Document ExkGnxD54rjM7Z5BgmNbVpkKn

FILE NAME: Talc (TALC) DATE: 1977 July DOC#: TALC142 DOCUMENT DESCRIPTION: National Bureau of Standards Special Publication - Workshop Proceedings - Misidentification of Asbestos in Talc ,, ... .. _ rnc proceedings of the Workshop on iQ77. (Issued November 1978} MISIDENTIFICATION OF ASBESTOS IN TALC Jerome B. Krause Colorado School of Mines Research Institute Golden, Colorado 80401 and William H. Ashton Johnson 4 Johnson Abstract Both optical microscopy and x-ray d^ aCti0pJcal* microscopy can to d e t e c t minerals associated with a ^ always fully identify determine the morphology of a pa^tii:le, biJ^ can1n1; * screening technique the specific mineral. Although XTOIs an exc.. method can for the detection of I**. misidentify minerals due to Interferences, mcerp errors, and the Inability to determine morphology. Methods for reduction ^ 6limt1^ nt1ad x-ray^iffraction, combined a is ^ s n is ri E r a - Introduction ' There are many ways to analyze and study rexperti se^^ interest 2 conclusions reached will t^tuat^o^sums upP*he of the investigator. ThatJ? " Icsocirted with present status "asbestos"; and w m taic. of it "asbestos11; 1s becoming it istatus the status Popular methods of analysis Ca^ (^^dentfMcation)- is not so much one of present when it certainly is not. That P " M ,,interpretation of data and failure to limitations of the methods, b r t n ^ r m e tQ certify Blneral purity, for example recognize the mineralogical background d unfortunately, one main factor is tha when analyzing sheet silicates fr i(rition`s depending on whether the point of view is asbestos has now developed variable defin i ? T^e edical definition is most mineralogical, industrial. ,, r t i S w are biologically active; the industrial^ concerned with whether flexibility and weavability; the meralogic s r : = ^ u n W as f ; < . tf, TM . i * " , i M ,mi Th, word "asbestos" sto.` fihrmis industrial mineral product. Since asbest r F, g U res in brackets""Indicate the meratore rentes toins related*to combined mineralogical and tt,s at the end of this paper. C O A Cin / tr\A f 2063105132 I tt&tSfFxSZ 3 ^ " ~ ^ r t ( ? L S * * < * * - b" " *b`" *d - , i*--. and i t is not our intent ,, , ,, 1 , m u x , .a K t,.n tiflctto , f **" . v w ^ - s s ? a w a S S S i- T i W i.T A .i . * " "> Chemical Composition rrunnnsition, and that A pearl, an oyster shell, o S v i u s l V ^ ^ ^ en0t nat6ralS' and minerals aragonite f?d .c.af\c^ ,, calcium carbonate. That is to say, yet each will be ^"VdlnUfv t h ^ all as the same substance, where chemical analyses will of chalk, everyone knows that a pearl is not a piece Th ame situation exists in certain phases of ^ e s t o s ^ a1^ 'hydrous magnesium >' m et th* a . i w w ' ,, nor *, . p m tc.ti . ,, . t r S S i ^ ^ * ^ " ^ <&*" s" 1' Wet Chemical Analysis Classical (gravimetrie, volumetric) instrumental (atomic absorption, flame emission) Microproba (electron and ion) Emission Spectrograph Mass Spectrograph X-Ray Fluorescence M S' i'-S ..*,' .ha_v_e',"t.tuhAe "fsaammee cshape. . f e ; - m They ex^t Morphology t 's r j f r . i r a * 'T . l T - 4 ourselves to - j i T S s r minerals wMch - Soccur because shape alone was the index used. u-thndt hased on morphology include: Optical Microscopy Automated Image Analyzers Electron Microscopy (SEM and TEH) 340 as " in u l c r~ r\ - i n r \ 1rs.A -P 2063105133 Ci Structure The configuration of a t TM ie the eey.tai U t t ico.of SKEehST-a^ST determine e mineral speeiee. The u Tha, is to say that methods based on Si!!,ird."o"htt''.ec c ? " i n i 'V S s " h". . . 