Document J3ZD59d24orEYKNwKxrKgR3yX

thJhldbu+J f *h */ . L*f,rJ ms, jlfzJt-x___ fu?_ \ s^o- f l> , Asbestos R. W. WINSON $ Asbestos is the generic name given to a group of fibrous mineral silicates found in na ture. -They are ail incombustible and can be separated by mechanical means into fibers of various lengths and cross sections, but each differs in chemical composition from the others. The commercial grades of asbestos consist of a spectrum of lengths and sizes and are not definitive as are most organic fibers. It is generally recognized that there are two main groups of asbestos. The first only con tains the fibrous serpentine called chrysotile and comprises about 94% of the world production of asbestos. The second group contains five minerals in the amphibole series--crocidolite, amosite, anthophyllite, tremolite, and actinolite. The latter two have no commercial importance. Previous editions--1937, 1949, and 1960-- have developed a format describing the general physical properties of asbestos, the distribution of deposits throughout the world; description of mining and milling methods, tests and specifica tions, grades produced, prices, uses, and mar kets. In this edition, certain phases are discussed in more detail. The sections relating to world occurrences, geology of deposits, and methods of evaluation are more fully covered. Statistics have been augmented and up-dated whenever possible and the bibliography enlarged. t The author wishes to acknowledge the as sistance of J. W. Axeison, Research & Develop ment Center, Johns-Manville Corp., Denver. Colo., in the revision of the section on physical properties; also the help of E. L. Mann, Explora tion Oept, Canadian Johns-Manville Co. Ltd., Asbestos, Quo., for the updating and expansion of the section on occurrences, geology, and evaluation. Acknowledgment for assistance in preparation of the sections covering mining, milling, uses, and markets is gratefully made to J. N. Gauthier, E. 8. McKenna, D. P. R. Smyth, and R. T. Hughes, respectively. t Mine Project Manager, Canadian Johns-Manviile Co. Ltd., Asbestos. Que., Canada. Properties Physical The structures of asbestos fibers have been studied intensively over a number of years. X-ray diffraction patterns have been used as a means of identification and classification. Low angle .X-ray scattering techniques have shown that chrysotile fibers are "hexagonaily close packed" and parallel to each ocher, having cross-sectional diameters varying from 180A to 300A units, while the amphibole fibers are many times larger in cross section. Electron micrographs of the more common types of as bestos are shown in Figs. 1-4. Fig. 1 illustrates the softness and flexibility of chrysotile which make it suitable for textile-type products. For a number of years there was consider able controversy over the exact nature of chrysotile fiber, but the photographic evidence in Figs. 5-7 cleariy show that it is tubular in structure. The curvature is the result of the mismatch in the dimensions of the silica [SijO,] and brucite (Mg(OH),] layers which are on the inside and outside, respectively, of a double sheet. This curvature had been pre dicted by Pauling (1930) years ago based on the molecular dimensions of the two com ponent structures. Chemical Composition The theoretical compositions of the six grades of asbestos are given in Table 1. It can readily be seen that the basic structure of all five min erals in the amphibole series is the same. The only difference is in the amount and type of metallic cations present. Consequently, all the amphiboies are quite similar but do differ sub stantially from chrysotile. The idealized formula for the different types of asbestos are given in Table 1, but the actual compositions are different because of various impurities and differences in the chemical com- SISS'liO lS FIG crogra XSOOt proxst repro< ST07U56I7 tine rock, and it is only natural that there will be imperfections within the crystal structure and the inclusion of impurities between libers and at the ends of the fibers near the wall rock. It is very difficult to remove these impurities by mechanical means, so they are present in the final product. Generally, they do not have any significant effect on the use of asbestos; but in TABLE 1 --Types of Asbestos Type Chrysotile Hydrated magnesium silicate Crocidolite Complex sodium iron silicate commonly called Blue Asbestos Amosite Iron magnesium silicate--same as anthophyllite except for high iron content Anthophyllite Magnesium silicate with varying amounts of iron in the lattice Tremolite Calcium magnesium silicate Actinolite Calcium magnesium silicate with varying amounts of iron Theoretical Formulae Mg, [(OMI.SijO, 1 , Na,Fe, KOHIS..O, , ] , MgFe, [(OHISi.O, , 1 , (Mg.Fe), [(OHISi.O, , ], Ca, IMg.Fel, KOHISi.O, , ] , Ca,(Mg.Fe), [(OHISi.O, , ) , riMirrn ad-vt :he S.o, . WgO. ` F *0 F e. O , Aij'O,' H.O. ' CaO. * \a. O CaO - mcrograph oj XSOOO. Reely 33% in Asbestos 381 8 I 9snz.ui s hat there will seal structure >eiween fibers the wall rock, impurities by iresent in the not have any bestos; but in at Formulae .0,1, B'.O, ,1, H(0, , 1 i -IIS..0 UOHISi.O, , 1, HOHIS..O, , I , a few cases, such as electrical applications or some filtration systems, the amount of impuri ties has to be limited. Crocidolite and amosite occur in metamor phosed siliceous-ferruginous sediments. The fi bers are often comparatively long, ranging up to several inches. These long lengths have no advantage for most uses and may detract from the value, since the greatest use is in asbestos cement products where fiber lengths of ' to -Hi in. in length are more suitable. Anthophyllite (Rabbit, 1948) has a low ig nition loss comparable to that of tremolite. It is never known to occur with fibers sufficiently flexible to be spun nor with the tensile strength required to make them of value to the asbestos cement industry. Resistance to chemical re action opens a specialized field for this fibrous SiO,. % MgO, % FeO. % Fe, 0,.% Al,0,, % H j O, % CaO, % Na,0. % CaO * Na,0, % TABLE 2--Apprommata Chemical Analysis of Asbastos ChfYSOtti* Crocidolite Amosite Anthophyitite 37-44 39-44 0-6 0.1-5 0.2-1 5 12-15 tr-5 -- - 49-53 0-3 13-20 17-20 - 2.5-45 - 4 0-6.5 - 49-53 1-7 34-44 - 2-9 2-5 - - 0.5-2.5 56-58 28-34 3-12 - 0.5-1.5 1-6 - - - Tremoitte 53-62 0-30 15-5 1-4 0-5 0-18 0-9 BRAKEGATE iwnnj IDiuiro id do ui/j vny., ftlOSAJtj) \Q W--'* `)IJ s*- <MOqs apio {eujj^qx t 3NC1 u> 4 J*> Mi6l josurdiuos w jnjauau uoiunpouljj ut .({Jioi.itrojddo pjjnpjy 000SX oiSjoiq I.tydoifiuy--f Q[j ST07456 I 9 toiiitipojdjj *ioutixojddo OOO'OStX -S 91J tioiunpojdjj u! > fC <l*iowixojd -do pijnptx QOOiX vjufy ifmo$ `3Su3j ilisotuy -- 5[j s>poy pue s|ej9U||/^ |eu;snpu| Z2Z BRAKEGATE hmitfo 3 -- A mo si t e. South A fried. Reduced apuely 33% in etton. Asbestos 383 ST07I.5620 4--Anthophyleorgia. X5000. 'd approximately i reproduction. mineral as a filter medium and as a filler. A comparison of the general properties ( Badollet. 1951 ) of the six varieties of asbestos is given in Table 3. Thermal analysis (Pundsack, 1955) of chrys olite shows a broad endothermic peak between 600' and 720C, which corresponds to the loss of structural water and an exothermic peak at SOO'C associated with a phase change to fosterite. The hydrogen ion concentration of chryso lite has been reported to vary from 9.0 to 10.3, depending on occurrence and method of mea surement. A value of 9.7 will be most typical. FIG 6--High resolution electron micrograph ot chrysolite. Reprinted with permission from Acta Chrystalogica." ( Yada. 1967). Reduced approximately 38% in reproduction. FIG. 7--High resolution electron micrograph of chrysolite. Reprinted with permission from Acia Chrystalogica." ( Yada, 1967) Reduced approximately 389c in reproduction. BRAKEGATE MMITFO 386 Industrial Minerals and Rocks The hydrolysis of chrysodle in distilled water free from carbon dioxide resembles the action of magnesium hydroxide. Chrysotile is unique as compared to the other types of asbestos and most materials of a simi lar nature such as clays and talcs, since it car ries a positive charge or has a plus zcta poten tial in a water slurry. The magnitude will vary with chrysotile from different deposits. Simi larly. the isoelectric point or pH for zero po tential will be dilferent for chrysotilcs trom various sources. The isoelectric point for chrys otile will vary from 10.5 to 11.3 depending on the source of the fiber and the method of measurement. Careful density measurements I Pundsack. 1956) of chrysotile have shown values ranging from 2.53 to 2.58 with 2.56 most typical. The surface area determination of chrysotile depends upon the type of measuring apparatus employed. The industry generally uses an air permeability method ( Badollet. 1951 ) for mea suring the degree of openness of the fiber. If the true surface area is desired, it is necessary to employ gas absorption techniques. Specific areas by air permeability will range from about 0.4 to 5 sq m per g. whereas comparable gas .adsorption areas will vary by a factor of 10 from 4 to 50 sq m per g. depending on the source of the fiber and the degree of openness. Effect of Heat on Asbestos The weight loss for different types of as bestos when heated for 2 hr each at successive temperatures from 400' to 1 800 F is shown in Tabic 4 (Badollet. 1951; Badollet and Streib. 1955). As expected, the weight loss for the amphiboles is considerably less than for chrys- TABLE 5--Effect of Meet on Tensile Strength of Cenedien Chrysotile Crude T ensile Strength. Psi %of Original Tensile Strength Original crude. no heat Heated 3 mm at 600JF Heated 3 mm at 800 F Heated 3 mm at 1000F Heated 3 mm at 1200F 131.000 120.000 96,000 78.000 42.000 _ 91 6 73 3 59 5 32 0 otile because of much less available OH to be driven off as water. In spite of this, the am phiboles after heating at 800F will still be more brittle than a chrysotile heated at 100' to I 100'F. Table 5 shows the effect of heating chrysotile on the tensile strength of the fiber. The fiber bundles tested for tensile strength were very small so heat transfer would be effected in the 3-nnn heating time. Even after heating at I200'F chrysotile retains 32^ of its strength. Chemical Resistance Asbestos is often used in chemical service where resistance to chemicals is of paramount interest. Table 6 gives data on the effect of various acids and caustic soda on asbestos after long exposure at room temperature and for short exposure at boiling temperatures. Be cause of the basic nature of chrysotile. it is seriously attacked by strong acids and should not be exposed to them. It is resistant to 25^ caustic but recent data show that it is attacked by strong caustic (705F ) at its boiling tem perature. TABLE 4--Effect o( Temperature on Low in Weight of Asbestos Fibers \ Loss m VVt T >me. F Hr Amosite Antnoohv'itte Chrvsotfle Crocidohte 400 600 700 800 900 1000 1 100 1200 1400 1500 1600 1 700 1800 2 2 2 2 2 2 2 2 2 2 2 2 2 0 23 0 57 0 80 0 98 1 07 1 16 1 36 1 39 1 43 1 52 - 1 53 0 05 0 24 0 30 0 38 0.4 1 0 44 0 52 Q 54 0 54 0 64 1 12 1 73 2 39 0 30 0 85 1 78 2 17 2 83 3 99 10 38 12 75 13.43 - 13 62 - 13.77 0.08 0 25 0.49 0.73 0 83 0 86 1 00 1 04 1 03 - 0 93* - 0 77- * Iron changing in weight due to oxidation. Tremoiite 0 04 0 08 0.13 0 22 0 26 0 29 0 37 0 37 0 47 0 56 0 67 1 40 2.18 BRAKEGATE UMITFO ST071.5623 C Ge Strength % of Origin** Ttnsit* Strength 91 6 73.3 59.5 3? 0 -OH to be us, the ammil util be led at- 100' ig chrysotile The fiber i were very ected in the heating at its strength. ucal service I paramount he effect of sbestos after are and for atures. Bevsotile. it is and should lant to 25% c is attacked boiling tem- T remoiite 0 04 0 08 0.13 0 22 0 26 0.29 0 37 0 37 0 47 0 56 0 67 1 40 2 18 ActmoMe Amosite Anthoohytlite Chrysotile CroadoMe T remoMe Actmolite Amosite Anthophyllite Chrysotile Crocidolite T remohte * HC1 20 31 12 84 2.66 55.69 4 38 4 77 HCl 22.55 12 00 2 13 56 00 3 14 4 22 Asbestos TABLE 6--Solubility of Asbmto* % Loss m Wt. Refluxing 2 Hr, 25% Acd or Caustic CH,COOH H ,PO. H.SO, 12.28 2 63 0 60 23.42 0 91 1.99 20 19 1 1 67 3 16 55 18 4 37 4 99 20 38 11 3S 2 73 55.75 3.69 4 58 % toss m Wt, Room Temperature 26C for 528 Hr, 25% AciO or Caustic CH,COOH H ,P04 H.SO. 12.14 308 1 04 24 04 1 02 1 41 20.10 1 1 S3 3 29 56.45 381 4 89 20 60 1 1.71 2.90 56 00 3 48 4 74 387 NaOH 9 25 6 97 t 22 0 99 1 35 t 80 NaOH 9 43 6 82 1 77 1 03 1 20 1 65 Geology General Chrysotile constitutes about 94% of the cur rent world production of asbestos and. of this amount, all but a fraction of a percent is de rived from deposits whose host rocks are ultrabasic in composition (Berger. 1963: Bateo. 