Document 2qG5aZgxNxMM7QabvwqNj51wp

Comments on the proposed method of identifying chrysotile and amphibole in talc to be used in foods and drugs that are to be taken internally as described in the Federal Register, Food and Drug Administration, Vol. 38, No. 188, September 28, 1973, Section 121.2006C, pages 27079 27081. Malcolm Ross Geochemist U.S. Geological Survey Washington, D.C. 20244 The optical method proposed in Section 121.2006C may not be sufficient to identify small amounts of asbestos (amphiboles and chrysotile) in many commercial talcs. The optical method is good for screening samples for further work utilizing X-ray and electron diffraction and electron microscopy. It is attractive to propose the optical microscope as a general analytical tool as many laboratories have this instrument but do not have more sophisticated analytical equipment. However, the optical method is not easy to use for the identification of very small asbestos fibers when they are present in a matrix of finely milled talc-- which often itself takes on a fibrous appearance. If the asbestos contaminants are the typically long chrysotile fibers (10-10,000 microns) such as those from the Quebec, Canada localities their detection would be quite easy by the optical method-- subject to verification by a diffraction technique or by semi-quantitative chemical analysis by electron probe or energy dispersive methods. Talc may be contaminated with any of the following minerals : (1) varieties of amphibole including tremolite, actinolite, cummingtonite, grunerite=amosite, and anthopyhllite, (2) calcium-magnesium carbonates (calcite and dolomite), (3) chlorite, (4) sericite=mica, (5) quartz, and (6) serpentine which includes the varieties antigorite, lizardite, and chrysotile. Only the amphiboles and serpentines need concern us here.  <* Antigorite and lizaride are platey in habit-- just like talc in their overall morphology. Chemically these two minerals are also very similar to talc-- a health hazard has not been demonstrated for antigorite and lizardite. Chrysotile is chemically and structurally very similar to antigorite and lizardite. The difference is in the morphology for due to the structural mismatch of the octahedral and tetrahedral positions of the Mg3Si205(OH)4 layers in chrysotile the layers roll up to form tubes. Many of the optical properties and the X-ray diffraction powder patterns of chrysotile are identical to those of antigorite and lizardite. Talc mines contain a complex assemblage of minerals. Locally, essentially pure talc may be mined but more typically the talc ore will change tenor from one part of the mine to another. For example, in the Arnold open pit at the Gouverneur, New York talc locality, the mineral assemblage changes drastically every few feet or every few inches across the floor of the pit. For a description of the mineral assemblages found in the Arnold pit, see M. Ross, W.L. Smith, and W.H. Ashton, American Mineralogist, Vol. 53, 1968, p. 751-769. Talc and the associated primary silicates may be in the process of altering intragranularly to other minerals. For example, talc platelets may be recrystallizing to a form of serpentine and tremolite may be altering to fibrous anthophyllite. Such alterations are often on the micron or sub-micron scale. The ultramafic talc deposits of Vermont show similar complex changes of mineral assemblages. The core of the ultramafic bodies is often a serpentine rock which grades outward into 2 talc-serpentine-carbonate rock, then steatite (massive talc ore containing often small amounts of serpentine), then blackwall rock (amphiboles, quartz, albite, etc.), and finally the country rock. From this discussion it can be seen that talc ore can present great difficulties to the analyst-particularly after it has been milled. If asbestos is present in the talc ore, it may be in a form that will be very hard to characterize. The asbestos fibers may be much less than 5 microns long and may perhaps be imbedded within the talc platelet. It also may be very difficult to tell whether this type of material is antigorite, lizardite, or chrysotile. As mentioned above, the milling of talc may shear the talc platelets so that they take on a fibrous appearance. In cosmetic talc samples at my disposal the talc fibers are typically 0.1 to 10 microns long. These talc fibers closely resemble fibrous serpentine (chrysotile) and to distinguish between them by the measurement of the indicies of refraction requires a highly competent microscopist and also one with great patience and untiring eyes. In section 121.2006C a limit of 100 chrysolite fibers and 1000 amphibole fibers per milligram of talc product is proposed. I estimate that the average size of a talc platelet in a commercial milled talc product is 10x10x2 microns in size. A great many particles are much smaller than this. A one milligram sample of this talc (specific gravity = 2.6 g/cm^) would contain two million or more particles. Consider the problem of looking for 100 tiny chrysotile fibers in 2,000,000 talc particles (one in 20,000) . I seriously doubt if this can be done unless the asbestos occurs in fibers greater than 10 microns long. Also, are asbestos fibers less than 5 microns long not a health hazard? 