1 . . / i t s sibling, anti,.rite. Methods of identification which relate to molecular structure are: Infrared Spectroscopy Differential Thermal Analysis X-ray Diffraction Electron Diffraction In general then, no single property defines a mineral, and no single method which depends on one property can identify a specific mineral. Conversely, methods which depend on a single factor or characteristic of a mineral can give misidentifications. Two Popular Methods i laboratories as possible monitoring techniques. the professional procedures. Optical Microscopy hen ea e w f i e h c e d eptic.i a petrographic microscope, he ca" co.me * = s * , SOecific^properties are determined, such as training and wide nineralogical background are required to get the right answer. sp" ,,ic in contrast, current optical methods In S f re?? by such simple oversights as looking at a 9 other shortcomings of those study conducted by Harvard University and NIOSH L*JHnwever there are a few rare cases where abnormal crystal habit can be misleading S H s ? s ; i y i u g . u = b ,ge optical microscopy were used. r S, ; H? , S ' S> t' TM ,` i i/~cf oHi i/tiH/i imn52d00/Ddf 2063105134 V Thus, simple optical microscopy can determine the morphology of a particle, but if used alone it cannot always fully identify the specific mineral observed. X-Ray Diffraction Although x-ray diffraction (XRD) is a valuable technique, it cannot ^ physical shape of a mineral particle, and for that reason it cannot detennine whether or not a sample is asbestos. Furthermore, it cannot distinguish between two mineral varieties in the same mineral class in cases such as the asbestos minerals and their nonasbestiform analogues. It is surprising that such a b a s i c shortcoming continues to b overlooked by responsible investigators alleging to have identified asbestos by XKU. One result of the inability of powder XRD to differentiate between the' " ^ stif"{* and nonasbestiform varieties of a mineral is the potential error of prejudging an XRD detected phase to be the asbestiform variety. For example, preparing calibration standards Pof mixtures of talc plus chrysotile could have the effect of causing a serpentine peak in an unknown sample to be prejudged as the asbestiform v^ 1ety > - < chrvsotile A mixture of talc spiked with the serpentine mineral chrysotile will give the same XRD pattern as a mixture of talc spiked with the very common platy's^pentine mineral antiqorite It should be obvious that an unknown talc showing serpentine Sfeiudged or branded as containing chrysotile asbestos under such circumstances. Unfortunately, the literature has articles by responsible authors who have overlooked that error in logic [5,6,7]. For research purposes only, single crystal XRD can provide Information as to whether or not the specimen could be asbestos. However, due to the difficulty of handlingI specimens, single crystal XRD is inadequate for particles smaller than about 20 x 5 pm, and, of course, is also inadequate for routine monitoring procedures. Amphiboles Each of the five amphibole minerals, anthophyllite, cummingtonite-grunerite, riebeckite, tremolite, and actinolite has an asbestiform variety, namely anthophyllite asbestos, amosite, crocidolite, tremolite asbestos, and actinolite asbestos, respectively. Tremolite asbestos is quite rare, and actinolite asbestos is so rare that a recent NIOSH project to prepare reference standard minerals has been unable to locate a source of pure actinolite asbestos [8]. The amphiboles (named from the Greek "amphibolos," meaning ambiguous) are characterized by similar crystal structure and wide variation in chemical composition and appearance. All amphiboles have XRD patterns which are similar,and