a 100- tfoot adit has been driven so as to pass beneath the surface workings, The first Po feet were in pegmatite, the next 40 foet were in asbestos-boaring rock, and pegmatite is at the northern end. Two faults which converge downward appear to be between the asbestos rock and the northern and southern bodies of pegmatite. A shaftn non filled, connected the adit and the pit. Sixty feet north of the pit is an unaltered vertical syenite dike trending northeastward. Immediately west and east of the pit arc exposures of gneiss. Fifteen hundred feet southeast of the open cut low down on the slope a short adit apparently driven into landslide material encountered showings of asbestos. Sixteen-hundred feet S. 75 V. of the cut and at about tho same elevation "veins" of asbestos show in an area at least 40 feet by 75 feot, and short adits have been driven. The accurrence and the appearance of the asbestos in these adits and on the dumps in front of them is similar to t at in the main pit, however some material is more inflexible and does not fluff so readily. These occur rences indicate presence of asbestos-bearing rock in an area at least 3000 foet across. . Mining and Killing: In mine operation the mixed asbestos and rock were blasted in the open cut, loaded by hand into cars, and trammed about 60 feet to a bin. Some selective mining was practiced. In one part of the pit five vein like bodies of asbestos totaling about three feet in thickness show in an eight- foot working face. Lore asbestos shows in other parts of the pit. A large dump of mixed asbestos and rock has developed in front of the pit, and much of this material is of milling grade. An aerial tram, consisting of buckets suspended on a moving cable, carried the material about 1650 feet from the bin to a small mill situated'-.^)0 feet west Ooif the river and 100 foet higher. Since the loaded buckets travelog'down grade mid the empty buckets up grade, no power was n eded to operate the 45ram, in fact akes were needed. However, a gasoline motor was used to start tho operation. - 38 - At tn* mill the material was crushad, and then passed through a hammer sill which caused the asbeetoe to- fluff and'the reck to crumble. The material was then introduced into an air classifier consisting -ef a rising column of air is a cone-shaped container. Fluffed asbestos ready-for shipment was carried oat by the adr~t and crushed rod: fragments settled to *tho bottom and were removed* The asbdray* was then sacked in paper bags and trucked to the railroad at Gallatii^feteway, In all, 1800 tons of asbestos reported to have been valued at v35 pr ton f.o.b. Gallatin Gateway are said to have been marketed. Electric power for the mill and for lighting was generated by a small hydroelectric power plant on Loose Creek on the east side of Gallatin River, about 1500 feet northeast of the mill. Serpentine Asbestos near Cliff Lake Location and development: An occurrence of serpentine asbestos (chrysotile) about 50 miles south of Ennis has been explored, and an attempt was made to mine and mill tho mineral. The deposit is in section 25, T. 12 S,, R. 2 E. nine miles by road southeast of Cliff Lake Post Office in a deep rugged gulch tributary to Kile Creek. A graded dirt road leaves State Highway No.l near the Fost Office, crosses Ladison River on a wooden bridge, and continues across terraced and rolling valley lands to about one mile of the mine where a mine road leads into the gulch. The deposit lies on the flank of a high rocky range facing Ladisor. River valley. - 39 - The deposit was discovered by Israel A. Hutchens about lb90. Shortly after 1900 the Idaho Montana Asbestos Company prospected it by driving an adit over f-eet into the iqount&in. Commercial quantities of asbestos were not found. ^Bout 30 years ^ater after reorganization and some prospecting, the i'ontbestos Company was formed. Large substantial buildings were erected, heavy and elaborate machinery both for mining and for milling was installed, and a renewed effort was made to find commercial deposits, and to separate the asbestos from the rock. The operation was unsuccessful, and in 1935 the machinery was taken av;ay, and the property was abandoned. . In all about .500 to 600 feet of. underground adits have been driven, and three large surface excavations besides small pits were made into the steep mountain slope. Hilling operations