1969: Keith and Bain. 1932). This other frac tion of the chrysotile production is derived from serpentimzed dolomitic limestone. Among the other varieties of asbestos, amosite and crocidolite are found in certain metamorphosed ferruginous sedimentary formations and. to gether. account for some 5.3cc of world pro duction. Tremolite and anthophyllite make up the balance of the production and are gen erally found m association with highly meta morphosed ultrabasic rocks. The bulk of world chrysotile production comes from Canada and the USSR. Southern Africa, including Rhodesia. Swaziland, and Transvaal, is the third largest producer with the balance coming from other parts of the world. Of the Canadian production, by far the greatest amount comes from the Eastern Town ships of Quebec (Fig. 8) with northern British Columbia, the Yukon Territorv. Ontario. Ungava. and Newfoundland contributing the bal ance. Russian production comes mainly from the Bazhenovo district in the central Urals, the Dzhetscara area of northwest Kazakhstan and Irom Akiovruk near the Ycncset River west of Lake Baikal. The age of asbestos deposits varies greatly from earliest Precambrian in Rhodesia and Swaziland to Upper Jurassic in California. The Ontario. Ungava. and Brazil deposits are all Precambrian. while those of the Eastern Town ships. Vermont, and Newfoundland are all as cribed a Mid-Paleozoic age, associated with early folding in the Appalachian Mountain belt. The deposits of western Canada are con nected with mountain building in the Late Paleozoic while the Russian deposits vary from Early Paleozoic to Late Paleozoic or Triassic in age. Structures General deformation in the form of faulting, folding, or shearing evidently plays a major role in the localizing of asbestos deposits l Cooke. 1940). The introduction of swarms of small intrusive dikes of acidic to inter mediate composition also contributes to the general fracturing and opening up of the rock which, in turn, leads to serpentinization and the formation of chrysotile fiber. The majority of chrysotile ore deposits tend to occur in serpentimzed peridotite rather than dunitic host material. This is probably due to the fact that serpentinized dunite bodies tend to llow when subjected to stress, thereby aiding in the development of fracturing in the sur rounding more brittle peridotite. E'AXEGATE HM1TF0 *iZ9G'i/.ulS iable. M osi tones which i with dolo- rhe Woodsit is located y 340 miles New South is of serpenid 1 '-'i miles i Serpentine body occurs nplex which ileozoic age. ; and 250 ft n margin by Strong shear e fiber zone. :ockwork of short to menmenced in t is exported * geology of tos deposits t by various awever. vari: that China with 220.000 , situated apf Peking, was chrvsotile in to the Shihix 250 miles zcchwan (the ct "rock col aw contribute which totals short chryso- kto recovered aonmg which st of Peking. lon (private Judes chrysowe crigin, toetiea. 4 in southern i of Calcutta, haction. Here separate dis Asbestos 397 continuous zones alonjf highly serpentimzed contact zones between massive serpentmized peridotite bands and massive to sheared "clot" peridotite. One of these, the Upper Zone, is economic and contains from 7% to 15% fiber over minimum mining widths. The ore is handcobbed and sorted for milling. Japan: Chrvsotile asbestos is mined at two localities in the Yamabe district of Hokkaido. Japan (Rowbotham. 1970). The fiber is gen erally short and all of the production is utilized locally. Chrysotile in Dolomite In addition to the large deposits of chrysotile asbestos found in serpentimzed peridotite there are comparatively small tonnages mined from serpentimzed dolomitic limestones (duToit. 1946: Hall, 1930: Pelletier. 1964; Rowbotham, 1970; Van Biljon. 1964). Such fiber is often of high quality and is free of the magnetite found associated to a varying degree with de posits where the original host rock is of ultrabasic igneous origin. Chrysotile of this type has been mined from the Carolina district in the Transvaal and in the Salt River and Sierra Ancha regions in Arizona where it is found in narrow bands associated with diabase sills. Crocidolite and Amosite Both crocidolite and amosite occur in South Africa (Cilhers and Gems, 1964; Cilliers et al.. !964;duToit. 1946: Frankel. 1953; Hall. 1930: Keep, 1961; Pelletier, 1964) in bedded meta morphosed sedimentary formations known as banded ironstones, that may be classed as ferruginous quartzite or probably more ex actly as an iron-rich silicified argillite. Cross fiber veins are found as closely spaced ribbons roughly conformable with the bedding which in some localities is distorted and steeply dip ping. Crocidolite veins are generally less than 2 or 3 in. thick with the bulk of the fiber be tween in. in length. Amosite veins on the other hand often range up to 10 or 12 in. thick. Crocidolite is found over a large area of Cape Province occurring in a belt of the Lower Griquatown series of the Transvaal system. One of the oldest producing areas is in the vicinity of Prieska on the Orange River with notable production coming from Westerberg and Koe- gas. located a few miles down the river. An other producing area of blue asbestos in the Cape Province is farther north in the Kuruman district, and at Pomfret. just south of the Bot swana border. Approximately 200 miles to the east and north of Johannesburg both crocidolite and amosite are found in similar formations in the vicinity of Pietersburg in northern Transvaal. In some places here the two varieties have been known to occur side by side in the same vein. Such a vein, having fibers composed of crocidolite at one end and amosite at the other, is referred to as a "doublet." It is interesting to note that there is generally no weakening of the fibrils at the point of contact of the two varie ties of fiber. In the Pietersburg area a quite silky-fibered phase of amosite called "montasite" is found which is often a dusty blue in color and has sometimes been contused with crocidolite. Widespread occurrences of amosite and crocidolite have recently been discovered m the Bababudart Hills north of Chikmagular in Mysore. India. Both varieties of fiber occur m an assemblage of banded ironstones and shales similar to those of northeastern Transvaal but the amosite in particular is noticeably shorter. However, one area of amosite has been inten sively investigated for possible production. Deposits of cnAlolite are found in the Hammcrslev rangdfl^ttstern Australia, as well as in Bolivia and cTsS^ere. Amosite-bearing banded ironstone crops out for a distance of over 20 miles near Penge in the Lydenburg district of the Transvaal. The fiber-bearing "reef" is being worked at three points along the strike, at Penge and at the Weltevreden and the Kromellenboog mines. A good cross section of the country rock has been exposed by diamond drilling to 1000 ft in depth. The fiber-bearing banded ironstones and associated sedimentary members dip southwestward at about 20. This sequence has been intruded by thin persistent sills of dolerite which are conformable with the bedding. The following column is from a 1200-ft diamond drill hole intersecting the fiber-bear ing horizon at a depth of 1000 ft below the surface at the "Amosa" mine which is part of the Penge property Shales Dolerite sills Shales Bevetts conglomerate Banded ironstone (main fiber zone) Dolerite sill Banded ironstone (sometimes fiber-bearing) Dolomite ERAKE6ATEIIMITFD Asbestos 399 nounts of antremolite. and 'file. ayllite deposits, rtanl producer. i erally coincides withjhe earth's ma|or chains of mountain building of all ages. This is par ticularly true of the Urals, the Appalachians, and Rocky Mountains, but the relationship is more difficult to recognize in Precambrian fold been climbing steadily during the period under consideration. This has been brought about by the enlarged capacities of many plants and the opening of new mines such as Advocate. Reeves, Clinton Creek, and Asbestos Hill which n the parish of belts. have more than compensated for the closing of astern Finland, t Mal]asalmi in i Production exhausted properties such as the Munro, Nicolet. and Flintkote mines. to the east. j According to the latest statistics, the Eastern teriae of lenses j Of (he world's two leading producers, both Townships of Quebec accounts for over I 3 mil ired ultrabasic { the USSR and Canada (Hendry, 1972) have lion tpy of fiber. This represents approximately be dunitic in I vast reserves of chrysotile fiber: though, fom SIT) of Canadian production, with the balance ar to have be- j the limited information available, it would ap coming from the Yukon Territory (6.0%). ties during an pear that Russia has more reserves than Can British Columbia (5 3%). Newfoundland non. The ser- ada. Elsewhere in the world, reserves seem to (4.7%), and Ontario (2.7%). The Jelfrey cur in fjiiotite be fairly evenly distributed among those coun mine at Asbestos is the largest single producer, Late KJrelian tries presently producing, or those in which accounting for some 600.000 tpy of fiber. The potential deposits are known (Table 7). balance of the production, amounting to ap enerally small, agth and 30 to yield between - The production ot fiber, including both chrysotile and the various types ot amphibole asbestos, has been steadily increasing over the proximately 750.000 tons, comes from a num ber of mines located in and around Thetford M incs. anthophyllite last 10 to 15 years (Fig. 10). Of particular African production ranks third in world pro note is the lead taken by the Soviet Union in duction statistics. It should be remembered, bodies is diffis drift-covered the mid-sixties. However, it is interesting to note that some authorities consider this figure however, that this production comprises 190.OOO tons of chrysotile produced in Rhodesia, not exposed at to be biased by the inclusion of a greater pro portion of very short fiber grades not presently the Republic of South Africa, and Swaziland, as well as 160.000 tons of crocidolite and die* is by open at a centrally recovered in Canada. Russian production of medium and short 60 000 tons of amosite produced in South Africa. It should also be pointed out that the fiber chrysotile is concentrated in the Central figures given for Rhodesian chrysotile produc reported from "Urals where the large ' Asbest" combine, to tion are estimates only, as no official produc avia. Bulgaria. gether with smaller mines and mills at Aly- tion statistics have been issued since the Rho > known of the pavevsk. Nizhnitagil. Kiyembay. and south of desian Unilateral Declaration of Independence posits or their Sverdlovsk, are capable of producing about in 1966. Rhodesian production is anticipated I 5 million tpv of fiber. Production has been to increase considerably as a large expansion .Hite is mined steadily increasing in the sixties, both at existing program has been completed at Shahanic. sintv in North mines and at new nulls at Dzhetygara in north Recent estimates place China as the fourth as been small west Kazakhstan. Aktovrak in the Tuva SSR. major producer of asbestos in the world. Pro be increasing and at Molodezhnoe and llchirsk in the Buryat duction is estimated at 175.000 tons in 1971 vn to occur in SSR. Other deposits such as that discovered at and 220.000 tons in 1972. Bugetsaysk in Kazakhstan await development European production has shown only minor nrtited quantity . There are no less than six large mills in the fluctuations over the past 15 years. Most of the small deposits Asbest" combine, the sixth being commis mines arc relatively small and production tends oodrio district sioned recently. Combined capacity of these to fluctuate. Italy leads European production i. Reports of mills is now thought to exceed l million tpv with 146.