are characterized by having their (110) or (210) diffraction peaks occur within 0.2A of each other (Table 1, Figure 1). Reliable identification of individual amphibole species is difficult in the absence of confirming composition data. Examination of Table 1 and Figure 1 illustrates that attempted identification of a specific amphibole on the basis of dc u c o or d h a s good potential for being in error. For example, selection of Joint Committee on Powder Diffraction Standards (JCPOS) card 1 3 - 7 asP being definitive of tremolite presents serious problems. Twenty-nine additional JCPDS amphiboles have their (110) or (210) peaks within iO.l20 of this tremolite (110 peak at 10.5629. Identification of an amphibole as tremolite on the basis of a peak at 10.5629 is obviously an identification with very low reliability. In other words, a peak at that location is not necessarily the mineral tremolite since it could be one of other minerals. c*5 2063105135 342 MtrW/lona/-'\/ lihrarv nr;f priii/tid/umD52d00/Ddf Table 1. Amphibole OCPDS Card No's., d (110) or d (210) peak position, and relative Intensity. iiCPDS card # 3-118 10-456 20-734 20- 378 14-633 21- 149 19- 467 20- 982 23-665 23-664 23-667 23-663 9- 434 13-499 20-556 20-470 23-666 20-469 23-1406 23-1406 20-1310 10- 428 23-603 10-431 19- 1061 20- 481 20-1390 23-302 19- 1063 13-437 17-478 23-495 9-330 17-750 20- 386 22- 531 16- 401 1177--745 725 20-376 17-726 20-434 13-506 23- 679 9-455 20-453 11-253 ' 23-310 13-401 8.58(1) 8.55 1) 8.53(1) 8.520) 8.51(1J 8.51 1 8.50(1) 8.50(1) 8.48(1) 8.47(1) 8.47(1) 8.46(1 8.45(1 8.45(1] 8.45H 8.44{i; 8.44(l) 8.430) 8.43(l) 8.43(1) 8.43(1) 8.42(1) 8.42 1 8.4l(l) -'l 8.40(1) 8.40(l' 8.400, 8.40 1 8.39(1 8,38(' 8.38( 8.38(1', 8.37 1 8.36(l) 8.35 1 8.35(l] 8.33(2 8.33 1 8.33(1] 8.31(1 8.30(l 8.29 1 8.27(2) 8.27 1) 8.26(2) 8.260) 8.23(2) 8.200) 8.11(2) 2Q(Cu) 10.31 10.35 10.37 10.38 10.39 10.39 10.41 10.41 10.43 10.44 10.44 10.46 10.47 10.47 10.47 10.48 10.48 10.49 10.49 10.49 10.49 10.51 10.51 10.52 10.53 10.53 10.53 10.53 10.54 10.56 10.56 10.56 10.57 10.58 10.59 10.59 10.62 10.62 10.66 10.62 10.65 10.67 10.70 10.70 10.71 10.71 10.75 10.79 10.91 100100 70 100 70 55 100 65 45 35 45 11000040 50 100 40 100 80 40 40 100 100 80 100 100 90 100 70 . 100 65 80 100 25 40 30 70 100 100 100 100 100 80 90 55 100 100 75 100 Name' prieskalte ri chterite mboziite dashkesanite arfvedsonlte hornblende _ ferropargasite, syn Hchterite, syn r ichterlte, calciar, syn edenite, sodi an, syn H chterite, calciar, syn eckermanlte, calcian, syn hornblende magnesi oriebecki te magnesloHebeckite crosslte tremo!Ite, sodian, syn hast1ngsIte ` edenIte paragasi te t itremo!Ite, syn Hchterite, fluor, syn rodi te edenite, fluor, syn HebeeMte hornblende winchite cummingtonlte, mangoan Hchterite , tremoli te kaersutite eckermanlte tremo!Ite, fluor, syn Hchterite, fernan eckermanite, syn joesmithite anthophylHte, magnesian, syn grnerIte grunerlte crosslte cummingtonite Hchterite gedrite glaucophane anthophyllite glaucophane ferrogedrite Hchterite, ferrian holmquistite a ( H O ) 1 or (2IO)2 . Maximum i2e(Cu) * 10.91 - 10.31 " 0.6 i S a v : a f f i ? * " - - d / , i M o '* d m o V 343 2063105136 f ori. i/tiH/i imn52dOO/Ddf 0 s> An additional problem further affecting the reliability of identification by XRD Is the effect of shift In peak position caused by slight raispositionlng of the saaP la sur^ f in the instrument. For example, a 100 pflt raispositionlng of the specimen surface will result in a shift of approximately 0.6-0.7 A in d-spacing at low 20 angles [.9]. A slight shift In the position of the peak (from a different amphibole or raispositionlng of the