3 The generally coarse grained prismatic primary amphiboles found in talc ores can usually be identified with some confidence by optical methods. Problems with this method may be encountered if the amphibole is altering to some fibrous form of asbestos (tremolite -- > anthophyllite, anthophyllite -- > chrysotile). In order to properly characterize talc products, I would recommend the following procedure : (1) Optical screening as proposed in section 121.2006C to identify coarse grained primary amphiboles and chrysotile if present as fibers 10 or more microns long. Optical methods alone will not always suffice to tell just what variety of amphibole is present. (2) If the asbestos contaminant is present in amounts greater than one weight percent (well above the limits set in section 121.2006C), X-ray powder diffraction methods can be used to identify amphibole and serpentine. It would be very difficult to identify the type of amphibole or serpentine present by the X-ray powder method unless they were present in very large amounts (10 weight percent or more). All three serpentines, o antigorite, lizardite, and chrysotile show a 7.4 A powder line. The o appearance of this 7.4 A line has been used by some to prove the presence of chrysotile. This is not correct for the plately serpentines have this same powder line. (3) If the talc sample contains very fine asbestos particles (<10 microns), electron microscopy (transmission and/or scanning), electron diffraction, and energy dispersive semi-quantitive chemical analysis should be used to make absolute mineralogical identification. If the electron micrographs show the typical "rolled up tubes" it is a fairly 4 . 14 good identification for chrysotile. If the particles are all plately they could be talc, chlorite, mica, antigorite, or lizardite. The electron diffraction patterns of these five minerals are very similar (hexagonal array of spots) but are quite different from the electron diffraction pattern of chrysotile. The amphiboles can be characterized, although not without some difficulty, by using electron diffraction and energy dispersive semi-quantitative chemical analysis. If there is intragranular alteration of the talc plates or amphibole prisms phase identification may be quite difficult. 5 THE AMERICAN' MINERALOGIST, VOL 5,i, MAY JUNE, 1968 TRICLINIC TALC AND ASSOCIATED AMPHIBOLES FROM GOUVERNEUR MINING DISTRICT, NEW YORK1 M alcolm William L. RSmositsh, ,UB. aSt.teGlleeoMloegmicaolriSaulrIvnesyt,ituWtea,shCinoglutomnb,uDs,. OCh.io2042342203 AND William H. A shton, Johnson and Johnson, New Brunswick, New Jersey 08903. Abstract New chemical, optical, and X-ray data are given for talc, tremolite, and a manganoan amphibole (tirodite) from the Gouverneur mining district, New York. All talc examined is found group to Cl be or triclinic, C l, struc a = 5.255, ture type 6 --9.13,, c= 9.44s A, a 1-layer triclinic (ITc ) = 9046', Chemical d --98'5 analysis 5g',iv7es=th9e0c0o',msppoascie tion of talc from the Arnold pit as Mg9oiSis %OioIo io(OH)i On the basis of fluorine analyses of 22 talcs from worldwide localities it is observed that talc derived from meta morphosed sedimentary rocks contains appreciable fluorine, from 0 11 to 0.48 weight per cent, whereas talc derived from ultramafic rocks contains less fluorine. Two of the three tremolite specimens examined have prominent lamellae, oriented parallel to (10T), of a second amphibole having the following unit-cell parameters: mono clinic, a = 9.50, 6 = 18.04, c= 5.28 , (3= 10225', space group P2i or P 2Jm . Chemical and X-ray evidence indicates that this amphibole is tirodite having the approximate composi tion Ca0.M n0 9Mg5 gSisCfelOH.FL The tirodite probably exsolved from the host tremo lite at temperatures below 500C. New unit-cell data are given from three tremolites. X-ray powder data are given foi talc and tremolite. I ntroduction The purpose of this paper is to present new chemical, X-ray, and opti cal data for talc and the associated amphiboles tremolite and tirodite fTdouhucinstidnstgiunodcnyetrihtsaeipnpahrstycshoiifcsatasl bafrrnoodmadchethereminiGcvaoelustpvirgeoranptieeourntriemws hionifcinhtagltchdeiasntarduictthth,oeNraseswsaorecYicaootreknd. minerals lying in the system Ca0-M g0-Sj02-H20 -C 0 2. The metamor phosed sedimentary rocks of the New York Grenville Lowlands are ideal for such a study for many ot the mineral compositions lie mostly within this system. The present paper will present data only for the talc-tremolpirteopsecrhtiiestss ooff tthaelcGaonudvetrrnemeuorliatreeaw. eArelthtohuoguhghtthetochbeemiwcaelll aknndopwhny,siocuarl s(1tu9d6v6) asnhdowthteharet cmenutchstuisdiyeest otfo Bboewdnon(e19i6n6)oradnedr tRo afyunlleyr cahnadracBtreorwizne these phases. 'S tudies of silicate minerals (10). Publication authorized by the Director, U. S. Geo logical Survey. 751 752 .1/ ILLUI.M RUSS, It I L L ! . 1.1/ L S M I T H A M ) W I L L I A M II ASHTON T he Gouverneur Mining D istrict vilTleheLoGwoluavnedrsneoufr,thoer Bnaolrmthawt-eEstdwAadridrso,ndmaicnkins,g Sdti.strLicatwrisenincethCe'oGunretvn, Xew York. Most of the bedrock of the Gouverneur area consists of meta sedimentary and metasomatic rocks referred to as the Precambrian Grenville Series. The talc containing schists are found in a northeast trending belt which was described by Engel (1962) as more than six mingilesdolownng,ddipippsionmgeap2p,5r0o0xifmeeatt,elayn4d5atttoaitnhiengnoarthmwaexsitmpurmobathbilcykenxetsesndof ghirgehaltyerfothldaend 4a0n0d fseheet.arTedhemtaalrcbleboodfietsheocGcurernvasillseheSeetrsiesa.nd lenses in a Metamorphic reactions between quartzite and dolomite produced various magnesium- and calcium-bearing silicates, especially diopside, tremolite, anthoph_\ llite, and talc. Some of the talc and anthophvllite and probabh all the serpentine formed by later alteration of tremolite. oSfomtreemofotlhitee stcohiastms oarree cmalacgintiecs,iupmrobraicbhlypahsasaeb. y-product in the alteration The amounts of the various minerals differ throughout the area; however, the predominant mineral is usually tremolite. In addition to the pyroxene, amphibole, talc, and serpentine constituents of the ores, there are also varying amounts of quartz, carbonates, gypsum, chlorite, aanndd athcceeyssvoaryn'mininceoralolsr. fTroemxtubruaflflyanthdegtraalycstoranwgheitfer.om massive to platv, Occurrence The Arnold pit of the International Talc Company, near Fowler, was vinistihteids