(MX) tons of fiber, most ol which is om the Aosta J The first stage of the Dzhetygara combine in mined at Balangero. French production has all lian Alps, Kazakhstan was completed in 1965 but its full but ceased with the closing of the Corsican fibrous actino- productive capacity of 500.000 tons of fiber has asbestos mines. extremely Itm- probably now been achieved with the comple The United States ranks sixth in world pro tion of a second stage of development and duction with 131.000 tons in 1971 and 132.000 expansion. ions in 1972. Most ot this production comes The first stage of the "Tuvaasbest" combine from California and Vermont with a small major asbestos as briefly dethese deposits bur closer excurrence gen- at Aktovrak came into operation in 1966. Fur ther expansion has been under construction which, when completed, should give a total capacity of some 500.000 tpv of fiber. The graph showing Canadian production has amount from chrysotile in dolomites mined in Arizona. Overall production took a noticeable increase in 1963 and 1964 when the CoalmgaNew Idria deposits were first developed. Most other countries show little change in 9Z9G'i L01S BRAKEGATE L1MITF0 404 Industrial Minerals and Rocks Geophysical Owing (o the lack of outcrop within areas of uitrabasic rocks, or within a belt in which these rocks are expected to occur, both aeromagnetic and ground magnetic surveys (Conn, 1967; Low. 1951) are often employed in the early stage of exploration for asbestos. Ground mag netic surveys may be used to check and define in more detail anomalies obtained by an air borne survey of a large area, or the ground survey alone may be used for the purpose of exploring a small area. In the case of an airborne survey, flight lines are normally spaced at '/i-mile intervals, and flown as close to 50O-ft elevation as possible. Where the terrain is rugged, helicopters are used which are capable of maintaining a con stant altitude of 300 ft above ground level. The spacing between profiles on a ground survey is usually 200 or 300 ft and readings are taken at intervals of 50 or 100 ft. Magnetic surveys are used to locate and de fine the areas of uitrabasic rocks and, within these, the areas which have been subjected to extensive serpentmization. This is possible be cause this type of alteration produces a higher content of secondary magnetite. Asbestos de posits in uitrabasic rocks are a result of inten sive serpentimzation, and for that reason asbes tos veining is usually accompanied by a higher concentration of magnetite than is normally found in the barren serpentine. It follows, therefore, that magnetic anomalies obtained over an area of uitrabasic rocks are favorable places to explore for asbestos. Figs. 11 and 12 show the results of ground magnetometer sur veys carried out over two known ore bodies. Modern instrumentation has made great strides in recent years, and it is now possible to conduct precise surveys with small lightweight magnetometers, in contrast to the cumbersome equipment used in the past. Diamond Drilling Diamond drilling is normally employed to probe beneath the overburden to assess and define the limits of an asbestos deposit. As as bestos ore bodies are usually large in volume, it is customary to drill vertical holes on a grid pattern. In the initial stages of exploration an interval of 400 ft and sometimes more may be used, filling in to an interval of 100 ft or even less, where an asbestos-bearing zone is en countered. in cases where deposit is elongated in one direction, holes are generally spaced at closer intervals across the strikes. Narrow, FIGS. 11 and 12--Results of ground magnetometer surveys of two inown ore bodies. 6RAKEGATE UMITFO ton asbesr a higher normally ( follows, obtained favorable 11 and 12 -neier surre bodies, ade great xxsible to ightweight mbersome iployed to assess a<| sit. As-** m volume, . on a grid oration an ire may be ft or even me is en; elongated spaced at Narrow, ;wmua bodies. Asbestos 405 tabular targets are best ex[flcfred by angle holes planned to give the attitude and true thickness of the body. In the past, drill evaluation programs fre quently used small diameter, AX (lIL' in.) or EX (,vki in.), core sizes for evaluating any deposits where shearing was minimal and where holes did not exceed 300 ft. Experience has shown, however, that large core sizes such as NX (2'a in.) or BX (ls/ in.), are preferable for better depth penetration, more geologic data, and to aid in fiber logging and dry mill ing of the core. Wire-line drill equipment and the use of non rotating core barrels are also recommended to minimize fiber loss by grinding of the core during drilling. Steps are taken to recover the sludge only where core recovery is poor, which is gen erally the case with a slip fiber occurrence. Because of the tendency of the fiber to fluff up and remain in suspension, much greater settling tank capacity is required than is the case when recovering sludge from other minerals. Care must also be taken to avoid contamination by grease and vegetable matter as these cannot be burned off without damaging the fiber. In regions where permafrost conditions are expected, every precaution should be taken to avotd-freezing the string of drill rods down the hole. The use of suitable low-freezing drill lubricant media such as a concentrated brine solution is adequate to allow drilling in areas of permafrost. However, due to the high per centage of fiber cuttings in the water return, the brine solution has to be renewed at fre quent intervals--a factor which considerably increases the cost of drilling asbestos prospects in permafrost areas. A number of successful drill ventures under permafrost conditions have been completed, including some which showed the frozen ground to persist to at least 1000 ft below surface. In areas where drilling is impractical, ex posure by trenching or exploration beneath the surface by adit or shaft and lateral workings may offer the only means of assessing a deposit. Evaluation The evaluation (Conn and Mann, 1971: Dean and Mann, 1968; Oughtred, 1952) of any asbestos deposit entails the determination of its size, as well as the grade and quality of its fiber. Dimensions of a mineral zone are estab lished by conventional methods, such as map ping, magnetic surveys, trenching, and diamond drilling. The value of the contained asbestos fiber is dependent on numerous physical prop erties such as fiber length, strength, flexibility, harshness, and color, besides (he actual amount of fiber present. The determination of grade cannot be based on a simple chemical analysis as both the fiber and the wall rock have essentially the same chemical composition. To avoid the complete crushing of the rock and physical separation of the fiber into different lengths, a method of visual evaluation has been developed which re quires careful enumeration of the total number of fiber veins, together with the average length of fiber in each vein. These fiber lengths, if expressed m sixteenths of an inch, give an ap proximation of the grade, each in. vein of fiber in a 5 - ft section being approximately 0.\ac fiber. As the price of fiber varies considerably de pending on its length, the use of grade based solely on its percentage fiber content is of little significance. Instead, the product of these two variables, expressed in dollars per ton of rock, offers a far more meaningful value which can be used for direct comparison in the final evaluation. Drill Core: The method of visual evaluation is ideally suited to the evaluation of drill core. Each vein of cross fiber is logged and the length carefully measured and recorded in mul tiples of 'in in. (Adoption of the metric sys tem based on multiples of I mm is also accept able). As veins are often of irregular width, the average width of each vein should be esti mated. Some veins are of a composite nature carrying partings, or the fiber may have kinks which cause it to break into shorter lengths. The fiber in some veins may be at right angles to the vein walls, in others sharply inclined. Allowance must be made for these conditions in arriving at the true lengths of fiber. The more precise determination of fiber con tent calls for the measurement of each vein angle in the core to permit individual volume corrections. However, in practice it is usually assumed that (he random angle is 45* and a factor of 1.414 (inverse of the sine of 45) is used. However, this can be quite misleading if the average angle is rather small, so logging results should be checked against laboratory recovery and bulk sampling wherever possible. As a rule, the visual reading gives an indi cated lower yield of a higher value fiber than a corresponding mill test. This is to be ex pected as the visual readings disregard fiber lengths of less than Ko in. which are, of course, recovered in milling and are important in grad- . 'LEGATE UMITH* Q29S*iLU IS 406 industrial Minerals and Rocks mg. Furthermore, a certain amount of pul verized host rock .idneres to the fiber, further reducing the grade and increasing the yield by 20c'c or more. On the other hand, there may be some loss of veins in the core and the veins themselves contain foreign material such as nonribrous serpentine, picrolite. and magnetite There is also a tendency, on the one hand, for some breaking of fibers to occur in the mining and nulling process while, on the other hand, ihe llulfed up milled product tends to remain on a screen which an unopened fiber would pass through. For most practical purposes, the discrepancies arc compensating and, when a suitable volume correction factor is used, the ore values found by the two methods are quite close. Slip fiber is often associated as a minor con stituent in deposits made up m.unlv of cross fiber, and in others the slip fiber may be the predominant tvpe. It is not easy to determine the slip fiber length b\ the normal visual meth ods of logging core: however, its presence mav be recorded separately by vein widths and the percentage slip fiber determined in the same manner as used for cross fiber. Laboratory assistance is almost essential m evaluating slip fibe^-deposits. Regardless of the method used in evaluating asbestos ore the final answer should give the value of the fiber, the yield and. from this, the value of the ore in Jollars per ton. A bulk sample properly milled and graded readily sup plies the answer, whereas a laboratory test normally gives only the yield ot an ungraded fiber and. therefore, of unknown value. The visual method, after due allowance for vein ancles, gives the yield only jnd further calcula tions are required in order lo approximate the fiber and ore value. [n order to place a value on the ungraded fiber resulting from laboratory extraction a graph is used (Fig. 13). The curve on this graph is derived from the Quebec Standard Tests (described elsewhere in this chapter) for average test production of all standard grades by weighting the fractions found in each box to give each grade a 'point rating." The prices for Quebec asbestos are based on a minimum shipping lest but for practical purposes the average test of production is about 20rr higher. Weighting factors for the fractions of 100 for --m.. 40 for -- -- 4 mesh. 10 for --4 -c 10 mesh, and I for --10 mesh have no real sig nificance and have been chosen only to control the shape of the curve. As an example, a fiber testing 5.7 oz on the j FIG 13--Graph ioi ewiluaiing ungraded liber Reproduced by permission of Asbestos Corp. Ltd. L m . 7 5 on the 4 mesh, and 2.3 on the 10 mesh with 0.5 in the pan would have a point rating of. 5.7 x 100 = 570 7 5 x 40 = 300 2.3 x 10 = 23 0.5 x I = -- 893 points and from the curve the fiber value would be about S455 per ton. In applying this same procedure to the visual method, it is necessary to correlate the ob served lengths with the corresponding Quebec Standard Test. In order to do so. it is assumed that fibers of '-j in. length and more will stay on the Q in. screen, ' to "fio on the 4-mesh screen, and and :liu in. on the 10-mesh, whereas the 1 i<i is assumed to end up in the pan. A synthetic Standard Test can then be arrived at by simple arithmetic. To illustrate this procedure, assume that a core length of 85 ft contains four veins of hi. length, two of ni.; in., one of "x in., two of \ m.. and one of 1 in.; 16 of Q in., three of ' i,. in., two of x in., and two of `in in.. 23 of ui. and ! 0 of in.: 74 of 1 m in. Reducing everything to a common denomi nator of 1 i.ith, there would be 104 such six teenths of G in. and over, 105 of It to `-in in.. 76 of L and li*i in., and 74 of 'in in., totaling 359 in all. 'V55ATC nurrrn l ! ( ;; raded fiber eUOJ Corp. aa the 10 ive" a point : would be 0 the visual te the obng Quebec is assumed -e will stay the 4-mesh : 10-mesh, up in the in then be ime (hat a w veins of Xi in., two three of . in.-. 23 of n denomi1 such sixi to 'An in., a., totaling Asbestos 407 In 85 ft there are 85 X 12 X 16 sixteenths; therefore, the uncorrected yield is 359 X 100 = 2 2%. 85 x 12 X 16 A correction must next be made for the av erage vein angle which will here be assumed at 45 2s Corrected yield = ---- =3 I %. sin 45 Next to arrive at the synthetic Standard Test: The fact, however, that the rock tends to break along one or more of the numerous fault planes present rather than across the fault hounded blocks to expose the veins within them, makes it difficult to obtain representa tive results. 8ulk Sampling The various methods of logging and sam pling outlined seldom give entirely dependable results. The visual methods of logging will usually produce dependable results only where ' a In. 4 Mesh 104 105 104 359 x100 105/359 x100 4 6 4.7 10 Mesh 76 76/359 x100 3.4 Pan 74 74,359 x100 33 Total 359 sixteenths 100% I6.0oz Then to find the fiber value from the graph. 