sample surface, for example) could go unnoticed, resulting in misidentificatian of an amphibole that is not even present. In order to conclusively identify an amphibole by XRO, it is n*ce" na7 . A Jlav* th2 essentially complete diffraction pattern. In order to obtain such an XRD pattern, the sample must have a relatively high amphibole content and the pattern must be acquired with a time-consuming slow scan. Acquisition and interpretation of such Patterns is time consuming, and discourages proper application of the full procedure, Y s routine monitoring where large numbers of samples require analysis. Shortened procedures, such as single peak Identification of araphiboles, provide good opportunity for nisidentification. The shortened procedure of single peak identification was apparently used in a 1972 paper [ 7 ] , where our e x am in a tio n of some of th e same samples disagreed with identifications of serpentine, tremolite-actlnollte anthophyllite, and anhydrite. 344 httrv//iianarv lihrarv ucsf edu/tid/umD52d00/pdf 20^3105137 Chiorite-Serpentine Chlorite is one of the most c o m o "h they exhibit a The chlorite group of minerals are som*"h^d n 9 have a similar crystal structure. The wide variation in chemical composi ion (004) are characteristic, and occur diagnostic chlorite basal XRD p k s (001), (002), 1 J f the amphiboles, specific at about 14R, A and 3.5, L" ion " difficult. The XRD problem with identification of a particular chlorite species y k overlaps the chlorite (002) chloritic talcs is that the serpentine peak, and the corresponding serpent ne . ^ basal peak overlaps the chlorite (004) order peaks are separate peak. Generally, however, the chlorite (O ) nresence of both phases when present in s t a . s s a ss. s a w - i 2 J ' 7 X & chlorites 3 Table 2. Chlorite 0CPDS Card No's., d(gg4) peak positions, and relative intensity. 0CPDS card # 10-183 20-671 16-351 12-185 7-160 19-749 7-77 16-362 19-751 22-712 7-165 7-78 7-171 12-242 7-76 13-29 7-166 12-243 21-1227 3-67 O A 3.60 3.60 3.59 3,57 3.58 3.56 3.558 3.55 3.55 3.55 3.545 3.541 3.541 3.54 3.537 3.53 3.523 3.52 3.52 3.49 2 6 (Cu) 24.73 24.73" 24.80 24.94 24.87 25.01 25.03 25.08 25.08 25.08 25.12 25.15 25.15 25.16 25.18 25.23 25.28 25.30 25.30 25.52 I 100 90 70 85 60 80 50 80 65 45 60 60 80 100 50 80 50 92 100 100 &A dOT5) Table 2 illustrates variation in position of Table 2 should be compared * n h T^ l e 3 to Name pennini te kmmererite chlorite lb kotschubeite kotschubeite clinochlore sherldanite chlorite la sudoite nimite grochaulte thuringlte diabantite leuchtenbergite Hpidol ite thuringlte daphnite aphrosiderite thuringlte thuringlte XRD peak. d (0Q4) ^ identification difficult at best. 345 2063105138 f oHi i/tiH/i imnB2d00/Ddf IOOi- 90 80- TO- 60 50 40 30 20 100L 1--------------------------------------------- ------------------ '------- ------ -- --- CHLORITE t 16-562 z \ ---- -------- la 40 > <J ----- u a u 100 cn 90 80 TO 60 50 40 3200 10 0* 24.7 24.8 24.9 25.0 25.1 25.2 25-3 25.4 25.5 DEGREES 2 0 (CaK<O Figure 2. Chlorite - peak positions and relatiwe intensity. The data of Table 2 are presented in graphical form showing the variation in position of the *RD peaks for different chlorites. Selection of JCPDS card 16-362 as diagnostic for chlorite can obviously result in misidentification. 6TS0imz http://legacy.library.ucsf.edu/tid/ump52d00/pdf Table 3. '' Serpentine, __ >Ls n n e itiflfl 1 5 H -.M : S3 !K" "K S c* JCP0S Card # 18-^79 9-444 21-543 7-417 11-386 21-963 12-583 13-4 7-339 11-388 7-315 9-493 A 3.67 3.66 3.65 3.63 3.62 3.61 3.56 3.56 3.55 3.55 3.52 3.52 6-221 14-164 12-447 3.58 3.579 3.56 9-453 3.63 10-446 3.58 2e(Cu) 24.25 24.32 24.39 24.52 24.59 24.66 25.01 25.01 25.08 25.08 25.30 25,30 80 100 70 300 60 80 80 70 100 100 100 100 ( 002) ( 0012) (004) (102) ( 002) ( 002) ( 0012) ( 0012) (002) (0012) ( 002) (004) Serpentines lizardite, 1M antigorite, 60 chrysotile, 2M antigorite. 