sintu1d9y61waenred aogbataininiendOfcrotombetrh,is19p6i6t.. .Many of the samples described of Tahegleaxcpiaotseedd sruocrfkacaet twhehiAchrnwoladspbite,inngeacrltehaereodldoAf rsnooill,d asnhdafti,nctoonwsihsticehd etoxcbaevafrtoiomnsabwoeuret 2b8e0intgo movaedre.30T0hefeewtidinththoef athreeaesxapmopsulerde.wTahseessetiqmueantecde of rock types from the footwall dolomite to the hanging wall dolomite was observed to be as follows, as traversed across the floor of the mine in a westerly to northwesterly direction:12345 (1) footwall dolomite (2) "limy talc" rock, about 30 feet (G-16) (3) "coarsely crystalline talc" lens, about 5 feet (G-17) (4) massive "talc ore," about 115 feet (G-18) (5) a sequence of an irregular interbedding of coarselv crvstalline TRICLINIC TALC FROM GOl'VTRNFUR 753 tremolite (varietv hexagonite) and massive taic ore, about 130 to 150 fee(t6)(Gh-a1n9g, i2n0g, w21a,ll2d2o) lomite. The occurrence of a lens of coarsely crystalline talc near the footwall cwraysstaatlylipniecatlalocf atnhde tehxepohseexdagroocnkit.eT-bheearcinomg prolecxk iwntaesrbperdodnionugncoefdcotoawrsaerldy the hanging wall. The exposures of this type of talc ranged from a few nitnaalcnchtelwyshtitocahlcawfweewritehfceoaeltlsemicntaelwdl iafdomtrhom.uTinntheeroafslopcgeleiccaiamrleusnntsualdotyefretwhdeertecreofmoaruosneldiltyet.ocTrbyhesetdaolrlemilnaie tively coarse grained talc, known as "scale" at the mines, is associated with but distinctly different from the fine-grained commercial talc. fouArthsimlevilealrocfotahreseWlyigchrtymstainlleinoef tthaelcInwtearsnantoiotendalinTaMlc aCyo, m1p9a6n1,y,ownhtihche fisorlomcaattieodn.abTohuet m3,a0t0e0rifaeleftrotomththeissopuathrtwoefstthoef tmhieneArisnorilcdhpeiit,inintrtehme oslaimtee; the translucent to pure white talc and clear colorless tremolite being the major phases. Minor fibrous anthophv llite, partly altered to talc, is also present as a minor constituent. The sheetlike body of tremolite-coarsely lie. 1 Inde\ map of the Gouverneur talc mining areas, St Lawrence Count), New York Modified, in part, from Engel, 1962, Plate I. 754 MALCOLM ROSS, WILLIAM L. SMITH AND WILLIAM II. ASHTON crystalline talc rock was about 12 feet thick where examined and was reported to extend more or less continuously along the strike of the ore. The body extends from sixth level of the mine. the surface 01 near the surface down through the Additional samples of well crystallized talc obtained previously from the Arnold pit (G-l), and the "Talc" mine (CS-1), Gouverneur, N.Y., and also a sample of nearly pure quartz-tremolite rock from an area 3 '4 of a mile southwest of the Wight mine (G-24) were also studied. The location of the various mines is given in the index map (Figure 1). The apparent mineral associations of the more carefully studied sam ples are as follows: (1) G-l, talc-minor clear tremolite and anthophyllite (2) G-16, clear tremolite-serpentine-talc-minor carbonate and tirodite (3) G -l7, talc-minor clear tremolite (4) G -l9, 21, lavender tremolite (hexagonite)-minor quartz, carbo nate, tirodite, and tourmaline (5) G-24, tremolite-quartz-minor tirodite Small amounts of carbonate appear as a cementing agent in samples G-16 and G-21. On the basis of a rapid reaction to dilute HC1 the cementing carbonate is probably calcite. T alc Chemical composition.--The coarsely crystalline talcs (G-l, G-17) taken fcrroymstatlhseofAtrrneomldolpitiet ainpp1e9a6r1oanncdar1e9f6u6l oarpeticnaelarelxyampuirnea,tioonnlyofathfeewpiscmkaeldl pmeartceerniatl.caTlchirueme stpheucstrothgerapahmicouanntaloyfseisnc(lTudaebdle tr1e)msohloiwte liesssnethglaingib0l.e2. Wet chemical analysis (Table 2) confirms the presence of fluorine in the talc structure. Total loss (HoO+F) on ignition for samples G-l and G-17 are given in Table 3. The chemical formula of this talc as given by the analysis G-l is: Alg3.04Si3.960lool<,lo(OH)i.9o The analysis shows a few tenths of a percent excess H 20 and this is con sidered due to analytical error. The small amounts of Fe, Mn, Al, Ca, etc., shown to be present are assumed to be mainly due to the small amount of tremolite. Partial chemical analysis for H 20 and fluorine were also made of talc 1(Ga-n1d7)3)a.nFdlutroerminoelaitnea(lGys-e2s11)fosarma pnluemd bfreormoftohtehAerrntaollcdsppietciinme1n9s66ob(Ttaaibnleeds 1The samples were fused in 3.5 grs of sodium carbonate, cooled and leached out in weak sulfuric acid. Samples were then transferred to stills and 100-125 ml. of 1:2 H2SO1 TRICU N IC TALC FROM GOUVERNEUR 755 T able 1. Spectrographic Analyses of T alc and T remolite 'ROM THE Gouverneur T alc D istrict, N ew York Talc 'L'ale Talc Tremolite Tremolite (G-l)'* (G-l )' (G-17)c (G-21)d (G-24)' Si > 1 0 ', 20 40 20-40 20-40 Mg >10 20-40 20-40 15-30 Fe 0 03 0 1 0 1 0.2 Mu 0.03 0.01 <0.005 0.3 Al 0 03 0 1 0 05 0.2 Ti 0.001 0.01 0.005 0 02 Ni < 0 005 < 0 005 <0.005 Cu <0.005 <0 005 <0.005 Li 0.001 0.005 0.005 0.02 Na 0.01 0.05 0 05 0 5 K 0 001 0 01 0 02 0.1 Ca 0.03 0.2 0.1 5-15 Sr -- <0.005 - Ba - - <0.005 - -- F 1 0 -- -- 0.30 20-40 10-20 0.1 1-2 0.3-1.0 0.03 -- -- -- 0.1-0.3 0 1-0.3 5-15 -- -- 0.31 " Arnold pit, Analyst: C. L Waring, U. S. Geological Survey. b Arnold pit, Analyst: Bernard Snyder, Battelle Memorial Institute. 0 Arnold pit, Analyst: Bernard Snyder. **Arnold pit, lavender tremolite, Analyst: Bernard Snyder. 