4 6 x 100 = 460 4 7 x 40 = I 88 3 4 x 10 = 34 33 x I = 3 685 points From the graph the fiber value is found to be S40O-a ton. and from this the indicated ore value is calculated to be 3.1% of $400 or $ I 2.40 per ton. Face Readings On the surface or in underground workings, channel sampling may be employed. On the other hand, it is also possible to log these sur faces in a similar manner to that used for drill core. One method is to take a linear reading along either wall of a drift or crosscut and another is to take cross sections at intervals of 5 ft on the back and both walls to ensure that veins running parallel to the drive are not excluded. An alternative method is to record all the veins in the face, walls, and back after each round. In order to arrive at a percentage, a factor based on the area involved is applied to the reading for each surface, and an average percentage for the round is determined in this manner. there is a relatively low content of shorts. Slip fiber, as already noted, presents a problem in this connection. Even laboratory results which are dependent on complete extraction, usually give an appreciably higher fiber value than that obtained in a conventional mill. It is not easy to simulate in a laboratory the conditions to be found at an operating mine where the fiber from the time of blasting to the final product is subjected to a good deal of handling, some of which is rather severe. The fibers, as a consequence, suffer some breakage in the process. Bulk sampling is often resorted to as a means to check and to arrive at a suitable factor to be applied to drill core data. This may be done by diamond drilling a block of ground at close intervals prior to mining and milling. The core is then read visually and treated in the labora tory. Provided precautions are taken to avoid contamination and the sample is sufficiently large, results should be reasonably reliable despite the erratic distribution of fiber in the rock. A 12.000-ton bulk sample from one deposit indicated that a yield factor of two would be necessary to bring the "visual" ore value in line with that found by milling. In this deposit there were approximately equal amounts of slip and cross fiber and it is observed that the visual determined yield is low and the fiber value exaggerated. Fiber Value _______________________ per Ton, $___ Mill recovery laboratory recovery Visual analysis 111 164 202 ' No correction for vein angles. Yield Ore Value Correction %__________ per Ton, $______ Factor 6.80 4.59 1.87 $7.53 7,70 3.78 1.00 0.98 1.99 . LEGATE UMITF0 o e a s 'iiu is 408 Industrial Minerals and Rocks A 50,000-ton sample "assessed in the same manner also indicated a factor of two but showed that the fiber value determined visually was fairly close to that found in milling. This is attributed to the absence of slip fiber which, when present, makes the estimation of fiber value more difficult. may be prepared in this manner to correspond with expected mining level intervals, and these serve as a useful guide to mining. Separate horizontal sections contoured for rock value and fiber value per ton permit the mine op erator to produce a more balanced mill feed in respect to both fiber content and grades. Fiber Value _ ________ per Ton, $ Mill recovery Laboratory recovery Visual analysis $153 160 148 * No correction for vein angles. % 2.75 2.52 1 37 * Ore Value per Ton, $ $4.20 4.04 2.03 Yield Correction Factor 1.00 1.04 2.07 Tensile Strength In considering the preceding paragraphs, it is important to point out that the measurements made and the evaluations so obtained are based entirely on the length of the fiber which is today a secondary factor in fiber value. Most fiber grades sold today are valued for the strength they lend to cement or other mixes and a standard scale of Strength Units has been es tablished. Fibers in groups 4. 5. and 6 are sold at approximately SI.80 per Strength Unit. For example, for use in asbestos cement pipe a fiber regardless of its length distribution must test at more than 100 Strength Units and at that test will sell at approximately SI80.00 per ton. It is imperative then that any evaluation of a chrvsotile deposit include Strength Unit evalua tions which are laboratory tests involving the testing of an asbestos-cement tile made with the subject fiber. Once the inherent strength of the fiber from a particular ore body has been de termined it is usually possible to equate strength to length distribution and dust content mea surements. Tonnage and Grade To estimate the tonnage and grade of a deposit from diamond drill core data, indi vidual drill holes may be weighted according to their interval using the polygonal method. An alternative procedure is to use cross sec tions, or groups of cross sections and, by weighting the individual holes in each section, determine the average grade for each section. A third method employs contoured cross sections, wherein the contouring is based on a reasonable interpolation of the intervening area between drill holes. This method permits the estimator to make use of all available geologi cal information in his interpolation. In open pit operations contoured horizontal sections Exploitation Mining The development of asbestos mining in Can ada has been accompanied by a succession of mining practices and equipment. The simplest hand methods were, quite naturally, first em ployed in shallow open pit workings. During one period, when pits were reaching consider able depth, quite elaborate overhead cableway derricks were popular. Modern power shovels loading into heavy-duty trucks have now sup planted all other loading and transporting equipment where open cast methods are em ployed. Underground methods which have been used in the past include glory holes, shrinkage and sublevel sloping, and block caving. In some cases, scraper hoists drag the broken ore from the underground drawpoints and in others it is passed directly through grizzlies. Large primary crushers may be located under ground. The trend that prevailed in Canada, in the late 1940s and early 50s when most of asbestos was mined by underground methods, has been reversed and now open pit mining prevails. It is generally considered that surface mining is more advantageous in recovery, grade con trol, economy, and safety. The reversing of that trend is mostly due to the technological innovations in mining equipment: shovel size varies from 2`A to 15-cu-yd capacity, truck size goes from 25 to 200-ton payload, rock drilling equipment has improved considerably, and new blasting agents and techniques have been introduced. These innovations permit in creased waste to ore ratio up to 3:1 or more, thus lengthening the economic life of open pits. In Africa a large part of all the chrysotile is mined by underground methods. The ore bod- i i i f ! ST07L563 I e' no S" ms o\ is j: rm P' m. ar bi. a t re \l co wh dr or 101 Jr th, a USt jdC bas rot loa les fin BRAXEGATE LIMITFH correspond . and these . Separate rock value : mine op] mill feed ind grades. ling in Canaccession of The simplest ly, first cmigs. Dunne n% considerad cableway ewer shovels uc now supiransporting ods are emwhich have glory holes, and block iy ihe broken joints and in ugh grizzlies, icated undert m Canada. iien most of nd methods. n pit mining urface mining y. grade con: reversing of technological it shovel size xpacity. truck payload, rock | considerably, thmques have fens permit in*3:1 or more, ft of open pits, t* chrysotile is . The ore bod Asbestos 409 ies are generally tabular in shape with a pro nounced dip, with the result that the economic limit for quarry mining was reached at a com paratively early stage. Ore widths in the larger mines commonly range from 80 to 200 and up to -tOO ft. Some ore bodies, notably In the Shabani district of Rhodesia, are quite exten sive in length, in one case, development has extended for three miles along the strike, and is being developed or diamond drilled to over a thousand feet in depth. Several underground methods have been used including cut and fill. Presently, sublevel stoping and caving accounts for most of the tonnage extracted. Caving may be initiated by blasting holes drilled up ward from sublevel crosscuts, starting first on the hanging wall side and retreating over a considerable width toward the footwall, or the development and retreat may be along the strike of the ore. In some cases high pressures have developed from an arching effect but these pressures have been largely released by mining a vertical slot which may extend through to surface and toward which the ore is allowed to cave. In the sublevel stoping method a slot may also be opened across the center of the ore body. The long holes which are fanned out from the sublevel drifts are then blasted toward the slot, and mining proceeds as a systematic retreat in two directions away from the opening thus made. Drilling m the softer portions of these South African chrysotile mines is now frequently ac complished by rotary drills employing bits in which tungsten carbide cutting lugs are set. In drilling long holes, which may be up to 70 ft or more for sublevel mining, short lengths of jointed rods are used. With percussion type drills, which are generally used for harder rock than the rotary drills, flexible ribbon steel with a chisel bit of tungsten carbide has proven useful and efficient. Much of the amosite and crocidolite in Af rica has been mined from small, narrow open cuts or adits following the fiber-bearing band. In the Penge area the operations have been developed for larger scale and deeper mining. The main ironstone "reef" runs quite consist ently at around 54 in. thick with a dip of about 20. A sloping face is advanced along the strike by drilling rounds of about 6 ft with jackhammers. The broken material is shoveled back from the face into temporary pillars for roof support. The remaining material is handloaded into small cars, hoisted to a haulage level, and transported to a sorting plant for further removal of waste rock before being sent to the cobbing plant and mill. Formerly the fiber-bearing portion was hand-sorted un derground which resulted in excessive values being left behind in the pillars. The ironstone fractures into rectangular blocks which lend themselves well to being built up in this way. The main fiber-bearing reef commonly contains up to 30% asbestos, so that the proportion of waste to barren works out well for the system used. The method is locally referred to as shrinkage stopage but should not be confused because of this nomenclature with the latter system as commonly practiced in other areas. Milling Mill flow lines are designed to suit the char acteristics of a given ore body. The basic steps are similar for most flow lines. The raw fiber is recovered using the dry process which has been used almost exclusively since the incep tion of asbestos nulling in Canada some SO sears ago. However, m certain cases, wet processing of at least some of the fiber has occurred. This method of processing may be examined more closely in the future. The previous volumes of this series published in 1949 and 1960 provided a short description of some of the more commonly used equip ment peculiar to the industry. The I960 edi tion gave a brief description of the essential nulling steps. There have been few major changes m the basic process since that time. The major improvements in the past 10 years have evolved around material handling, pack aging. and shipping methods. The improved methods developed by the asbestos mining industry have made it possible for both the producer and customer to store, ship, receive, and use asbestos fiber in a relatively dust-free environment. Apart from relatively modest bulk handling systems for shorts, the major portion of the production is now being packaged in airtight woven polylaminate 100-lb pressure packed bags for export and in paper for domestic markets where fiber handling is not as severe. Both of these packaging methods can be unit ized for container and rail shipments. The trend is towards 100% mechanical handling of the asbestos product both at the mines and point of use. The flowsheet shown in Fig. 14 is a gen eralization of the essential steps and equip ment used in a Canadian chrysotile asbestos mill producing the full range of raw asbestos fiber grades Group 3 to Group 7. BRAKEfiATE UVii?n 0745632 FEOR ORE FROM MINE primary CRUSHER I [jaw OR GyRaTORy TYPE) Fig. bestos : circuit. Fig. : two-pro Fig. I lion of . iru:. and The , steps of and 11 Mill or pit . done in undergo mg open Large the mos the Can surface, quite pr particuli ing largi cause b CO cn cn OO co FIG. 15 bRAKEGATE UMi7:-n T I 5T6 -HOCADL/MP UM m3 45 0 MG G*'22L ES "OPENINGS) Ct>4 0 QTMgO YPg ( mAMM* jO5 ~AZEVAG) m c-9 :aS. 05C. DO vfcflTiCAL cls - 20 3 EOCM ST ACE EnS Only Asbestos 411 Fit!. 15 shows a section of a Canadian as bestos mill primarv rock and fiber cleaning circuit. Fig. 16 illustrates a schematic flow line of a two-product Canadian asbestos mill. Fig. 17 illustrates a recent Canadian installa tion of a primary and secondary crushing, dry ing. and ore concentration system. The description that follows of the essential steps of a milling operation is based on Figs. 14 and l 7. Mill feed is derived from the underground or pit operation. Primary crushing may be done in underground stations in the case of an underground mine or surface plant when treat ing open pit ore. Lacge jaw crushers (the 48 x 60-m. size is the most popular) are used in the majority of the Canadian plants either underground or on surface. Heavy-duty pan feeders have proven quite practical and comparatively trouble-free, particularly for handling open pit ore contain ing large unbroken pieces which are likely to cause blockages. Lately ihe trend has been towards large capacity gyratory crushers which