6M lizardite, 10., alumlnian antigorite, 6H antigorite, 60, aluminian antigorite, 60., aluminian berthierine antigorite, 60., syn berthierine antes ite Kaolinites 24.87 24.88 25.01 100+ 80 50 (002) . (002) (002) kaolinlte, IWd kaolinlte, IT kaolinlte, IT Halloys ite 24.52 90 (002) hai leysite, dehydrated Oickite 24.87 100+ (004) dickite 2Mj Chlorite 29 Range: 24.73 - 25.52 >nH with chlorite (see Table 2). 0HSQ1S90Z 347 -j.. /im n r ^ ^ r i n n / n d f SERPENTINE 1%KM),KXM).(OOI2) Ksssa KADLINITE dfloZ) HALLOYSITE c = 3 0ICKtTE d^cM) Figure 3 Peak nositions and relative intensities. The data of Table 3 are presented in graphical form to illustrate the variation in position and interfering overlap of XRD peaks of serpentine, kaolinite, halloysite, and dickite. tnsoimz http://legacy.library.ucsf.edu/tid/ump52d00/pdf V -- * CHLORITE dKxM) < = s K A O L I N I T E d(oo2i 1--- 1SERPENTINE deoa,coo,40012) HALLOYSITE d ^ , = > DICK ITE < W , I RELATIVE INTENSITY ZPISO90Z Figure 4. Peak positions and relative Intensities. The data of Tables 2 and 3 are presented combined. Illustrating the problems of XRO identification when chlorite and serpentine, and possibly kaollnlte, halloyslte, or dickite are also present. " ` http://legacy.library.ucsf.edu/tid/ump52d00/pdf age ft r-. , essoeniituiieoi> featuros --- d - o a a t TM . i" repie, e - 3. * " " 2 ' 3^' * . a_J_Ur% iHrtcif.iOII in 1. WIIJUU ^ w-w-. v-- . ..U_-w A^har 2. The chlorites sTM. serp.ht1.es orerlep and Interfere .1th each ether. a s j s interfere when present. The significance of that chlorite is a very common accessory miner is much less commonly associated. ^ 21" T S k j & isusss&itv'ss&s** .**-- Other Methods thfrere. Spectresc.py.qSI .ibeetlonal and hehdlhs asbestiform variety. nif*----iai Thermal Analysis (0TA1 .. . heat i S % ; er x gr A s \ i ^ S r r '^ 3 ^ ^ r u r = u . - - r : :si," s & X h ' * -- TM > ' " ' iss"^ i ; ? 8 355 i C b l ' S S l i U S l o t I t \ m area, .her.'asbestos . he ,1s1d>t1f1d. r r r i d f f i l i a . a T , " s. Sl.l.ar c m U other fibrous clay ,1n * 'i " isS S f " ' b e ' 'bestos, especially whee . ' M " - s a r s a s? & ~ * Select! are. alectron dlffracttor, i,; as aisphlbole. ^Mral microscope and decide on the basis of 9e is an amphiboH. T H * can * -- pattern P -- or c h w t " " I lta n . In the aeo<try whether or not the^partlcl since numerous ^ e r minerals c pattern geometry [10.111* Careful u r l l r " i ' S S S . 5 f S 5 S l p a t ................. 350 "-" r " 'a"'t ,,y " r j w.riu nn^r^^OHnn/nrlf 2063105143 of mineral which produced the pattern. Chemical composition is further required in order .to have a chance at Identifying the particular species when the mineral is a member of a complex group such as the amphiboles. Otherwise, misidentification will result. Cosmetic Talc Free from Asbestos In the United States, we have a self'regulating association known as the Cosmetic Toiletry and Fragrance Association. In certifying the purity of the talcs which they use, they are aware that no single method can identify asbestos and their most recent spec* ification for cosmetic talc [12] combines two methods (XRD and optical microscopy) for monitoring their types of talc. The rationale is that a talc is first examined by XRD, and if even the smallest amount of amphibole is indicated, then the test proceeds into optical microscopy using a dispersion staining technique