0 -- not looked for. 1 Colorless tremolite, 3/4 mile S\V of Wight mine, Balmat, N. Y., Analyst: Bernard Snyder. By wet chemical analysis. frraonmge wofofrlludowriidnee cloocnatleintitesinwtheirse mmiandeeralt.oTohbetsaeinflumoroirnee kannoalwylseedsgaereognivthene in Table 4. tPwhoysdicisatlinpcrtophearbtiietss.;-o-nTeavlcarsipeetyciims efinnse cgorlaliencetdedsofrmomewthhaet fAibrnrooulds ipnitnashtuorwe (G-16) and is associated with white tremolite. The second variety is coarsely crystalline (0-1, 17), often occurring in nearly mono-minerallic zones. Only the coarse variety was studied by X-ray techniques. The coarsely crystalline talc forms platy crystals up to 1 cm in width. The crystals are pure white, translucent, with a slight adamantine luster. Some crystals grow as nearly perfect pseudotrigonal pyramids lying on (001). Often the pyramids are truncated by a small (001) face. added (volume kept below 150 ml.) Fluoride was separated from interfering substances according to the method of Willard and W inter (steam distillation at 165C). The distillate was collected in 500 ml. volumetric llasks Fluoride content of the distillate was then de termined by a thorium nitrate colorimetric titration. 756 MALCOLM ROSS, WIL LIAM L. 5 .1/ 777/ AND WILLIAM II AS1IL0N T able 2. Chemical Analasfs of T alc (G -1 ) from Arnold P it , Fow ler, N G -l" Ratios1' Ideal** Site 62 68 3 958 63 37 MgO 32 33 3 042 31 88 F 0 48 0 096 -- FLO ( - ) 0 33 - - H ,0 i + ) 4 79 1 009 4.75 100.00 total 0 = F/2 100.61 -0 .2 0 100 41 ' Arnold pit, collected in 1961, Analysts' Joan Lathouse and R. I) Foltz, Battelle Memorial Institute b0 RMagtjiSoisiOcua,l(cOuHla)toed on basis of M g+Si = 7.000. Ten talc crystals from sample G-l were examined with the Buerger precession camera. All crystals gave identical unit-cell parameters; the best measurements are given in Table 5. This talc is triclinic; the space group is Cl or Cl, and the structure type is one-layer triclinic (ITc). In contrast to photographs of the common micas, the 0kl and hk0 precession pTprhheoectreoesgsirisoaplnihttspl.ehoXatp-orpgaaryraeppnhotswmdsohenorowdcaliatnaicsftoprrosnethguidsotrmsiycalmitnemircieatlirnyatreiennsgaiintvyyenodfiisntthrTiebauXbtl-ieoran6y.. Two talc crystals from sample G-17, one crystal from a sample from sthame ,"TNaolcrt"hmCinaer,olGinoau,vesarnmepulre, X(C. SY-.2)(CwS-e1r)e aanlsdoosnteudcireydstablyfropmrecaesBsioaln T uile 3 I luorinf. and H ,0 Anal\ ses for T alc and T remolite* Total loss (HjO-l-F) in weight percent -- to 110 110-550 550 1000 F HA) (+ ) -- Talc (G-l) -- Obs Calc. 0 33 0 .0 4.'75071: 4 99 0 48 0 48 4 79 4 51 -- Talc (G1---17) -- Obs --Calc 0.12 0 0 0 19 4 33f 4.96 0 42 0.-12 4 10 4 54 --Tremolite (G-21 -- Obs. Calc. 0 05 0 0 0.11, 1.45' 2 3 ` 0 30 0 30 1 26 2.07 * Analyst. Joan Lathouse, Battelle Memorial Institute. 758 MALCOLM ROSS, WILLIAM L. SMITH AND WILLIAM II. ASHTON T able 5. U n it-Cell D ata for T alc Arnoldpit, G-l Ca pb a (A) b c ((AA)) 7aa 999980905.150442354'677g'0' 1982894550..425052579'37os'6' System triclinio trichnic Diffractionsymbol IC* IP* Structure type ITc ITc AF h 19828596055063244''790' trichnic I.P* ITc BCDE 1958 821160 1598.128378 1598..192347 1000' 10015' 10040' 1859 921558st 9930' monoclinic monoclinic monochmc monochmc C*/c C*/c - - 2Mi 2Mt 2Mi 2Mi abABECDCP--ZsRGHSseetvaertetyutynmtiainnndngpeegrgilirrnec(ka((paac1nsrnno9ed(d3ndf1e4vB9BrP)err,3nioer8nHitdwn)iso,adknsnrHleefea(rtoayl1tirr(9nsdf1G6eog96t9Cr)4t)d.i69,on0)uHgC)n),oa.tMruyfn,oatMrynd,cdhCMuordui.an.ty, Md. tecRhonsiqs,ueTsa.kAedlla,giavned tWheonseasm(e19u6n6i)t-hcealvledsahtoawnasththaat tmgainvyenmiincaTsaabmleple5s. farroemcoamgpiovseendlaoyfemr osirleicathteansamonpelepsohlyotuylpdeb. eTehxuasmainendumbebfeorreofascsruymstianlgs btheesosp. eOcuimr epnreissenhtomstougdeynecoouusp.leTdawlcithG-tlhafrtoomf RthaeynAerrnoalnddpBitroawppne(a1r9s66to) suggests that most talc is triclinic. Previous reports of the monoclinic form may be in error. Unit-cell data for talcs studied previously are compared to that of the Arnold pit talc in Table 5. X-ray data for sample G-l is given both in the Cm-acyenbteerceodmspetatriendg taondtheinraescuoltnsvoefntRioanyanleprraimnditiBvreowcenll. sTehtteintgrasnosftohramt ait ctieolln ism: a1t0ri0x1--fro1m/2 --the1/2C-0c1e0n0te1r.eTdhuenCit--cceelnltetoredthesecttoinngveinstiporneafelrprerdimfiotirviet facilitates comparison with other layer silicate structures. Rayner and B19r3o8wnandexparmoibnaebdlythise aslsaomiedesnpteicciaml eton tahsattheaxtamstiundeidedbybyGrHuneenrdrinick1s93i4n. Thus, the only evidence for a two-layer monoclinic talc is the work of Stemple and Brindley (1960) and Zvyagin and Pinsker (1949). The optical properties of the Arnold pit talc (G-l) are: biaxial positive, optic angle variable ranging from 0 to 10, a = 1.545 + 0.002, = y = 1.584 + 0.002. The value of the optic angle is highly dependent on the TRICLINIC TALC FROM COCVFRNFCR 757 T able 4. Fluorine A naiases of T alc from Various Locutions \ nt>Origins Sample Location and Origin ' ( I' G-l G-17 YYA-3 42771 E 23 25 30 26 11 S 423 7 8 31 29 32 28 14 33 WA-lb 3 27 13 Gouverneur talc district. New York 0 48 Gouverneur talc district, New York .42 Gouverneur talc district, New York, .45 metamorphosed magnesian carbonate sediments. Val Chisone, Italy .44 Val Chisone, Italy -31 metamorphosed magnesian carbonate sediments. Murphy, North Carolina, .36 metasomatic replacement of magnesian carbonate sediments. Inyo County, California, .34 replacement of quartzite along dolomite contact. Brumado, Bahia, Brazil. .29 magnesia metasomatism of siliceous carbonate sediments. Casa Nova, Bahia, Brazil, .27 lenses of replaced siliceous magnesian carbonate sediments. Windsor County, Vermont, 26 schistose talc-carbonate rock, not of jltrabasic origin, but asso ciated with ultrabasic body Allamoore, Texas, .20 metamorphism of interbedded limestone and magnesia rich tuff. Madoc, Ontario, Canada, .18 metamorphosed magnesian carbonate sediments. Dillon, Montana, 18 replacement of dolomite in fracture zones. Flinders Range, South Australia, 17 metasomatism of silicified magnesian carbonate sediments. Esmeralda Count), Nevada, .17 metamorphosed quartzite lens in dolomite. Tong \ ang, South Korea. .16 metamorphosed magnesian carbonate sediments. Dausa. Rajasthan. India, 11 metamorphosed magnesian carbonate sediments. Tamaulipas, Mexico, 04 hulrotherm