eliminates the need for feeders and bins. In countries where relatively cheap labor is still available a certain amount of hand sorting continues to be done before or after (or both) primary crushing for the purpose of removing barren rock and also to recover pieces of the larger asbestos veins to be used in the produc tion of No. I or No. 2 crudes. Reduction in primary crushers of the size mentioned is nor mally to about 7 in., and is followed quite com monly by 7-ft or smaller cone crushers with settings ranging from 44 to 2'/i in. Ore concentration is an important step in the nulling of asbestos ore and is particularly im portant to the lower grade ore bodies. It is not uncommon to discard up to 40% of the mine ore through selective impacting and screening in the primary and secondary crushing circuits. Nearly all producers are able to accomplish heneficiation of this type to some degree. The use of magnetic pulleys is a relatively new approach being used by some producers for CUM Ml A(M t .......... MN tiM uj> rwr> rU'ry . T. . ; pU>vJE>~ P}PV4oE^SSST *NG T05 *6*5 tL - - ^, 7?1 ^ < STP745634 TAILING OlmP FIG 15--Section o/ a Canadian asbestos null shoeing the primary rock line and fiber cleaning circuit. oRAKEGATE UMITFH 412 Industrial Minerals and Rocks OM FDOM MHC FIG. 16--Schematic flow of a two-fiber- product Canadian as bestos mill. SC3S*if.UlS upgrading the mine ore. Not all asbestos ore bodies are amenable to this type of separation. The next step is to dry the ore. It is con sidered good practice to provide a storage large enough for one shift's production of mine ore to assist in regulating the flow rate to the dryers. Most of the moisture is contained in the -- I 'A in. fraction. At some plants this fraction is screened and dried separately from the over size (I 'A to 7 in.). In all stages of beneflciation it is important to minimize abrasion and cutting of the fiber particularly in the earlier stages before the longer and more easily released fiber fractions are separated from the gangue. The selection of a dryer is largely based on local preference. The two more commonly used are the rotary and vertical dryers. Re cently an installation has been made using fluid bed dryers. The chief advantage of the vertical tower and fluid bed over the rotary kiln-type dryer is normally a lesser degree of mechanical damage to the fiber. On the other hand, the rotary dryer is preferable and is also more effective for open pit ores containing snow and pieces of ice. Where conditions permit, oversize (say. +1 'A to 3 in.) material may be separated be fore drying, and bypassed to lessen the pebble milling action of rotary dryers. Where verti cal driers are used the feed should not be much coarser than a 1 'A grizzly opening size in order to avoid blockages in the gridwork of arresting bars with which the dryers are fitted. There is a limit to the air velocity which may be used in the counterflow vertical-type dryer where the products of combustion from an oil or coal-fired furnace rise through the falling ore. Near the bottom of the tower, where the hot gases enter, fluffed particles of fiber may be FIG. I *0 SCMC**T Asbestos 1SUIT0S t 0TI SCCTIW 413 Schematic iwo-fiher. nilan as- ST 07 li 5636 cil tower * dryer is al damage he rotary : effective ind pieces aze (say. anted bebe pebblesere vertit be much x in order t arresting vhich may ype dryer -om an oil Je falling where the er may be FIG. 17--Recent Canadian installation of a primary and secondary crushing, drying, and ore concentration system. BRAKEGATE 414 Industrial Minerals and Rocks temporarily held in suspension in a damaging temperature environment. One solution to this objectionable feature is to have at least pan of the hot gases introduced at the top of the tower and to be drawn down ward with the fading material. Dryers using the practical application of this principle have the discharge gas takeoff at a point midway up the height of the dryer, this keeping air velocities and temperature within permissible limits toward the bottom of the tower. An after-cooling device may also be used in which cool air is blown through the dis charged hot ore 10 remove further moisture before the ore is discharged onto conveyor belts. The air from this operation may be used as preheated makeup air in the dryers. The air and products-of-combustion as dis charged from the dryers carry a considerable volume of dust. It ts desirable, therefore, to provide filtering equipment in order to keep the plant area clean. Bag filters using various fab ric have operated successfully and are certainly the most positive means of removing the dust. Care must be exercised, however, to guard against condensation. An alternative filter which has been used is know-n-as the Impingo. This employs an everchanging layer of cold moist aggregate, or the ore itself screened to. say. --I-in. size. Some moisture is precipitated from the gases and dust adheres to the surfaces of the crushed stone or pebbles. This system has proven ineffective in most applications. It has been found desirable to have substan tial storage capacity between drying and the main stage of milling. Besides assuring an ade quate and more uniform supply of ore to the mill, further drying (up to I rc moisture loss) takes place during the storage. The size of storage facilities will vary with mill capacity. As will be apparent from the flowsheet (Fig. 14) the release and separation of fiber from gangue is accomplished by successive stages of crushing or comminution by impact. Impactors are designed to release the fiber from the host rock and at the same time produce a minimum of fines. Fiber in the form of cross-fiber veins or slip fiber thus released is at the same time suffi ciently "teased out" so that the portion so freed may be lifted by air suction, leaving most of the rock as a reject to go to the next stage of impacting and eventually to tailings. Finer fractions are generally screened out prior to air separation. Otherwise a large por tion of rock fines would be aspirated with the fiber. Rotary aspirators, designed to present a uniform layer of material to the aspirating hood are commonly used to improve the aspirating efficiency. The products of these first stages of separation may be considered as concentrates. They contain a large percentage of rock par ticles and must be further treated in the fiber grading division of the plant. Here the concentrates are further graded and undergo a scries of cleaning operations for the purpose of removing sand and dust. Screens, trommels, specific gravity air separators, and modified forms of these such as graders and dusters, further clean the fiber and separate it into standard grade lengths. In the grading mill the fiber is further sepa rated into the approximate quality brackets re quired for specific grades and is subjected to several stages of screenings using shaking screens, rotating screens, conventional trom mels, trommel-like graders, and rotary dusters. When well opened or fluffed out grades are called for. the fiber is subject to special treat ment in one or more of a variety of machines ranging from graders or Willows ( fixed shell trommels having a rotating center shaft to which beaier arms are attached) to one of several types of high-speed hammer mills, disk grinders, or pulverizers. The type of machine or machines used depends upon the length and type of fiber to be processed and the degree of opening or fluffing up required. This additional treatment is generally given to the shorter fibers. A large volume of air is used in an asbestos mill, most of which is for the primary purpose of separating fiber from rock, and dust by air suction and classification. An additional quantity is also required for dust elimination at many points within the building to keep the dust content of air in the building to a minimum. It is estimated that mills having a capacity of, say. 5000 tpd of ore. use from 500.000 to over 800,000 cfm of tree air. The average consumption in Canadian nulls is something in the order of 7 to 14 (Kula and Wiser; 1970. Rozovsky, 1957) tons of air per ton of ore treated. Modern practice requires all this air to be filtered before being discharged from the mill into the open. This has led to extensive bag filter units being installed in nearly ail mills in recent years. In Rhodesia. South Africa, and Swaziland, where there are several modern mills, one finds that (he general approach to the beneficiation ST07U5637 of . C .iii.i n. I ro I Mil ( -on dam.i In mill ' widci udepi prep., v rocn pic . s r 11 \ n grade ,'t Ti J.Tii'm 11 the c' 'rente equip; roils. ampie laiK . In Je.m, have meJ'u F." ng r.ii ion traps, on i he The ihe eo' tOs Mi to present a pirating hood 'he aspirating first stages of concentrates, of rock parI in the fiber r graded and mons for the ust. Screens, larators, and graders and irf separate it further sepabrackets resubiected to mg shaking uonal tromiary dusters, t grades are peciai treatof machines (fixed shell *r. shaft to s to one of n mills, disk of machine i length and te degree of it additional (he shorter an asbestos ary purpose dust by air equired for within the 4 air m the imated that rtpd of ore. c/m of free radian mills I (Kula and cot air per k air to be i rhe mill lensive bag ail mills in Swaziland. h one finds cneficiation Asbestos 415 of chrysotile does not differ greatly from Canadian practice. One feature of African milling is careful con trol of moisture content as this may actually tall too low. particularly during the dry sea son. Fiber may be more easily broken or damaged under extremely dry conditions. In Rhodesia the small pan crusher or Chilean mill was one in extensive use. This is no longer widely used for general nulling but has been adopted to some extent in Canada for the preparation of crudes. African practice, for the preparation of crocidolite and amosite, is generally very sim ple. consisting to a large degree in hand sorting, crushing, and screening as with the "crude" grades in Canada. However, in the Penge area of the Transvaal, milling practice is somewhat more elaborate and several milled grades of amosite are produced. In addition to the more or less conventional sornng and some very difficult cobbing due to the extreme toughness of the rock, the fiber is treated in different mill circuits variously equipped with |aw crushers, cone crushers, rolls, hammer nulls, and trommels. As an ex ample the longest grade. D . is prepared essen tially as follows: the Quebec Standard <QS.) Test. (This test is performed in the Quebec Standard Testing Ma chine which consists of a nest of three sieve boxes with m. screen. 4-mesh, and 10-mcsh screens, respectively, and a bottom box serving as a pan. A test is made with 16 oz of asbes tos and the whole mechanically shaken for 600 revolutions at 328 rpm. The equipment is made to exact standard specifications, and can be purchased through the secretary of the Quebec Asbestos Mining Assn.. 580 E. Grande Alice. Suite 320, Quebec 4. P Q., Canada.) The Que bec Asbestos Mining Assn, has set specifica tions for the various grades of fiber, showing the maximum and minimum limits tor the quantities of fiber that should remain on each screen. It is used as a production control and serves as a specification of the grade of fiber for sale. This tvpe of test has also been partially adopted bv other countries, and in some cases the results are expressed in percentages instead of ounces. Other variations of the Quebec Standard Test at some localities involve the Ro-Tapping of the Q S. fractions for further evaluating purposes, because it was believed that the Ro-Tap would give a better distribution of the fiber lengths. ) i 14 m. grizzly 1 Reduction to I Vt in. in small taw crusher i Crushing rolls (24 x 48 in.) to G m 1 Trommel -- I '/j in.--undersize to next shorter grade circuit Crushing rolls 112 x 36 in.) to '/i in 4* Trommel--Ai in. tas above I 4- Degritting trommels (2 in parallel I --1) in. X Bagging In the circuits for shorter grades, cone crush ers. hammer mills, and other fiberizing and cleaning equipment is now used. Trommels have proven effective as a cleaning device for medium as well as the long grades. For (he very short fibers high-speed vibrat ing screens are found more efficient. Air sepa ration is practiced m various forms such as air iraps. suction hoods, and screens, depending on the fiber grade being treated. Tests and Specifications The only test that is generally recognized by the government in Canada is the Quebec Asbes tos Mining Association classification known as The Ro-Tap test is used by many asbestos mill operators to obtain a fiber distribution im possible to get by the Quebec testing machine The use of the Ro-Tap differs with operators at different plants. It is not a standardized test accepted by the industry, and therefore the type and size of screens vary, as well as the lengths of time of Ro-Tapping and the quan tity of fiber used in making a test. In many cases, a cubic-foot box or a fraction of a cubic-foot box is used for obtaining the density of fibers. When the box is filled with the fiber, it is weighed and the values expressed as pounds per cubic foot. Many customers make density measurements as a guide for the introduction of the fiber in a specific product. r^ygSATE ST07U5638 416 Industrial Minerals and Rocks Wet classification and screening have been employed to an ..'