to determine whether or not the material contains asbestiform particles in the amphibole group. Summary This paper has categorized the main methods which have been used for detection of asbestos in talcs. The basic principles of the various methods were categorized to explain how asbestos has been and can be misidentified in talc. Generally, misidentifications arise by jumping to a conclusion from a single mineral characteristic, when, in fact, many characteristics are required to fully identify a mineral species and/or its variety. Both optical microscopy and XRD required a more detailed review than other methods since they have received the most attention from a monitoring point of view. This review is presented with the hope that our guidelines will enable analysts to avoid the misidentification of asbestos in talcs. References [1] Ampian, S. C . , Asbestos minerals and their nonasbestos analogs. Mineral Fibers Session, Electron Microscopy of Microfibers Symposium, Penn State Univ., August, 1976. [2] Thompson, C. S . , Discussion of the mineralogy of industrial talcs. U.S. Bureau.of Mines Information Circular 8639, Proceedings of the Symposium on Talc, Washington, D.C., May 8, 1973. [3] National Bureau of Standards Staff, A report on the fiber content of eighty industrial talc samples obtained from, and using the procedures of, the Occupational Safety and Health Administration, 51 pp. (1977). [4] Bowndy, M. G., Gold, K., Burgers, W. A., and Dement, J. M . , Exposure to industrial talc in Vermont talc mines and mills: AIHA Conference presentation, May 1977. [5] Rohl, A. N . , Langer, A. M . , Selikoff, I. J . , Tordini, A., Klimentidi.s, R., Bowes, D. R., and Skinner, D. L., Consumer talcums and powders: mineral and chemical characteriza tion, Jour, of Toxicology and Environmental Health, 2, 255-284 (1976). [6] Rohl, A. N. and Langer, A. M., Identification and quantification of asbestos in talc, Environmental Health Perspectives, 9, 95-109 (1974). [7] Snider, D. W . , Pfeiffer, D. E . , and Maneuso, J. J., Asbestos form impurities in commercial talcum powders, Compass of Sigma Gamma Epsilon, 49, 65-67 (1972). [8] Scholl, R. and Drafts, R., 1977, XRD characterization of asbestiform reference minerals. Symposium on Electron Microscopy and X-Ray Applications to Environmental and Occupational Health Analyses, April 1977. 351 2063105144 .ucsf.edu/tid/ump52d00/pdf [9] Jenkins, R . , A review of x-ray diffraction procedures as related to the quantitative analysis of air particulates. Symposium on Electron Microscopy and X-Ray Applications to Environmental and Occupational Health Analyses, April 1977. CIO] Zoltai, T. and Stout*, J. H . , Comments on asbestiform and fibrous mineral fragments, relative to Reserve Mining Company taconite deposits: Report to Minnesota Pollution Control Agency, 89 pp. (1976). [11] Lee, R., Electron optical identification of particulates: Symposium on Electron Microscopy and X-Ray Applications to Environmental and Occupational Health Analyses, April 1977. [12] CTFA Specification - COSMETIC TALC Issued 10/7/76, The Cosmetic, Toiletry and Fragrance Association, Inc. Discussion A. WILEY: You said that instantaneous recognition of SAD patterns is difficult. Could you give some examples as to what kind of confusions could exist in this? Can you confuse amphibole with serpentine or amphibole with talc, or is that kind of a gross mistake possible? J. KRAUSE; Those kinds of mistakes probaBly would not generally happen if you are looking at pyroxenes or olivine. Electron diffraction is not one of my areas of real expertise, but I think that you could possibly get feldspars that would