ally altered basic dike, enclosed in seqientinized schist. Lamoille C ount), Vermont, .04 automorphic alteration of ultrabasic rock, associated with serpentine. Zambales, Philippines, .01 altered ultrabasic rock, associated with serpentine. Transvaal, South Africa, .007 altered ultrabasic rock, associated with seqientine. Providence County, Rhode Island, .004 associated with serpentine pods in greenstone. Note: Sediments refers to metamorphic rocks of sedimentary origin. X* TRICLINIC TALC FROM GOUVERNEUR 759 T able 6. O bserved" and C alculated11X -R ay P ow der D ata for T alc (G -l) from th e A rnold P it , G o u v er n eu r , N. Y ., M in in g D istrict C-setting hkl P-setting hkl d (calc.) A d (obs.) A T 001 001 9.333 9.34 vs 002 002 4.667 4.68 w 020 010 4.568 4.56 s 110 100 4.531 110 T10 4.523 I I I 111 4.316 111 101 4 298 021 Oil 4.125 4.14 vw 021 Oil 4 082/ 111 101 3 8851 3.85 vw 111 111 3.862/ 112 112 3.5041 3.43 w 112 102 3.481' 022 012 3 287 022 02 3 243 003 003 3.111 3.115 s 112 102 3.061 112 112 3.040 F13 113 2 751 113 T03 2.733 T30 110 2.632 130 120 2 627 2.632 wm 201 211 2 617 200 210 2 606) 2.598 m T31 121 2.590/ 023 013 2.588 T31 111 2.578 023 03 2 555 131 111 2 490 2.48 s-d 131 121 2.472' 202 212 2.442 113 103 2.424 201 211 2.415 113 113 2.409 132 122 2 382 132 H 2 2 361 004 004 2 333 2.336 vw " CuK a radiation, Ni filter (X= 1.5418 A). Camera diameter: 114.59 mm. Lower limit 26 measurable: approximately 8 (li.o A). b Calculated from the following unit-cell parameters: a = 5.275, 5 = 9 137, c = 9.448 A, a = 9046', jS= 9855', 7 = 900', space group Cl. All calculated spacings are given to = 2.284 A. 5 vs (very strong), s (strong). ms (medium strong), m ( medium), wm (weak medium), w (weak), vw (very weak), d (diffuse). 760 MALCOLM ROSS, WILLIAM L. SMI TH A M ) WILLIAM // ASI1TOS T able 6. (Continued) C-setting hkl P-setting hkl d (calc.) A d lobs) A /" 040 020 2 284 2.284 v\\ 2 219 m-d 2.103 m-d 1 994 \vm 1 871 m 1.731 w 1 688 vw-d 1.558 \\ 1.527 ms 1.515 w 1 320 \\ 1.296 w 1.271 vw amount of twinning in the crystal; highly twinned crystals have low optic angles. A aiphiboi.es Cspheecmimiceanlsp;roonpeerltaievse.n- d-Terwtoo vpainriketiinescoolfortr(eGm-o1l9i,te21o)c,ctuhreinoththeer pAurrneolwdhpitiet (G-16, 17). The lavender form occurs in large prismatic crystals several millimeters long. The varietal name "hexagonite" is often used to de scribe this tremolite; the type material reported as coming from Edwards, St. Lawrence Count}', X. Y. (Dana, 1892, p. 389, 393). The white variety of tremolite is associated with the "limy talc" (G-16) and to a small ex tent, with the coarsely crystalline talcs (G-l, 17). The lavender tremolite occurs in nearly mono-mineralic zones between the massive talc ore and hanAgninegxwceaplltiodnoalollmyitew.ell-cr\stallized colorless tremolite rock collected 3Sp4ecotfroagrmapilheicsoauntahlwyseesst ooff tthhee Wlavigehnldemr inaendwacsoloalrsleossexvaamriienteieds (G(G-2-241)., G-24) are given in Table 1. Quantitative analyses for H2Q and fluorine for the G-21 tremolite are given in Table 3. The analyzed samples (7-21 andEnGge-2l4(1c9o6n2t,aipn. a30s9m)agllivaems ocuonmtpolfetteiromdiinteeraalndanqaulyasretzs. for two tremolites collected from the old Arnold mine. These analyses are recalculated in our Table 7, The various analyses (Table 1, 7) show that the Gouver nAeIun2r+,trKe,maonlditeXs ahraevpelacaingnecaarllcyiumen,dF-mreepmlabceirngco(OmHpo),siatinodn Aw1 irtehplascoimnge Si. There are four different occupied cation sites in the tremolite crystal 762 MALCOLM ROSS, WILLIAM L. SM ITH AND WILLIAM II. ASHTON T able 8. U nit-Cell D ata for T remolites from the Gouverneur, N ew York T alc D istrict G-2D G-24 G-16d a (A) b (A) C () 0v (A3) System Single crystal Powder1' Single crystal Pow der1' Single cr\ st 9 8U 18.04 3.276 10430' 904.4 9.818 (5) 18.047(8) 3.275(3) 10439' (3') 904.2 (6) 9.796 18.04 S.28, 10425' 903.9 9.812 (2) 18.077 (3) 5.273 10443' ((T2)) 904 5 (3) 9.81s 18.04 5.281 10435' 904.2 monoclinic monoclinic monoclinic Diffraction symbol C** C*/* C*/* a Lavender tremolite, Arnold pit, St. Lawrence County, N. Y. b Obtained from least-squares refinement of powder data given in Table 9. Errors in thousandths of an Angstrom and minutes given in parentheses. 0 W hite tremolite, 3/4 mile SVV Wight mine, N. Y. d White tremolite, Arnold pit, St Lawrence County, N. Y. c= 5.276, and /3=10430'. The hOl precession photographs exposed to ssupunmofitlmstearrreeipdzreedmseoinnlytiTbnadgbelnaeu8ms.ecXroa-ndrdaiayptiphooanswefd.oerXr d-1r0aa0tya hfdooaurtrtasresfmohroowltihteiesxGttr-r2eem4meaolnylditewGe-a2ar1ke are given in Table 9. Spectrographic analysis was given in Table 1. In addition to lavender tremolite described above two white tremo lites (G-16, G-24) were examined by X-ray single crystal techniques. Both tremolites show, under crossed nicols, thin lamellae oriented parallel btoePtshreeeecne(1ssi0ni1o)nthppelahnhoetao.ngdIrnaspsphaemscipomfleebnGot-wh2i4tshptheaceilmloawemnesplolgawieveerarubeninsitoo-ccdueillslatridnmacttiactrhcolesoycsoecpateno. that of the lavender tremolite (Table 8). Superimposed on the strong single-crystal patterns of the host tremolite phase is a weaker pattern of garsoeucponsdymammpehtirbyolPe.2T\hmisosrecPo2n\d wphitahseUi-s-9a.4cl8inAo-,am=ph1i8b.o03le, hca=v5in.2g9,spaancde /=T1h0e1u5n5i'.t-cell data for the P 2\'m amphiboles (G-16 and G-24) are given in Table 10 where the data is compared to that obtained by Bown (1966) on a similar specimen. As pointed out by Bown, who first reported existence of this P2\!m amphibole, Ihe two coexisting amphibole phases have a common -axis with the -dimensions almost identical. The TktCIJ.XlC TALC FROM G0UY1.RNF.UR 761 Table 7. T remolite ( 'h em ic \ i. A nabases from Engel (1962, p 309) Weight percent Atomic ratios' 9" 151' 9b 15 SiO. 57 83 57 76 Si 7 915 7.897! 