.creasing extent in recent years. Equipment such as the McNctt or the Clark wet testing machine may be used for production purposes permitting the operator a much closer check on fiber lengths, nonfibrous fractions, and dust content. Many tests arc made at the special request of customers who in turn may evolve their own best methods to evaluate the fiber in terms of iheir finished products. This has resulted in tests such as: viscosity, absorption, grit, trowel ing. bulk, penetration, soluble salts, magnetite content, compressibility, flexing, tensile strength, color, strength units, surface area, and others being made. Fiber producers in other countries such as Rhodesia. Russia, Australia. The Cape and Transvaal, South Africa, have evolved their own testing methods for grading and classify ing fibers, but do use the Quebec Testing Machine to a certain degree. The classifications for various grades from the more important producing areas are given in Tables 9-1 4. Uses of Asbestos The uses ( Badollet. 1948) of asbestos fibers of all varieties are numerous and only some of the ma|or ones are listed, along with a brief discussion of the products involved. Crudes No. 1 and No. 2--Chrysotile crudes are usually processed by the customer to pro duce a long spinning fiber for use in textiles. A desirable fiber for textiles is one that has good flexibility, is soft, low in soluble salts and magnetite, and easily carded without an excess drop in shorts. It should also be free from wood and blasting wire or fuse wire. Fiber of this quality would be desirable for all textile uses, including those for the electrical industry. In some cases, this grade of fiber is used as felts in laminates along with resins to form a strong molded sheet for use in airplanes, boats, etc. Crocidolite crudes must be carefully proc essed to produce long fibers which can be used in textiles, gaskets, ropes, or in laminates with resins. Amosite crudes, after reprocessing, wilt give a long bulky fiber that is used in blanket insula tion or in products requiring a low density and good insulation value. Spinning of amosite can be accomplished, but is difficult. Croup 3 Milled Fibers--Chrysotile fibers that meet this classification are generally used in textiles. Some are used in long fiber asbes- TABLE I Ombt Gfding m Sx Fo> SPECIFICATION Group No. 1 No. I Cru<M<rott-#itMr Mint h*wng 3/4-m. nap4 *nd longar Group No. 2 No. 2 Cru<M<roM'iibor midi hv*ng 3/8-m. lupt* up (o 3/4- in Runof-Mm CrutM contittt ol un*Ortd crudot. Sundry Crud*--cental ol c/udo* other thjn tbo-m tpacified. Group No. 3 Guaranteed Minimum Snipping fast (Commonly referred to M fertile or pupping liber* 1/2 In.. 4 Me*h, 10 Me*h, P*V Ox Ox Ox Ox 3F 3K 3R 3T 32 Group No. 4 105 7 4 2 1 3.9 7 7 6 9 i 3 03 1 5 0.5 41 42 42 (Commonly referred to it nbntoi cement fiber*) 4A 40 4H 4H 4K 4M 4R 4T 42 Group No. 5 08 62 0 7.0 60 30 05 05 87 3 4 04 93 04 a4 03 94 02 10 4 0 1.5 9 5 5 (Often referred to *f peper itock gredet) 50 5K SM SR 52 Group No. 6 0 OB 10 5 5 00 12 4 00 11 5 00 10 6 00 86 7 (Paper and tfun^la fiber*) 60 Group No. 7 00 79 (Snorts and Moats) 70 7F 7M 7K 714 7R 7T 7RF and 7TF Float* 7W Grouo No. B&9 00 00 00 00 00 00 00 00 00 5 11 4 12 3 13 2 14 1 IS 0 16 0 16 0 16 0 16 (Sand* and grweltl as 8T 9T 00 0 16 Minimum 50 lb per cu fr 0o o 16 Minimum 75 lb per cu ft 00 0 16 More then 75 lb par cu ft C-1 AAA AA A AC CC AK CP AS CT AX AY CY AZ cz TABLE 10-Cassiar Asbestos Grades, Northern British Columbia Crude 3/4-tn. staple and longer. Extra long spinning fiber - Canadian Group 3 Long spinning fiber -- Canadian Group 3 Spinning fiber -- Canadian Group 3 Spinning fiber -- Canadian Group 3 Spinning fiber -- Canadian Group 3 Asbestos-cement fiber -- Canadian Group 4 Asbestos-cement fiber -- Canadian Group 4 Asbestos-cement fiber -- Canadian Group 4 Asbestos-cement fiber -- Canadian Group 4 Asbestos-cement fiber -- Canadian Group 5 Asbestos-cement fiber -- Canadian Group 5 Asbestos-cement fiber -- Canadian Group 5 Asbestoe-cement fiber -- Canadian Group 6 Asbestos-cement fiber -- Canadian Group 6 WMEGATE'*- \ ! ' edition (os :: c! u (j r risers lamin C-\ purpv not jt fullv ; Cn fibers cemer board' article 'niS. : CO --j on cn ' CO o :r sheets, cal pat gaskets Croc asbeste iioW and lo9*r. napU vO 101 3/4. i OtrdM. 5u rxlry m S^'OO'nQ ^tit 10 Mnfl, Prt, Of Oi I 3 03 t 5 05 41 42 42 60 8 7 9 8 9 '.0 95 2 3.0 3 4 3 4 4 4 s 105 ?? 11 10 86 5 4 5 6 74 79 5 11 4 12 3 13 2 14 1 15 0 16 0 16 0 16 0 IS 0 16 6 ft per cu ft 0 16 9 to par cu ft 0 16 S to par cu ft Grad#*, a r. rnadun Group 3 maddn Group 3 madtan Group 3 Mdxn Group 3 wadun Group 3 m*d*n Group 4 watfun Group 4 waptan Group 4 wadian Grouo 4 ndan Group 5 mdian Group 5 wad(*n Group 5 aoadtan Group 6 aitdian Group 6 Asbestos TABLE 11-OaaifiCJtion of African Chrysotiit* 417 C&G) Long, cnidy textile fiber C&G2 TxtiJ fiber C&G3 Long thing!# fiber C&G4 Shingle fiber C&G5 Short shingle fiber or paper stock Prom mines m the Shabam district of Rhodesia VRA-2 Textile fiber VflA-3 Long sbmgfe fiber VRA-4 Shingle fiber . From the Mashaba district of Rhodesia HVL2 Textile fiber HVL3 Long shingle fiber MVL4 Shingle fiber HVLS Short shingle or paper stock From the Havelock mme m Swaziland Msauli -- Grade 4 Shingle fibers Msauli - Grade 5 ^ From the Msauli mine near Swaziland border m the Transvaal Amianthus 1 and 2 -- Textile fibers F -- Long shingle fiber AA -- Shingle fiber From the Barberton district of the Transvaal Munmk-MyOurgh M1 -- Textile fiber iber } M3 -- Shingle fiber From tfse Barberton district near Nelsoruit of the Transvaal M4 -- Short shingle f In the absence of a current listing of Rhodesian, South African, and Swaziland grades, this list from the 1960 edition is included to indicate type and source. tos papers, packings, gaskets, brake linings, clutch facings, electrolytic diaphragms, pipe coverings, and insulating blocks. Some of the fibers of this group are now being used in laminates with resins. Crocidolite may be used for most of the purposes listed previously, providing color is not an objection. It should generally be care fully prepared in a well-opened condition. Croup 4 Milled Fibers--Many grades of fibers in this classification are used in asbestoscement processes to produce pipe, jackets, boards, sheets, and a variety of hand-molded articles. Other uses are for papers, pipe cover ings, packings, gaskets, millboards, and plastics. Crocidolite. similar to Group 4 chrysotile, is used in asbestos-cement pipes, in some packings and in some gaskets. Amosite is used in magnesia blocks, pipe coverings, and other insulation compositions when a light density is desired. It is also used in acetylene cylinders to give strength to the calcium silicate mix during curing. Group 5 Milled Fibers--Fibers of this group sometimes are used as replacements for Group 4 fibers, and therefore the products made with these fibers would include asbestos-cement sheets, corrugated or fiat boards, pipe, electri cal panels, papers, millboards, pipe coverings, gaskets, packings, brake linings, and plastics. Crocidolites of this classification are used in asbestos-cement pipes. Amosites, similar to Group 5 chrysotile al though short in length, are finding use m in sulating block of light density, such as Thermobestos or similar products, also in lightweight construction materials such as marinite board. Group 6 Milled Fibers--Chrysotile fibers of Group 6 are used in asbestos-cement shingles, flat sheets, corrugated sheets, boards, brake lining, papers, millboards, putties, and plastics. Crocidolite of this grading would be con sidered as too short in length for use in asbestos-cement products and. therefore, it would be classed as a filler and used when ever its physical properties could be employed to advantage. Amosite of this classification is considered quite short for most purposes, and would prob ably be used as a cheap filler to free up asbestos-cement slurries prior to pressing. Group 7 Milled Fibers--These fibers find usage in certain papers, cements, asphalt roof coatings, putties, paints, welding rods, floor tile, and plastics. Crocidolite and amosite fibers of a length equivalent to Group 7 chrysotile are not known to be used in commercial products unless as a cheap filler where color is not objectionable. Floats--Chrysotile floats (Badollet, 1952, 1956) are used extensively in plastics, putties, paints, welding rods, and cements. The selection of asbestos fiber for a particu lar application will depend upon the processing BRJKE6ME nM,T' ST fl 7 5 6[i 0 418 Grade 0 1 2 3 4 5 6 7 Industrial Minerals and Rocks TABLE 12--Classification of Russian Chrytotil* I Condonsad) Type Spinning fiber Spinning fiber Spinning fiber Asbestos-cement fiber Asbestos-cement fiber Paper fiber Paper and shingle Fiber and shorts Unguaranteed Texture Harsh, crudy Harsh, crudy Semi-crudy Harsh, crudy Semi-crudy Semi-open Harsh, crudy Semi-open Semi-open Open, soft Semi-open Open, soft Semi-open Open, soft Mark according to USSR Standards, 1972 DV-0 80, OV-0 55 J-1-50. J-l 38 PRJ-t-75. PRJ-1S0 J-2-20 PRJ-2-30. PRJ-2-15 P-2-30, P-2-1S J-340 P-3-70. P-3-60, P-3-50 M-3-70, M-3-60 P-4-40, P-4-30. P-4-20. P45 M-4-40. M-4-30. M-4-20. M^-5 P-5-67. P 5-65. P-5-52. P 5-50 M-5-65, M-5-50 P6-45, P-6-30 M-6-40, M-6-30 K-6-45. K-6-30, K-6-20. K-6-5 7-300 7-370 7-450 7-520 method, as well as the desired properties of the end product. The following examples outline some of the major uses for asbestos fiber and illustrate pertinent factors which influence the choice of fiber grade and type. Asbestos Cement Products--Pressure pipe which must conform to hydrostatic test speci fications is produced from high quality Group 4 fiber, usually a blend of chrysotile and crocidolite. to ensure a good modulus of rupture. On the other hand, the flexural and impact strength TABLE 13--Oasnfication of African Amosita Grade Approximate Range Average Fiber Length, In. S 11 W3 K3 SK S 33 S 33/66 GW GK S 44 RK 6605 1-1 1/2 1/2-1 1/2 1/2-1 1/2 3/16-3/4 1/8 --1/2 1/8--1/2 1/8-1/4 1/8-1/4 1/8-1/4 1/8-1/4 1/16-1/8 The grades listed above are produced in the Penge area from the Penge mine and the Weltevreden and Kromellenboog mines. The fiber lengths shown are not neces sarily exact, but have been included in order to give some indication of the relative lengths of fibers of the different grades. requirements for asbestos cement sheets can usually be met by using a Group 6 fiber. For mulations for corrugated sheets generally in clude some Group 5 material to improve ad hesion of the wet sheets during the forming process. In all asbestos cement products made by the wet machine process, drainage is an important fiber characteristic since it has direct bearing on the production rate. For this reason, pref erence may be given to fast filtering fibers and amosite may be included in the formulation as a filter aid. The requirements for shingles made by a dry process are not so exacting from either the TABLE 14--Cap* Blu* (Croddolite) Typical Values Sur Approximate Range face Area (Rigden), Grade Average Fiber Length, In. Sq Cm per G c s S 80 P 25 H H 80 713 WDS 1 1/4-1 3/4 1/4-3/4 1/4-3/4 1/4-3/4 1/8-1/2 1/8-1/2 1/8-1/2 1/8--3/8 1,500 5,500 9,500 8.300 7.500 10,000 13.000 9.000 Cape Blue Mines (Pty) Ld. produce most of the Blue asbestos. Among other producers grading practice is to refer to "long" and "short" for the bulk of their pro duction. I *l9S*l/.01S 8RAKEGATE _________ jrding to U*. 1972 55 1 SO 2 15 P-3-50 P-4-20, P-4-5 , M-4-20, M-4-5 P 5-52. P 5-50 i | i , K-6-20, K-6-5 nt sheets can 6 fiber. Forgencrally in> improve ad: the forming s made by the an important direct bearing , reason, pref-ing fibers and formulation as made by a dry om either the -0*cat Values Sur Area tRIgden). So Cm oer G 1.500 5.500 9.500 8,300 7.500 10.000 13.000 9.000 most of the Slue ling practice is to bulk of their pro- i Asbestos 419 strength or drainage point of view and can be satisfied with a lower quality 6 or 6-7 blend. Asbestos Paper--Traditionally asbestos fiber in conjunction with an organic binder has been used for the manufacture of paper and millboard which, in turn, were converted to roof ing felt, pipe coverings, electrical insulations, and many other products. Various blends of Groups 4. 