included crushing, wet screening, and cone classification, some t>y means of air. Total amount of rock put through the mill was small. Geology: The side of the mountain range in which the deposits lie is com posed of marble, gneiss, and schist, possibly a part of the Cherry Creek series of early pre-Cambrian age. The rocks of this area do not closely resemble typical rocks of the Cherry Creek series, and they may be a part of some related pre- Cambrian series. However, the asbestos occurs in a thick marble member within which one- to five-foot zones.of yellow-green serpentine were developed, apparently following along planes of shearing. Bedding is steeply inclined or vertical, and shearing planes are inclined at about 40 degrees and cut bedding. A dark- colored igneous rock (gabbro) was intruded into the marble, and although not observed in outcrop near the pits, it was encountered in mine workings which ex tended into the mountain. No typical pegmatite dikes were observed, luich dirty- white quartz, pegmatitic in character,: is.present in the marble as thin irregular stringers roughly .parallel to the shearing. Other minerals, particularly a fibrous amphibole, are-abundant locally. Some'of-the njartle appears gray because of in- uded microscopic grains of magnetite. } The asbestos occurs in narrow veinlets cutting serpentine and marble, Lost the veinlets are from l/l6.to l/2 ihch in width, and tney commonly extend four inches to a foot or two before pinching eut. Numerous veinlets may occur in a zone of serpentine running roughly, parallel to each other and to the zone. Some veinlets appear to cut pure marble^ bu*t there may have been massive serpentine present before the grovrth of asbestos. Th^ fibers in the asbestos lie at right angles to the vein walls, and extend completely across the veinlets. The total amount of serpentine in proportion to marble is small, perhaps one or two percent, and the amount of asbestos in proportion to massive serpentine is probably equally as small. The failure of the mine appears to have been duo mainly to the small amount of asbestos present; however, so far as known to the vn*iter, no long fiber asbestos is present. Asbestos near Libby Amphibcle asbestos occurs with vermiculite in altered dark-colored igneous rock (pyroxenite) near Libby. It accurs most abundantly in the northwestern part of the area, particularly on the spur north of Kearney Creek, As described by Larsen "several bodies ... are dike-like or tabular in form and of different widths. The largest, as exposed by open cuts, appears to be 100 feet or more long and from a f9W feet to 14 feet wide .... Samples representing the different bodies show the amphibole to be mixed with 1 to 10 per cent of ether minerals, chiefly vermiculite and unaltered pyroxene. In other places the country rock is particularly rich in amphibole. A sample across a width of 10 the rock as exposed by a short tunnel contains, in round figures, 75 peruJ^nt amphibole j^per cent of pyroxenite and apatite, and 10 percent of vermiculite. ~ A sample w L0 - representing another body SO feet wide consists of SO per oent azrphibole, 30 per oent pyroxenite, and 20 per cent vormieulite," - The Libby amphibole asbestos related to (traaolito) works up into * Patty mass similar to tho general run of asbestos, although the fibers are weak sad inelastic dfti break into short pieces, Weathering seeas to hare produced %" softer tyqgfcof fiber. Hilling would be necessary to obtain a commercial prod uct, and Spfc trouble might be had in separating the Termiculite. Bo asbestos has been marketed from this deposit which is worked on a large scale for rermiculite. In general it may be said that the Libby asbestos deposits are of minor importance because of small tonnage and low quatity. For a map of the area, and descriptions of the geology of this deposit, the reader is referred to the chapter on Termiculite in this report, Pardee, J, !r,, and Larsen, j, deposits of Termiculite and other minerals in the Rainy Creek district near Libby, Uontanai U. S, Geol. Survey, Bull, 805-B, p, 25, 1929. Other Occurrences of Asbestos Hand samples of asbestos, both amphibole and serpentine, have been picked up in western Montana and submitted to the Montana School of Hines for ident ification, Failure to expose large bodies of this material suggests that the deposits were small, With the large amount of igneous intrusion and meta morphism in this region, it is possible that commercial bodies still remain undiscovered. However, in western Montana every gulch has been prospected for metalliferous minerals during the past 80 years, and it would seem unlikely that so conspicuous a mineral as asbestos could be exposed in commercial deposits, and yet the deposits not be made known, - - 41 - BIBUOGRARHY Talc ... Gillson, 4* L.