8 001 AbO, 0 57 0.64 A1 0 092'> 8 028 0 104) 1'e.Oj MgO EeO TiO, 0 20 0 00 24 25 24.73 0 11 0.14 0 03 0.05 MFFcegJ2t' Ti 0 0211 4.945| 0 0121 5 285 0 0031 5 038] 0.016 5 066 0.005 MnO 2 81 0.06 Mn'* 0 325 0 007, CaO 11.42 13 27 Ca 1 675 1.944 KjO 0 14 0 09 K 0 025 ! 1 744 0 016) 2 033 Na-.O 0.17 0 28 Xa 0 044! 0 073 H.O - 0 06 0 13 h 2o + F 2.09 2.38 0 41 0 26 Or H 1 907 (1.820) 2.170 (1 882) 0 178' 0 180 0 113) 0 118 Cl 0 01 0 02 Cl 0 002! 0 005/ C 02 0.00 - 100 10 99.81 0 = E+ C1 0 17 0 11 99 93 99 70 " Arnold Xo 3 mine, 11th level, l'owler, AT. V. b Arnold mine. 14th level, howler, N. V. ' Number of ions on the basis of, number of osygen atoms = 22 00 and (OH) =2.00F-Cl. ' structure, designated Mi, Mo, M3, and M4. The smaller metal atoms such sauscMh gasanC'da FanedenXtear etnhteerMthj,eMla>r,gaenMd 4Ms:iitsei.teWs iwthheoruearsptrheeselnatrgkenrocwalteidognes of amphibole structure we do not expect any alkalies or alkaline earths to enter the Mi, ML>, or Mj sites. Ideally the M4site should take up 2.00 calcium atoms per formula unit. The small cations, however may enter the M4 sites in appreciable quantities replacing some of the calcium or sodium. Physical properties.- X -ray studies of the lavender and white tremolite were made using both single crystal and X-ray powder techniques. The lavender tremolite specimens (G-19, 21) are essentially mono-mineralic. The crystals appear optically perfect with no evidence of twinning, exsolution or alteration. Single crystal photographs show tremolite G-21 to be monoclinic, space group C2 m, Cm, or C2 with a = 9.81eA, b= 18.04, TRICLINIC TALC FROM GOUVERNEUR 763 T able 9. Observed" and CALctTLATEDb X-Ray P owder D ata for W hite (G-24) and L avender (G-21) T rf.molite from the Gouverneur, N. V. M ining D istrict Tremolite, G-24 hkl d (calc ) A" d (obs) A / Tremolite, G-21 d (calc.) Ad d (obs) I 020 9.039 9.054 15 9.024 110 8 403 8.410 40 8.405 001 5.100 5.092 20 5.103 130 5.087 5.082 5.046 60 111 4.873 4.875 10 4.873 4 866 5 200 4.745 4.751 10 4.749 4 739 10 040 4.519 4.523 30 4.512 4.514 10 021 4.441 4.442 220 4.201 4 209 15 4.203 4.197 50 201 4.020 4.028 5B 4 021 111 3.980 3.984 131 3 875 3.880 15 3.873 3 878 10 221 3 673 3.673 041 3.382 3 3801 131 3 379 3 380 !> 3 373 25 ISO 3.379 240 3.273 3 272 65 33..237714 J 3 274 85 310 3.116 3.120 100+ 3 119 3.115 100+ 201 3.103 3 107 311 3.016 3.016 3 013 5 060 3.013 3.008 241 3 004 3 004 5 3.002 151 2.942 2.944 45 2.939; 2.942 35 221 2.935 2.937] 330 2 801 2.802 25 2.802 331 2 727 2.727 2.727 20 151 2 706 2.712 100+ 2.705 2.709 60 112 2 608 2.609 061 2 594 2.594 35 2.591 2.589 15 241 2.558 2.557 5 2.559 " CuK a radiation, X'i filter (X= 1.5418 A). Pattern taken with N orth American Philips X-ray diffractometer internally standardized with sodium fluoride. Specimens contain a small amount of quartz and tirodite. b All calculated interplanai spacings are given down to if = 2.530 A. Calculated spacings less than this are given only where indexable to an observed spacing. "Calculated from the following unit-cell param eters: a -=9.812 A, =18.077, c= 5.273, 3 = 10443', space group d i m . Composition by electron microprobe anal ysis: d C'ai jM n03Mgs :Si,0lO H , F). Calculated from the following unit-cell parameters: u = 9.818 A, = 18.047, c= 5.275, 3 = 10439', space group C2/m. 764 MALCOLM ROSS, WILLIAM L. SMITH A M ) WILLIAM II. ASHTON T \ ble 9 (Continued) hkl - -- - Trem- o-l-iti*, G-24--- _ _. . -- Tremolite, G-21 _ -- -------- . d leale ) 1 d (obs) A / d (cale.) A'1 d (obsj A I 002 2 550 2.552 260 2 543 2 541 202 2 530 2 530 25 2 530 2.531 20 350 2 381 2 3/9 15 2 380 2 379 100+ 351 2 335 2.334 2 336 45 420 2 295 2 295 20 2 296 2 295 20 312 2 272 2 267 20 2 272 2 268 20 242 2 208 2 207 2.210 5 171 2 182 2.182 5 2 180 2 177 10 132 2.164 2.166 2 164 55 261 2 162 2.161 2 161 25 152 2.130 2 132 5 2 129 202 2 040' 2 043 2.043 5 280 2 040 r 2.046 10 2.038 351 2 015 2 015 25 2 015 2 015 30 370 2 000 1.999 10 1 999 1 998 100+ 190 1 965 1 962 322 1.962 1 961 10 1.962'!> 1 961 15 510 1.888 1 887 30 1 889 1.892 35 460 1.864 1 864 15 1 864 1 864 10 42 1 837 1 836 1.836 10 530 1 810 1 812 1.810 15 441 1.805 1 805 10 1.806 172 1.726 1 725 1 1 720 15 223 1.716 i 716; 372 1 713 1 710 5 1.712 282 1 685 1.685 15 1 684, \ 1 685 10 133 1.683 1 6831 1 675 10 2, 10, 1 1 649 1 646 1 649 40 1.648 30 461 1 648 1.648' 1, 11,0 1 619 1 617 15 1.617 1.618 30 403 1.586 1 586 i(j 1 585 20 600 1 582 1.583! ------------ -- -- -- -- -- -- -- -- _______________ ___1_._5_6_1__ _____5__ (Table continued on jolloing page) llkl 371 402 1, 11. 1 282 263 482 2, 10, 2 0, 12, 1 391 731 TRK LI M C TALC FROM GOUVFRNFLR 765 T \ ble 9. (Continued) Tremolite, G-24 d (calc.) A d lobs) I I remolite, G-21 d (calc.) A'1 d (obs) A / 1.555 1 555 10 1 551 1 524 1 525 10 1.514 1 512 1 511 10 1 502 1.503 20 1 471 1 470 10 1 445 1 445 10 1 433 35 1 398 1 398 10 1.365 1 365 15 1.555 1 5531 1 522 1 514 1.511 1 .501 1.469 1 443 1 554 20 1.530 10 1 514 100+ 1 468 5 1 435 75 aa-nadxeast oafnthanegtlreemofo2lit3e0a' nodf P2\ m amphibole lie in one another. The study a common (010) plane by Bown was made on a tremolite from the Wight mine, St. Lawrence County, X. Y. showing "extremely fine (001) lamellae." His material is probably very similar in composition to specimens G-16 and G-24. In the 12; m setting of Bown T able 10 U n it-C ell D at \ for th e Slcond A m bhibole P hase Kxsoi.vf.d from th e G ouvf.r n eu r T rem olites G-2T* G-161' Bonn (1966)' cummtings "tom.te11. a (A) b (A) c () d V (Ab S\ stem Diffraction s\ mbol 9 50. 