5. and 6 fibers are used for this ap plication. depending upon the desired strength and porosity of the paper. More recently, a latex-asbestos process has been developed in which a long clean Group 7 fiber having a high surface area is coated with latex rubber by a chemical precipitation method and the resulting finish formed into a continu ous sheet on a paper machine. A large propor tion of this latex asbestos paper is used as an underlayment for vinyl-rolled floor covering. A lesser amount is used in the manufacture of gaskets. Friction Materials--This product line can not be related to any particular fiber group, since it spans the complete spectrum from Group 3 spinning grades to the shorter Group 7. The explanation lies in the wide variety of products, which fall within the general classi fication of "friction materials." and the equally diversified manufacturing processes involved. Clutch plates are made from an asbestos open-weave cloth impregnated with resin and bonded to a steel disk. A similar product can be manufactured by molding a dry resin-fiber blend under conditions of high temperature and pressure onto a packing plate. For the first method, a Group 3 fiber is required, whereas the molding process utilizes a Group 5. Automobile brake linings bonded to a steel shoe are usually made from Group 7 fiber in a semi-wet extrusion process while heavy blocks for railcars and large vehicles use Group 5 or 6 fiber dry-molded and machined to finished dimensions. Group 5 fiber is also used extensively in disk brake pad formulations. Sheer Packing--Latex asbestos paper made from Group 7 fiber can be densified and used for gasketing, but most sheet packing material is formed on a sheeter machine by a calender ing process. This latter method requires a longer fiber in the Group 4 to 5 range, which has been cleaned and opened. The fiber is blended with natural or synthetic rubber, plas ticizers. and other ingredients in a high shear mixer to form a dough which is later calen dered into sheets of various thicknesses. Floor Tile--A large volume of Group 7 fiber is supplied to manufacturers of vinyl floor tile. This product requires a short, clean, well opened Group 7 fiber having a high degree of uniformity in such properties as length distribu tion. absorption, and color. This latter feature is particular!'' important to the industry be cause of the need for matching of shades from different production runs. Asphalt Products--Group 7 asbestos fiber in combination with asphalt and various solvents form the basis of a wide variety of products often classified under the catchall heading of "Blacklinc." These include spray or brush-on roof coat ings. sound dcadeners for automobile body pan els. and caulking components. In recent years, automobile underbody pro tective coatings applied by airless spray equip ment have provided an outlet for Group 7 fiber. Since the finished compound must pass through an orifice 0.021 to 0.028 in. in diameter under high pressure during application to the auto mobile. the fiber used must meet strongest specifications on fineness and viscosity building properties. Short Grotip 7 chrysotile asbestos added to hot asphalt paving mix helps to improve char acteristics of toughness, flexibility, and water permeability. Asbestos modified pavements have proved successful in high traffic densitv areas, such as busy street intersections, bus stops, and bridge decks. Caulking Compounds--Combinations of long asbestos with cement and other ingredients, along with waterproofing resins, are used to produce special types of caulking compounds. In many cases, short asbestos and floats are also combined with various types of resins and other materials to produce a soft plastic caulk ing compound that remains soft or it may be controlled so as to set up as a hard mass. Plastics--Structural materials using plastics reinforced by asbestos or as a combination of asbestos and glass are now of considerable im portance commercially. The asbestos may be in the form of a mat, or as paper or cloth to form laminates with resins such as polyesters, phenolics, thermosetting silicones, melamines, and furanes. The use of long fiber chrysotile, crocidolite, and in some cases amosite, in the form of felts or papers and impregnated with resins pro duces a tough product of high strength and good heat resistance. These products have been used in aeroplane wings in England and in small sailing boats, radar scanner aerials, air craft tanks, automobile bodies, and other prod- fcRAKEGAT* ' ' 420 Industrial Minerals and Rocks ucts including rocket tubes, missile nose cones, and other parts. In some cases, asbestos in the form of cloth or a millboard type is impregnated by resins to obtain a strong sheet for structural use. Short Group 7 fiber and floats are also used extensively as a fibrous filler for the production of molded phenolic resin and polyesier parts, such as automobile heater and air conditioner housings, electric kettle basis, and other ap pliance parts. In such applications, freedom from abrasive particles is especially important to hold die wear at minimum level. Joint Filler--Another interesting use for short TABLE 15--Asbestos Prices--Canada, U.S. Standard Grade Designation Quebec, Canada IA* of Jan. 1, 1975) No. 3 Spanning fiber No. 4 Asbestos-cement fiber No. 5 Paper fiber No. 6 Paper and shingle fiber No. 7 Shorts Cassiar, Canada (As of Jan. 1. 1975) AAA Grade Nonferrous spinning fiber/Canadian Group 3 AA Grade Nonferrous spinning fiber/Canadian Grouo 3 A Grade Nonferrous spinning fiber/Canadian Group 3 AC Grade Nonferrous spinning fiber/Canadian Group 3 AK Grade Asbestos-cement fiber/Canadian Group 4 AS Grade Asbestos-cement ftber/Cjnadian Group 4 AX Grade Asbestos-cement fiber/Canadian Group 5 AY Grade Asbestos-cement fiber/Canadian Group 5 AZ Grade Asbestos-cement fiber/Canadian Group 6 Clinton Mine CP Grade Asbestos-cement fiber/Canadian Group 4 CT Grade Asbestos-cement fiber/Canadian Group 4 CY Grade Asbestos-cement fiber/Canadian Group 5 CZ Grade Asbestos-cement fiber/Canadian Group 6 Vermont (As of Sep. 1, 1974) Grades 3T and 3Z -- Fiber Grades 4A thru 4T -- Fiber Grades 50 thru 5R -- Fiber Grade 60 Waste Grades 70 thru 7T -- Shorts Grade 7TF - Floats (shorts) Grade 8S -- Shorts Hooker No. 1 - packaged in 50-fb woven poly bags Hooker No. 2 -- packaged m 100-4b woven pofy bags Arizona (A* ol Nov. 1. 19741 No. 1 Crude--soft No. 2 Crude--soft AAA Group No. 3 Nonferrous Filtering-Plastic Group No. 4 Nonferrous Filtering-Plastic Grouo No. 7 White Shorts S per Ton of 2000 Lb, F .o.b. Mine Canadian Currency 724 00-1189.00 400.00 - 614 00 255.00 -- 301.00 186.00 79.00- 152.00 F.o.b. Norm Vancouver, 9 C Canadian Currency 1560.00 1240.00 945.00 680.00 485.00 420.00 385.00 270.00 200.00 456.00 412 00 270.00 200.00 F o.b. Mornsville, Vt, U S. S 504.00- 539.00 275.00 - 466.00 198.00- 233.00 144.00 63.00- 125.00 55.00 40 00 620.00 312.00 F.o.b. Globe, Ant.. US. $ 1 750.00 1000.00 1000.00 660.00 660.00 120.00 ST0745S43 LEGATE MMiTcn polyester parts, air.conditioner and other ap,lions, freedom aally important vel. ng use for short an of 2000 b. Mine it Currency 1-1 189.00 V- 614 00 V- 301.00 186.00 V- 152.00 Xprtcouver, B.C , nCuerency 1560.00 1 240.00 945.00 680.00 485.00 420.00 385.00 270.00 20000 456.00 412.00 270.00 200.00 XHTiSVtlle, IS. $ - 539.00 - 466.00 - 233.00 144.00 _ 125.00 55.00 40.00 620.00 312.00 Globe, US.S 1 750.00 1000.00 1000.00 660.00 660.00 120.00 Asbestos TABLE 16- Annual Exports of Asbestos from Canada by Areas* United States, St Value. $ Canadian Eurooe including United Kingdom. St Value, $ Canadies South and Central America, St Value, $ Canadian Africa and Asia, St Value. $ Canadian Others. St Value. S Canadian * Figures from "Statistics Canada." 1970 614.297 71.969.000 362,711 61.536.000 25.628 5,629.000 219,480 28.096,000 340,316 60.018.000 1971 663,478 76812.000 375,261 61,868.000 22,174 4,955.000 170.697 22,160,000 323,953 58,130,000 421 1972 714,669 82,663,000 481,352 82,269,000 106,290 19,156,000 237,043 35.141.000 59 302 10,585,000 Group 7 fiber and floats is in the manufacture of joint filler cements and texture paints. Here again, fineness and whiteness are critical prop erties of the fiber. Also, since the viscosity of the mix after the addition of a prescribed amount of water must be consistent from batch to batch, the absorptive capacity of the asbestos must be controlled within very narrow limits. Canadian prices remained unchanged in 1972. Price increases by the Quebec asbestos producers for Group 7 were announced for January 1973. Cassiar Asbestos Corp. also announced increases for their grades. Prices for fibers from the major Canadian and Ameri can producing areas are listed in Table 15. Russian fiber prices vary with fiber avail ability, and only certain grades are offered for sale. The following are the approximate prices quoted in 1972, c.i.f. European ports per metric ton in Canadian dollars: P-3 5275,00 P-4 220,00 P-5 138.00 M-5 138.00 P-6 105.00 M-6 95.00 Markets Historically, the consumption of asbestos fi ber has been increasing at the rate of 3 to 4% yearly. The U S. and Western Europe have re mained the major outlets for asbestos fiber ex ports; however, in recent years, Japan and other developing countries have become a major factor in the rate of asbestos fiber con sumption. It is estimated that asbestos fiber consump tion in the U S. alone was approximately 811,000 tons in 1972. The major source of TABLE 17--Russia: Exports of Asbstos to Countries Importing Ov*r 10,000 Tpy in sny On* Y*r, 1968-1970* 1968 Million Tons Thousand Roubles Austria Belgium Bulgaria Cuba Czechosiavakia Franca E. Germany W. Germany Hungary India Italy Poland Yugoslavia Other countries Total 9.800 5,600 20,600 9,700 19,500 40,200 34.900 38,800 13,800 1,000 9,900 25,600 10,700 63,500 303,600 1,235 546 3,403 1 374 2,853 3,758 4,381 3,192 2,001 158 1,121 3,352 1,496 _ - * Figures from Roskill Information Services Ltd. 1969 Million Tons Thousand Roubles 8,500 6,300 24,600 10,600 1 7.300 42,400 39,600 22,900 14,400 18.600 8.800 28.300 14800 89,400 346800 1,097 593 4,237 1,487 2,637 3,931 4,782 2,021 2.027 2,658 1,020 3,448 2,103 _ - 1970 Million Tons Thousand Roubles 11,200 11,100 21,200 9,500 21,000 53,000 43,100 9.600 13,900 15,900 11,600 31.500 20.600 112,100 385,300 1411 1,080 3,694 1,327 3.167 4.865 5,155 1 011 1,943 2,239 1,212 3,729 2,935 - SSAKEfiATE : l'l9 S 'iL U iS 422 Industrial Minerals and Rocks * 0 | < 5 a o X "O E Q 3) < 500 n => o ^CTi ?cn ?4:<EGAT W O R LD PRODUCTION 7 3.503.720 o S > o^ UV< < ffl 6 0/61 'siw'ai pup Apw amnog Asbestos 423 supply was Canadian imports which amounted to 719.000 tons or 89% of the total require ments. On a worldwide basis, estimated consump Badollet. MS. 1937. US. Patent 2.<858.219. Jan. 19 Badollet, M.S . 1948, "Asbestos." Encyclopedia o( Chemical Technology. Vol 2. Inlerscience. New York, pp I 34-142. tion is approximately 4 million tons, of which Canada supplies 35% of world requirements. As indicated in Table 16, Western Europe ac counts for 30% or total Canadian exports. Budollet. M S., 1951, "Asbestos. A Mineral of Un paralleled Properties." Transactions. Canadian Institute of Mining & Metallurgy, Vol. 54. pp, 151-160. Budollet. MS, 1952. "Asbestos Floats.'' Trans The second largest producer is Russia, which exports over 400.000 tpy of asbestos fiber and produces over 2.2 million tons (Table 17). The ma/or end uses for asbestos fiber con actions, Canadian Institute of Mining & Metal lurgy. Vol 55. May. pp. 185-189. Budollet. MS. 1956. "The Role of Asbestos m Plastics." T ran tactions, Canadian Institute of Mining & Metallurgy. Vol. 59. pp. 283-288. tinue to be floor tile, asbestos-cement pipe and sheet, brake lining, paper products, and tex tiles. A breakdown of U.S. 1968 end use con sumption shows asbestos-cement products con Budollet. MS. 1963. "Asbestos.' Encyclopedia <>t Chemical Technology, Vol. 2. Kirk-Olhmcr. ed . Interscience. New York. pp. 734-747. Budollet. M S . and Streib, W C . 1947. U.S Patent 2.616.801. Sept 20. suming 60% of total fiber, and floor tiles 10% Budollet. M S . and Streib. W C . 1955. The Heal i Table 18). However, due to the slower increase in con sumption for asbestos-cement pipe and shinefes. the overall world growth rate will continue Treatment of Chrysolite Asbestos Fibers. ' Trans actions Canadian Institute of Mining i Metal lurgy. Vol 58. pp. 33-37 Buies R L . 1969. "Metjmorphic Minerals--Ashestos." The Geology of Industrial Rocks and W<u- to be 2 to 3 % > early. era/s. Dover Publications. New York, pp 317328. Health Hazards Bates, f F . et al . 1950. "Tubular Crvslals of Chrvsotile Asbestos." icie/itv. Vol. 3, pp 512- In the area of health hazards, the asbestos industry has taken measures to answer state ments on the usage and safe application of asbestos by setting up the Asbestos information 513. Bear. L.M . 1963. "The Mineral Resources and Mining Industry of Cyprus." Bulletin No I. Geological Survey. Cyprus. 208 pp. Berger. H. 1963. Asbestos Fundamentals. Chemi A^-sn. North America, whose basic objectives cal Publishing Co . New York. 17! pp. are to: (1) provide an authoritative channel of communication, (2) rebut irresponsible statements. (3) disseminate information on the uses of asbestos in our modern technological Bourussu. PJ.. 1957. The Asbestos Mine of Nicolet Asbestos Mines Limited." The Geologs ni Canadian industrial Mineral Deposits, 6lh Com monwealth Mining and Metallurgical Cuncrcss. pp. 26-27. society. Bowles. O. 1955. "The Asbestos Industry. ' Bulle tin 552. U.S. Bureau of Mines. 