give confusing patterns, depending upon their orientation in the microscope. L. MADSEN: We are using all the methods that have been talked about today for identi fication for asbestos materials and do not in any way limit ourselves to fiber length and aspect ratios. J. WAGMAN: I would like to comment that it is possible by x-ray diffraction and through a special technique to identify and measure the presence of asbestos fibers even when they are in the presence of their non-fibrous counterparts. About two years ago this was demonstrated in a study which we supported at the Naval Research Laboratory in which samples were pre-treated so that fibers were first aligned and then the x-ray diffraction intensities measured at two different orientations with respect to the x-ray beam and 1n this way the intensity due to the non-fibrous counterparts could be subtracted from the total diffraction intensities. KRAUSE: You were putting the fibers in some specific preferred orientation in the sample and then looking for those orientations by XRD. WAGMAN: That is correct, and this had the advantage of not only making possible corrections, that is correcting for the non-fibrous material present, but also it greatly enhances the detectability for the fibers themselves. KRAUSE: Is this method being currently used? WAGMAN: This is a method whose feasibility was demonstrated and there are two publica tions on this in th literature. Actually our objective was to apply this method to airborne samples, which is a much more difficult application incidently, I should think than in the case of talc. The problem here is a preparative problem in that an air sample usually has a lot of organic material, sticky material present which interferes with the ability to orient the fibers. This is a preparative problem which Will have to be overcome. But I should think that in the case of talc samples you probably would not have that problem. 352 httD//leaacv.library.ucsf.edu/tid/ump52d00/pdf 2063105145 K. HEINRICH: the fibers? Would the talc plates interfere just as well with the orientation of WAGMAN: The orientation of the fibers is accomplished in an electric field, and the platy material does not preferentially orient itself. `HEINRICH: fibers. 1 mean, just in the sense of a passive restraint to the movement of the ' WAGMAN: This of course would have to be tested experimentally. A. LANGER: We heard today from a representative of one of the member organizations of the Cosmetic, Fragrance, and Toiletry Associations, that of 3800 consumer talcs . examined none contained chrysotile. Today you presented some interesting information on the identification of crocidolite in talc. Have you seen crocidollte 1n many talcs you have examined? " KRAUSE: No I have not seen it, nor did I say that I have. LANGER: It does not occur in consumer talcs, or is it industrial talc. not see why the crocidolite issue was raised; have you seen it? I just do KRAUSE: Just because I have not seen it certainly does not mean that it could not conceivably exist. All I was trying to do was point out that choosing a specific amphibole peak as being representative and definitive for giving a good identification of a particular amphibole species has great potential for error. There are many, many other minerals that could fall within that same two theta region. LANGER: I would agree with you that even though talcs occur in nature and they have great mineralogical variability they are still bound by the physical and chemical laws involving calcium-silicate rock systems. A mineral phase such as you described would not occur normally. wisomoz 353 .ucsf.edu/tid/ump52d00/pdf '