18 04 5 28, 10225' 884 6 monochnic T 2 ,/, 9 47,, 18.03 5 28;, 10155' 883 5 monoclinic 752 , / ,, 9 51 17 95 5 27 1020' 880 0 monoclmic P2i/* 9 467 17 937 5.292 102 14' 878 1 monochnic c++ a D ata obtained from the same single c n stal patterns as those of tremolite G-24 (Table 8). ,J D ata obtained from the same single c n stal patterns as those of tremolite G-16 (Table 8) 0 Cell edges transformed from the /-centered cell: tz= 9.87 A, = 17 95, r = 5 27, 0 = 109.5, space group 12/m d Unit-cell data of an iron free cumnnngtonite, M grShOm(OH):, as extrapolated b\ Viswanathan and Ghose (1965) 766 MALCOLM ROSS, W ILLIAM L. SMITH AND WILLIAM II. ASHTON the lamellae are oriented parallel to the (001) plane. Bown suggested that the lamellae are clino-anthophyllite. Ross, Papike and Weiblen (1968) have made a more complete study of the composition and structural state of the amphiboles in sample G-24 and also have studied a sample of the manganoan amphibole tiiodite (Segeler, 1961) from the International Talc mine No. 3 in the nearbv Talcville, N. Y. area. X-ray precession photos and least-squares powder 0re.0fi0n1emAen, t 6o=f18ti.r0o0d7it+e0.g0i0v3e, thce= 5fo.2ll9o8w+in0g.00u1n,it-0ce=ll10d2at3a9:' +a 1=',9.5s5p0ac+e group P2\/m or P2\. The single crystal photos also show a weaker pattern of a second amphibole oriented parallel to the (101) plane of tirodite. The unit-cell data for this second phase is: a = 9.78 A, 6=17.99, t;= 5.27, /3= 10425', space group C2/m. The (101) lamellae can be seen optically in the tirodite grains. Electron microprobe scans over the Talcville tiro dite give the approximate composition as Ca0iMn] 2Mg64Si8022( 0 H ,F )2. The lamellae are about one micron thick and have a much highei calcium and lower manganese content than the host tirodite phase. Microprobe examination of sample G-24 shows that in addition to the crystals of calcium-rich tremolite there are a few grains of a manganese- rich amphibole. The lamellae in the tremolite are manganese-rich and similar in composition to tirodite. The lamellae in the Mn-rich amphi bole are calcium-rich. The approximate compositions of the tremolite and Ca0 Mn-rich host 2M n09Mg6.9Si80 phase 22(0 H , s F are )2 res pCeac4ti6vMelnyo..3 Mg5.2Si80 Chemical 22(OF[, and X F -r )2 ay and evi dence leaves no doubt that sample G-24 contains two amphiboles, tremolite and tirodite, with tremolite exsolving tirodite and tirodite exsolving tremolite. It is estimated that tirodite composes about 5 weight percent of the sample. The tirodite sample from Talcville is an analogue to sample G-24, the major phase is tirodite, the minor exsolved phase is tremolite. In order to obtain more precise unit-cell data for the lavender and white tremolites (G-21 and G-24) the X-ray powder diffractometer data (Table 9) was subjected to least-squares refinement. The refined param eters are compared to the single crystal X-ray data in Table 8. The amount of tirodite in sample G-21 is probably less than one weight per cent and in sample G-24, probably less than 5 weight percent. No lines of tirodite could be detected in either sample and thus should not have effected the refinement. The optical properties of all three tremolites studied (G-16, G-21 and G-24) are nearly identical (biaxial negative, a = 1.604 + 0.002, 3= 1.612 T+h0e.0l0a2veanndde7r = 1.628 variety + 0.002), does not suggesting similar chemical show (lOT) lamellae althou compositions. gh the X-ray TRICLINIC TALC FROM CONCERNEUR 767 pbhuot tcoogmrappohssinsghporwobdaebfilnyitleelsys tthhaant othnee sveoclounmdeapmerpcheinbtoloef pthheasceryisstpalr.esTehnet lamellae are much more pronounced in G-16 and G-24 and the X-ray diffraction single crystal patterns of the lamellae are relatively strong with many reflections appearing in the AO/, hll, and h2l nets. D iscussion rToaclkcs.--, bTyaltchedreeppolsaictesmmenaty offosrimlicifbieyd tchaerbomneattaemroorcpkhsi,somr boyf tchaerbaoltneartae tion of ultramafic rocks. There are reported occurrences of talc formed from mafic and felsic igneous rocks, pegmatites, tuff, and low magnesian sediments; however, these involve complex and unique conditions that are atypical of the major occurrences. Talc bodies may also form by contact metamorphism in rare instances where the chemical conditions taereeTnwcdoeirnfrfteyecr-tet.wntodseppeocsiimtsenhsavoef beesesnenatinaalllyyzpedurefortafllcuoorbintaeinceodntfernotm(Tnaibnlee 4). All of the talc samples were found to contain fluorine. Although too few samples have been studied to permit firm conclusions to be drawn, the(af)oTlloawlcinfgromreldateipoonssihtsipbsemlieavyedbetoinbfeerdreerdi:ved from the metamorphism coaf rcbaornbaotneatreocskesd,imorenoctacruyrrirnogckisn, ftoalrcm-ceadrbboynathtee-armepplahcibeomleenstcohfisstsil,icwifeierde fou(nb)d Ttoalccofnrtoamin t0h.1e1fitvoe0d.4e8popseitrscebnetlifelvueodrintoe. be derived from the altera tion of mafic or ultramafic rock, and which are intimately associated with serpentine, show fluorine content below 0.04 percent. The present study coupled with that of Rayner and Brown (1966) dcleifniincitestlryucshtuorwe.s Othtahterthpeolcyotympmeso,n ifvatrhieeyty oocfcutralcwihllaspraoboanbel-ylaybeer rtarrie compared to the ITc form. To summarize, talcs from the following localities have been shown to have the one-layer triclinic structure: ((12)) HAranrfooldrdpCit,ouSnt.tyL,aMwraernycleanCdo, uUnt.}S-.,NN.Mew. 8Y25o1rk9 ((34)) "BTalaslacm" ,mNinoer,thSt.CLaarowlirnean.ce County, New York Tremolile.--Engel and Engel (1968) suggest that the temperature of mroafnectgaaeml.cioSurompmheiasnomdf tishnoedthtirueemmGoo(elui.tvge.e,srnTweaeubrrelemen7inr,iicnahngeaddlyisisntirsimc9tabni)ng. atTnhheeseeisea5vt0id0thenetcoeex6pg0ei0vnesCne by Ross, Papike and Weiblen (1968) shows that the manganese-enriched 768 MALCOLM LOSS, WILLIAM L. SMITH AND WILLIAM II. ASHTON tremolite coexisted with a second amphibole tirodite which was enriched in calcium. On cooling both phases unmixed to produce the (101) laabmleelqlauea.nAtitpiepsaroefntmlyanagt ahniegshe.teTmhpeeraaptpueraersanthcee Mofi esxitseolcuatnionholladmaeplplareeciin tGreomuvoelirtneeushr osuclhdisbtse avnedrycaunseafulsloingivuendinefrosrtamnadtiinogn tohne thpaeraegxetennetsiosfosfoltihde solution in tremolites. Alteration of the tremoliie-bearing schists. --Optical and X-ray examina ftioollnowofinag nruemtrobgerradofe tareltmeroaltiitoenroscekqsuefnrocmes:the Gouverneur aiea show the (1) Sample CS-1, "Talc" mine tremolite + talc-->an:hophyllite + talc (2) (3) Sample Sample G-2, G-6, IFntotrweermlnearo,tliiXoten.