122 pp. Bibliography and References Bragg. W L.. 1937. "The Pyroxene and Amphibole Groups." Atomic Structure of Minerals, Unn Anon.. 1966. 7'esttng Procedures for Chr\sonic Cornel! Press, p 184. Asbestos Fiber. 2nd ed.. Quebec Asbestos Min Brindley, GAV.. and Zussman. J., 1957, "A Struc- ing Assn. iur.il Study of the Thermal Transformation of Anon. 1972. Geological Guide to the AsbestosRegion of Southeast Quebec. Quebec Serpentine Minerals to Forsteruc." American \fmeraiogist, Vol. 42. No. 7-8. pp. 461-474 1 Asbestos .Mining Assn., p. 32 Allen. C C.. Gill. J C.. and Koski. J S . 1957. The Curroll-Porczvnski. C.Z.. 1956. Asbestos, The Textile Institute. Manchester. England Jeffrey Mine of Canadian Johns-Manv ille Com pany. Limited,'* The Gcologs of Canadian In dustrial \tineraI Deposits. 6th Commonwealth Mining and Metallurgical Congress, pp. 27-36. Anderson. H.V . and Clark. G L,. J929. 'Applica tion of X-Rays m the Classification of Fibrous Silicate Minerals Commonly Termed Asbestos.' Industrial A Engineering Chemistry No. 10. pp. 924-933 Aruja. E.. 1944. "Displacement of X-Rav Reflec Chidester. A H . and Shnde. A.F . 1962. "Asbestos in the U.S.. Exclusive of Alaska and Hawaii." Mineral Investigation Research Slap MP 17. U S Geological Survey. Cilliers. File R.. 1964, "Amosite at the Pence Asbestos Mine." Vol. 2. The Geology of Some Ore Deposits of Southern Africa. Geological So ciety of South Africa, pp. 579-59!. Cilliers. J J le R . and Gems, J H.. 1964. "Crocido- ) tions." Xatnre. Vol. 154. p 53 Aruia. E. 1944a. "An X-Ray Study of the Crvstul hte Asbestos in the Cape Province." The Geol ogs ol Some Ore Deposits of Southern Africa, Structure of Amigorite." Mineraiogical Maga- Vol 2. The Geological Society of South Africa, :me. Vol 27. pp. 65-74 pp 543-570 A\erv. R B . Conant. M.L.. and Weissenborn. H F . Cilliers. if te R.. el al,. 1961. "Crocidohle from 1958. Selected Annotated Bibliography of As the Koegas-Westerberg Area. South Africa." bestos Resources m the United States and Can Economic Geology, Vol. 56, pp. 1421-1437 ada.'* Bulletin 1019-L. US. Geological Survey, Conn. H M K , 1967. "Geophysics and Asbestos pp. 817-865. Exploration." V/iMiVr? and Groundwater Gen- 9'195*1 a m LEGATE HMiTcn 424 Industrial Minerals and Rocks phvsics. Economic Geology Report No. 26. Geo logic Survey of Canada, pp. 485-491 Conn. H.K . and Mann. E L.. 1971. "Evaluation of Asbestos Deposits." SME Preprint No. 7I-H-27. AIME Annual Meeting. New York. 9 pp Cooke. H.C.. 1937. "THelford. Disraeli and East ern Half of Warwick Map Areas. Quebec." Memoir 211. Geological Survey of Canada, pp. 86--140. Dean. A.W.. and Mann. E l... 1968. "The Evalua tion of Chrysotile Asbestos Deposits." Ore Re<ene Estimation anti Grade Control. Special Vol. 9. Canadian Institute of Mining Sc Metal lurgy. pp.281-286 Douglas. R.J.W. 1970. Geology and Economic Minerals of Canada. Economic Geology Re port No. 1. Geological Survey of Canada. Dept, of Energy. Mines and Resources. 838 pp. duToit. A.L.. 1946. "The Origin of the Amphibole Asbestos Deposits of South Africa." Transac tions. Geological Society of South Africa. Vol. 48. pp. 161-206. Fankuchen. I., and Schneider. M.. 1944. "Low Angle X-Ray Scattering from Chrysolites." Jour nal of .4 uterican Chemical Society. Vol. 66. No 3. Mar. pp 500-501. Frankel. IJ., 1953. "South African Asbestos Fi bres." Mining Magazine. London. Nos. 2 and 3. pp 89.73-83: 142-149 Genis. J.H.. 1964, "The Formation of Crocidolite Asbestos," The Geology of Some Ore Deposits in Southern Africa. Vol. 2. Geological Society of South Africa, pp. 571-578. Gold, D P . 1967. "Local Deformation Structures in a Serpentinite." Ultramafic and Related Rocks. P.J Wyllie. ed.. John Wiley. New York. pp 200-202. Graham. R.P.D. 1944. "Serpentine Belt. Eastern Townships." Geology of Quebec, Geology Re port 20. Dept, of Mines, Quebec. Vol. 2. pp. 439-443 Hall. A.L.. 1930. Asbestos in the Union of South Africa. Memoir 12. 2nd ed.. Geological Survey of South Africa, p. 324. Hendry. N.W., 1972. "The Outlook for Asbestos in Canada." Bulletin, Canadian Institute of Min ing Sc Metallurgy, Vol. 65. No. 724, Aug., pp. 40-44. Hendry, NW. and Conn, H.K., 1957. "The On tario Asbestos Properties of Canadian JohnsManville Company, Limited." The Geology of Canadian Industrial Mineral Deposits. 6th Com monwealth Mining and Metallurgical Congress, pp. 36-44. Hillier. ) . and Turkevich. J.. 1949. "Electron Microscopy of Colloidal Systems." Analytical Chemistry. Vol. 21, No. 4. Apr., pp. 475-485. Hodgson, A.A., 1965, "Fibrous Silicates," Lecture Series No. 4. Royal Institute of Chemistry. Keep, F E,, 1961, "Amphibole Asbestos in the Union of South Africa." Transactions. 7th Com monwealth Mining and Metallurgical Congress. Vol. I. pp. 90-120. Keith. S B., and Bain, G.W. 1932. "Chrysotile Asbestos: 1 Chrysotile Veins." Economic Ge ology. Vol. 27. pp. 169-188. Kula, j . and Wiser. J.P.. 1970. "Msauli Asbestos Mill." World Mining. Sep., pp. 26-29. Lamarche. R.Y.. 1972. "Ophiolites of Southern Quebec," Canadian Contributions l-l I to the Gcodsnamics Project--A Symposium, Earth Physical Branch, Dept, of Energy, Mines and Resources. Ottawa. Laubscher. D.H., 1964, "The Occurrence and Ori gin of Chrysotile Asbestos and Associated Rocks. Shabani. Southern Rhodesia." The Ge ology of Some Ore Deposits of Southern Africa. Vol 2. The Geological Society of South Africa pp. 593-624. ------- ----- - -- * - yjs-i. a itv vt i^iii untj L/kkUl' rence of Chrysotile Asbestos in the Shabani and Mashaba Areas. Rhodesia." Symposium on Rho desian Basement Complex. Transactions Geo logical Society of South Africa Annexure Vol 71. pp. 195-204. Leney. G.W . and Loeb. E.E.. 1972, "The Geology and Mining Operations at Pacific Asbestos Cor poration." Asbestos, Vol. 54. No. 4. pp, 4-14, Low. I H.. 1951. "Magnetic Prospecting Methods m Asbestos Exploration." Transactions. Cana dian Institute of Mining Sc Metallurgy Vol '4 pp 388-395. Mamen. C.. ed.. 1973. "China's Mineral Industry," C21a-n3a1d.ian Mining Journal. Vol 94. N o I . vdvo May T C.. and Lewis. R.W.. 1970. "Asbestos." Mineral Facts and Problems. Bulletin 650. U S. Bureau of Mines, pp. 851-863 Merrill, R.J., 1957, "The Carey-Canadian Asbestos Deposit." The Geology of Canadian Industrial Mineral Deposits. 6th Commonwealth Mining and Metallurgical Congress, pp. 45--49. Miles, K.R., 1942, "The Blue Asbestos-Bearing Banded Iron Formations of the Hammersley Range. Western Australia." Bulletin No. 100. Geological Survey of Western Australia Pt 1 pp. 5-37. Munro. R.C., and Reim, K.M.. 1962. "Coalinga Asbestos Fiber--A Newcomer to the Asbestos Industry." Canadian Mining Journal, Vol. 83, No. 8. Aug.: Mining Engineering, Vol. 14 No 9. pp 60-62. Nalivkin. D.V.. 1960, The Geology of the U SS R. --A Short Outline, trans. by S.l. Tomkeiff. J E. Richey, trans. ed.. Pergamon Press. 170 pp. Oldham. J.W.. 1968. "A Short Note on the Recent Geological Mapping of the Shabani Area," Sym posium on Thodesian Basement Complex. Trans actions. Geological Society of South Africa An nexure, Vol. 71. pp. 189-194. Pauling, L,, 1930. "The Structure of the Chlorites," Proceedings, National Academy of Science, Vol. 16, p. 578. Pelletier, R.A.. 1964, Mineral Resources of SouthCentral Africa, Oxford University Press. 277 pp. Pundsack, F.L.. 1955, The Properties of Asbestos. I. The Colloidal and Surface Chemistry of Chrysotile. Journal of Physical Chemistry Vol 59, No. 9. Sep , pp. 892-895. Pundsack, F L,, 1956. "The Properties of Asbestos. II. The Density and Structure of Chysotiie." Journal of Physical Chemistry. Vol. 60. No. 3. Mar., pp. 361-364. Pundsack. F.L.. and Reimschussel. G.. 1956, "The Properties of Asbestos. III. Basicity of Chysotiie Suspensions," Journal of Physical Chemistry, Vol. 60. Sep , pp. 1218-1222. Rabbit, J.C.. 1948. "A New Study of the Anthophyllite Series." American Mineralogist, Vol 33, May-June, pp. 263-323. ST07456U fcRAKEGVTE 1 ;y. Mines and rcnce and Oriid Associated su." The Geutl.ern Africa. South Africa. n and Occure Shabani and mum on Rhoacnons. Geonnesure, Vol. "The Geology Asbestos Cor- 4. pp 4-14 ting Methods aiota. Canaizgy. Vol. 54. ral Industry." *. No. I. pp. . "Asbestos." sin 650. US. ban Asbestos *n Industrial eallh Mining 49 estys-Bearing H-mmersley m No. 100. tralia. Pt. I. 2, "Coalinga the Asbestos /. Vol. 83. Vol. 14. No. the U S S R. aaikciff. J.E. 170 pp. the Recent Area." Symiplex. Transi Africa An- e Chlorites." oence. Vol. es of Southess. 277 pp. af Asbestos, icmtstry of matey, Vol. of Asbestos. Oysotile." 60. No 3. 1966. "The rf Chysotile t Asbestos 425 Rice. SJ.. 1963. "California Asbestos Industry," Mineral Information Service. California Div. of Mines. Vol. 16. No. 9. pp. 4-6. Riordan. P.H., 1952. "Geology of the Thetford- Black Lake District of Quebec with Particular Reference to the Asbestos Deposits." Ph.D. Thesis. McGill University, unpublished. Riordon. P H.. 1955. "The Genesis of Asbestos in L ltrabasic Rocks." Economic Geology, Vol. 50. No 1. pp. 67-81. Riordon. P.H.. 1957. "The Structural Environment of the Thetford-Black Lake Asbestos Deposits." Proceedings. Geological Assn of Canada. Vol. 9. pp. 83-93. Riordon. P H.. 1957a. "The Asbestos Belt of South eastern Quebec." The Geology of Canadian In dustrial Mineral Deposits. 6th Commonwealth Mining and Metallurgical Congress, pp. 3-8. Riordon. PH.. 1957b. "The Asbestos Deposits of Thetford Mines. Quebec." The Geologs of Canathan Industrial Mineral Deposits. 6th Common wealth Mining and Metallurgical Congress, pp. 9-17 Riordan. PH.. 1957c. "The British Canadian Mine." The Geology ot Canadian Industrial Mineral Deposits. 6th Commonwealth Mining and Metallurgical Congress, pp. 17-21. Riordon. P.H.. I957d. "Normandie and Vimy Ridge Mines." The Geology of Canadian Indus trial Mineral Deposits. 6th Commonwealth Min ing and Metallurgical Congress, pp. 21-26. Riordon. P H.. and Laliberte. R.. 1957. "Asbestos Deposits of Southern Quebec." Excursion B-OS Gjudebook. 24th International Geological Con gress. Canada, pp. 1-21. Robinson. K.. and Shaw. E.R S . 1952. "Summa rized Proceeding of a Conference on Structures of Silicate Minerals (November 1951)." British Journal ot Applied Physics. Vol. 3. Sept., pp. 277-282. Rosato. D.V . 1959. Asbestos. Its Industrial Appli cations, Reinhold. New York, pp 198-199. Rowbotham. P.I.. ed.. 1970. "World Asbestos In dustry." Industrial Minerals, No. 28. Jan., pp. 17-29. Rozovsky. H., 1957. "Air in Asbestos Milling," Ventilating Conference, Keller Center for Con tinuing Education. Michigan State University. Smirnov. V I.. 1971. Essays on Melatlogeny. trans by E.A. Alexandrov. Queens College Press, 96 PP Smithenngale. W.V.. 1957, "The Mine of Cassiar Asbestos Corporation Limited. Cassiar. B.C.," The Geology ot Canadian Industrial Mineral Deposits, 6th Commonwealth Mining and Metal lurgical Congress, pp. 49-53. Speil, S.S.. and Leineweber, J.P., 1969. "Asbestos Minerals in Modern Technology," Environ mental Research, Vol. 2. No. 3. Apr . pp. 166208 St-lulien, P . 1967, "Tectonics of Part of the Appa lachian Region of Southeastern Quebec." Special Publication 10. Royal Society of Canada, pp. 41 --47. Straw. D J . 1955. "A World Survey of the Main Chrysotile Asbestos Deposits." Canadian Mining ct Metallurgical Bulletin. Vol. 48. pp. 610-630. Van Biljon. W J . 1964. "The Chrysotile Deposits of (he Eastern Transvaal and Swaziland." Geol ogy of Some Ore Deposits in Southern Africa. Vol. 2. Geological Society of South Africa, pp 625-669 Vokes. FM. 1964. "Asbestos Bearing Claims on Troodos." U S. Special Fund Protect. Cyprus. United Nations unpublished Report. Warren. B E.. 1932. "Structure of Asbestos--An X-Ray Study." Industrial Engineering Cltettiistrr, Vol 24. No. 4. pp. 419-422. Warren. B E . 1942. "X-Ray Study of Chrysotile Asbestos." American Mineralogist. No 27. p 235. Warren. B E . and Bragg. W L.. 1928. "The Struc ture of Diopside." Zeitschnft juer Krist. Vol 69. pp. 168-193. Warren. B E.. and Hering. K.W . 1941. "The Ran dom Structure of Chrysotile Asbestos." Physical Reviews. No. 59. p. 925. Whittaker. E.J.W.. 1952. "The Unit Cell of Chysotile." Acta Cltrvstalogica. Vol. 5. pp. 143-144. Whittaker. E.J.W.. and Zussman. j.. 1956. "The Characterization of Serpentine Minerals by X-Ray Diffraction." Mineralogical Magazine. MO. 31. pp. 107-126. Wilson. J.F.. 1968. "The Mashaba Igneous Com plex and Its Subsequent Deformation." Sympo sium on Rhodesian Basement Complex. Geolog ical Society of South Africa Annexure. Vol. 71. pp. 175-188. Yada. K.. 1967. "Study of Chrysotile Asbestos by a High Resolution Microscope." Acta Chrvstalogica. Vol. 23. pp. 704-710. Yada. K. 1971. "Study of Microstructure of Chrysotile Asbestos by High Resolution Electron Microscopy." Acta Chrvstalogtca. Vol. A27. pp. 659-664 Zussman. J.. Brindley, G.W.. and Comer. J J.. 1957. "Electron Diffraction Studies of Serpentine Minerals." American Mineralogist. No. 42. pp 1 33-1 53. ST0745648