> Talc, Industrial Minerals and Rocks (a symposium), Am. Inst. Min/Sfeg., pp. 873-892, 1937. Klinefeltl^-' T, A., and others, Survey of the suitability of domestic talcs for high-frequency insulators* U. S. Bur. Mines, Rept. of Invest. 380U, 58 pp., 19U5* U. S. Bur. Mines, Johnny Gulch talc deposits, Madison County, Montana* Yar Minerals Report 17o amd 3k}, 19U5. (See also U. S. Bureau of Mines, annual volumes of the Minerals Yearbook). Graphite Bastir., L. S., The graphite deposits of Ceylon. . . and a similar graphite de posit near Dillon, Montana* Econ. Geology, vol. 7, pp. U19-UU3, 1912. Ferguson, H. G., Graphite in 1916* U. S. Geol. Survey, Min. Res., 1916, pt, 2, pp. U3-59, 1917. ------------------------- Graphite in 1917* U. S. Geol. Survey, Min. Res., 1917, pt, 2, pp. 97-119, 1918. (See also annual volumes of the Mineral Resources and Mineral Yearbook.) Rowe, J, P., Some economic geology of Montana: Montana Univ., Bull. SO, Geol. ser. no. 3, pp. 66-67, 1908. Miller, B. L., Graphite, Industrial Minerals and Rocks (a symposium), Am. Inst. Min. Eng., pp. 333-3U6, 1937, Tyler, P. M., Graphite: U. S, Bur. Mines Information Circulars 6118, 6122, 6123, and 612U, 1929. Winehell, A. N., A theory for the origin of graphite as exemplified in the graphite deposits near Dillon, Montana* Econ. Geolocy, vol. 6, pp. 218 230, 1911. ' ------------------------- Graphite near Dillon, Montana: U. S. Geol. Survey, Bull. . U70, pp. 528-532, 1911. ------------------------- The mining districts of the Dillon quadrangle, Montana: U. S. Geol. Survey, Dull. $7k; pp. 105-110, 191h. Vermiculite Hagner, A. F., YVyoming vermiculite deposits* V.yoming Geol. Survey, Bull. 3U, I U7 pp., 19liii. Kujawa, R. J., Studies on the mineralogy of the Libby vermiculite deposits, Montana, Montana School of Mines, Thesis (B. S.), 32 pp., 19L2. Kriegel, Y>., Summary of occurrence, properties, and uses of vermiculite at 1 Libby, Montana: Am. Cer. Soc., Bull, vol. 19, pp. 9L-97, 19L0. Larsen, E. S., and Hunt, V.. F., Two vanadiferous aegirites from Libby, Montana: Am. Jour. Sci., iith ser., vol. 36, pp. 289-296, 1913. Pardee, J. T., and Larsen, L. S., Deposits of vermiculite and other minerals in the Rainy Creek district near Libby, Montana: U. S. Geol. Survey, Bull. 805-B, pp, 17-26, 1929. Prindle, L. M., Kyanite and vermiculite deposits of Georgia: Georgia Geol. Survey Dept. Forestry and Geol. Devel., Bull, L6, 50 pp., 1935. Tyler, P. il., Minor nonmetals: U. S. Bur. Mines, Minerals Yearbook, 1936, p. 1072. (Also s^e other annual volumes of the minerals Yearbook). ] (See also U. S. Bur. Mines, Information Circulars 6205 (1929), o720 (1933), 7270 (19UU), and 7388 (19L6). I | ( \ t i i l< i I Asbefiio6 pwles, 0., Asbestos * U. S. Bur. Mines, Bull. U03, 1937* ---- -- Asbestos, domestic and foreign deposits: U. . Bur. Mines, Inf. Circ. 6790, 2k pp. 1931:. ----------------- and Stoddard, B. H., U. S, Bur. Mines, Minerals Yearbook, 1935* pp. 1115-1123, and Minerals Yearbook, 1936, pp. 989-995. (See also other annual volumes of the Minerals Yearbook). Ross, J. G., Asbestos (with bibliography), Industrial minerals and Rocks (a symposium). Am. Inst. Min. Eng., pp. 75-96, 1937. Taber, S., The genesis cf asbestos and asbestiform minerals (with discussion): Am. Inst. Min. Eng., Trans., vol. 57, pp. 62-98, 1916. - U: - Asbestos wles, 0., Asbestos: U. S. Bur. kines, Bull, U03, 1937. ----------- Asbestos, domestic and foreign deposits: U. . Bur. kines, Inf. Circ. 6790, 2h pp. 193U. ----------------- and Stoddard, B. H., U. S. Bur. Mines, Minerals Yearbook, 1935, pp. 1115-1123, and Minerals Yearbook, 1936, pp. 989-995. (See also other annual volumes of the Minerals Yearbook). Ross, J. G., Asbestos (with bibliography), Industrial minerals and Rocks (a symposium), Am. Inst. kin. Eng., pp. 75-96, 1937. T-aber, S., The genesis of asbestos and asbestifora minerals (with discussion): Am. Inst. Min. Eng., Trans., vol. 57, pp. 62-98, 1916. i - uu -