--aYl .atanltchompihnyel,liXte.--YH.a;leG-5, Fullerville, X. Y. (4) Sample G-18, Aronoalndthpoitphyllite--talc tre m o lite --serpentine (5) Sample G-26, Wight mine tre m o lite -- an th oph yllite--talc? Tremolites CS-1, G-5, and G-26 show prominent exsolution lamellae. Stenrple and Brindley (1960) give evidence for the transformation itnreAtmhlleoloiGfteot--uhveteavrlnceeritun' rfaisncsehpeigscrtisamianepenpdferatoarmlct,othahenatxhGreoopguhrvoyewlrlnniteebu,yr aaanrdelaa.stteerrpeanltteinraetinoonteodf tremolite or anthophyllite. The coarsely crystalline talc (e.g., G-l, G-17) is associated with clear unaltered tremolite and appears to be a primary metamorphic assemblage; not a result of any retrograde alteration. The cpooaorrsemlyillicnrgysqtaulalilnitey. tTalhce ifsinen-ogtravinaeludaballetercaotimonmeprrcoidalulcytsboefcathuseeamofphitis qboulaelsity(e.go.f, tGh-i1s6,orGe -1is8)prfoorbmabslytheduceomtomethrceialfinoere-g. rTaihneedsunpaetruiorer mofillitnhge magnesium silicate alteration products. Acknowledgements We wish to thank M argaret H. Appleman for preparing the tremolite X-ray powder patterns and handling the computer computations, Paul W. Weihlen of the University of Minnesota for the electron probe analysis, and James J. Papike for advice on amphibole crystal chemistry. References Bowasn, tMho.pGhyl(l1it9e6'6A)mAern. eMwinaemrpahl.i,b5o1l,e 2p5o9l-y2m60o.iph in intergrowth with tremolite: Clino- TRICLINIC TALC FROM GOUVERNEUR 767 photographs show definitely that the second amphibole phase is present but composing probably less than one volume percent of the crystal. The ldwaimiftfhrealmlcateaionnavresrienmfgleuleccthicornmyssotarapelppperaaortntineorgunnisnceotdfhetihnAeOG/l,-a1Am6le/,lalanandedaGhr-e22l4rneealatnstd.ivethlye sXtr-ornayg D iscussion Talc.--Talc deposits may form by the metamorphism of carbonate rocks, by the replacement of silicified carbonate rocks, or by the altera ftiroonm omf aufilctraamndaffieclsircocikgsn.eoTuhserroeckasr,e preegpmoratetidteso,cctuufrfr,enacneds loofwtamlcagfnoermsiaend sediments; however, these involve complex and unique conditions that are atypical of the major occurrences. Talc bodies may also form by contact metamorphism in rare instances where the chemical conditions are correct. Twenty-two specimens of essentially pure talc obtained from nine 4te)e. nAldlifoffertehnet tadlecpossaimtsplheasvwe ebreeefnouanndaltyozecdonftoarinflfulouroirnienec. oAnlttehnotug(Thatboloe few samples have been studied to permit firm conclusions to be drawn, the following relationships may be inferred: (a) Talc from deposits believed to be derived from the metamorphism of carbonate sedimentary rocks, formed by the replacement of silicified cfoaur(bbn)odnTtaoatelccorfnortcoakmisn, t0ho.1re1ofictvoceu0dr.r4ei8npgopseiintrscetbaneltlci-felcvuaeordrbiontoen.abtee-admerpivheidboflreomschthisetsa, ltweerrae twioitnh osfermpeanftiicneo,r suhlotwramflaufoircinreoccko,ntaenndt bwelhoiwch0a.0r4e pinetricmenatt.ely associated The present study coupled with that of Rayner and Brown (1966) definitely shows that the common variety of talc has a one-layer tri ccloloicnmailcpitaisreetsrduhcattovueretbh. eeeOnItThsehcrowfponorlmyto.tyhpTaeovs,esuitfhmetmhoeanyreiz-oleac,yceutarrlctrwsicillflirnopimcrosbttahrubeclytfuorbleleo:wrainrge (1) Harford County, Maryland, U.S.N.M. 82519 (2) Arnold pit, St. Lawrence County, New York (3) "Talc" mine, St. Lawrence County, New York (4) Balsam, North Carolina. Tremolile.--Engel and Engel (1968) suggest that the temperature of mranegtaem. oSropmheisomf tihnethtreemGooluitveesrnweeurre meninriicnhgeddiisntrmictaningatnheeseis a5t00thetoex6p0e0nsCe bofy cRaolcsisu,mPaapnikdesaonddiumWe(ieb.lge.,n T(1a9b6le8)7s,haonwaslytshiast9tbh)e. mTahnegeavniedseen-ecnerigcihveedn TRICLINIC T 1LC FROM GOUVERNEUR 7(0 D ana, E. S. (1892) System oj Mineralogy. 6th ed John Wiley and Sons, Inc., New Vork E ngel, A. E. J. (1962) The Precambrian geology and talc deposits of the Balmat-Edwards District, northwest Adirondack M ountains, Xe Vork. U S. Geol S u n Open File Rep , 357p. E ngel, A. E J. and C eleste G. tion of the major paragneiss, Engel (1958) Progressive metamorphism and northwest Adirondack M ountains, New Vork granitizaGeol Soc Amer. Bull . 69, 1368-1414. G rner, J. W (1934) 1'he crystal structures of talc and pyrophy Hite. Z. Kristallogr , 88, 412-419. H endricks, S. B. (1938) On the c n sta l structure ol talc and pyrophyllile. Z. Kristallogi., 99, 264 -274. R a w e r , J. H and G. B rown (1966) Triclinic form of talc Nature, 212, 1352 1353 Ross, M., H T akeda and identification. SancidenDce. ,R151V,Vo19n1e-s19(31966) Mica polytypes Systematic description Ross, M , J. J. P.apike and P aul \V. VVfjblen (1968) Exsolution in clinoamphiboles Science (in press). Seg eMleinre,rCa.l.G4.6(,1693671-)6I4'i1r.st C S occurrence of manganoan cummingtonite, tirodite .1 liter St e m ple, I. S. relations. Ja.nAdmGer.WC.erBarmi.nSdolcey43(1, 93640-)42A. structural study of talc and talc-tremolite Visw anathax, K. and S G hosf. (1965) The effect of M g2+--Ee-'+ substitutions on the cell dimensions of cummingtonites Amer. Mineral. 50, 1106-1112. Zvyagin, B. B. and Z G. P insker (1949) Electronographic determination of the elementary cells of pyrophyllile and talc and structural relation of these minerals to montmoril Ionite Dokl. A cad. Sei. I 'SSR 68, 505 Mamiscript received, July 18, 967; accepted tor publication, September 25, 1967.