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Program Guide Identification of Asbestos Parts 1, 2, and 3

Date: 19830000/P
Length: 24 pages
87297145-87297168
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Author
Mccrone, W.C.
Type
SPCH, SPEECH/PRESENTATION
PUBL, OTHER PUBLICATION
Area
CRAVEN,BJ/LAB 11 ANALYT DEVEL
Alias
87297145/87297168
Site
G97
Named Person
Blanchette, J.
Bloss, F.D.
Chamot, E.M.
Deer
Delly, J.D.
Hartshorne, N.H.
Hatfield, R.
Howard, B.
Johnson, G.
Julian, Y.
Kist, O.
Mason, C.W.
Mccrone, L.B.
Mccrone, W.C.
Mesereau, A.E.
Palenik, D.
Palenik, M.
Prentice, J.
Stewart, I.
Stuart, A.
Taylor, D.
Teetsov, A.
Xxhowie
Zussman
Named Organization
Asbestos Mines of South Africa
Asbestos Particle Atlas
Brian Howard + Associates
Bureau of Mines
Cape Asbestos
Epa, Environmental Protection Agency
Fi Scott + Associates
Mccrone Associates
Mccrone Research Associates
Mccrone Research Inst
Microscope
Niosh, Natl Inst for Occupational Safety & Health
Ny State Dept of Health
Ann Arbor Science Publishers
Date Loaded
21 Jun 1999
Document File
87296828/87297250/Asbestos
Master ID
87297036/7249

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COLO, COLOR REPRODUCTIONS
MARG, MARGINALIA
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jyl99d00

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Page 1: jyl99d00
PROGRAM GUIDE i C Identification of Asbestos Parts 1,1 2',, and 31 Author WalterC. McCrone, Ph.D. D!i rector McCrone Research i Ilnstitute Ghicago', Illino!is. Program editor: Brian Howard, Ph.D: Guide editor: Anne B. Mlesereau: Narrator: G'ordonJbhnsorn Producer: Brian Howard andiAssociates; Ihc: Tabl e of Contcnits'. Prereqµisite'Skills ............................................ 3 Introduction ............................................... 3 Summary of the Program .................. .................. 3 Suggestions for Usiing the Program ............................. 3 Insthuctions for Fiunning,the Program .......................... 4 Script and I Programi Notes, ldentificatlon of! Asbestos; Part! 1` IdentificatYon' of Common Asbestiforrn'and'Nonasbestiform Minerals ................... 5 Script andl Programi Notes, Identification of Asbestos, ~ PartI2: ~ tdentificatiQn ~~ of'Q'~tfier~ Fibrous and Nonfibrou's Sample Components ................ 111 Script and' Program, Notes, Identification of A'sbestos, Part! 3: Practical' AnalXtical' TechniqWes .......... 18 ra.n^-•ma<,rn,.n,nrn>noe,a.,...> ...:.........r.~a.,.r.n~mr...,.~,,.,.n.~.~,an..++.n . . .. +..~.,.,....... .,...,.n. . . . .. . . a....-..:~+w...,~~.....~... .J"
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No part'of'this publicatilonimay bereprod'ucedl storedl in a retrieval system, or transmittW in any form or by any means, electhoni'c, mechanical, photocopying, re- cording, or otherwise, without the permission of' thee publisher. For information regarding permission, write to Briani Howard~ and Associates, lhc., P:O: Boz. 198, Brooklym„N'Y' 1i1202: ©1983,, Brian Howard and Associates, Jnc. ... ........... , ...... ...,........,.,... ... .. . . ...... ...,.,.....,.........,., ..., ,,. ,., , ~ .. • r•I ~ z.
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f Prerequisite Skills Before beginning this program you should have mastered the following prerequisite skilis: 1) Being abie to set up a microscope with proper FCf3hler illumination. 2) Being able to observe and interpret Becke lines, pieochroism„ matchingi wavelengths by dispersion staining, retardation, sign of elongation, and extinc- tioniangies.. If you idonot have all lofthesesk~ills, y, ou wil l not de-rive the maximum, benefit from this program. Miner- alogy courses offered in many colleges and univer- sities or the polarized light' microscopy courses of- fered by the M'c.Crone Research Institute willi provide this necessary background information. Introduction The name asbestos is used Ito describe a group of' fi- broushydrous mineral silicates which have important physical properties. These properties include high thermal stability, excellent tensile strength, chemical inert'ness, good thermal and electrical resistance, and the ability to, be subdivided into fibers. These desirr, aable properties led to the widespreadluse of asbestos in many different industries, and as a result it is now present~ im building insuiaRion, automobile brake lin- ings, and a wide variety of commercial and consumer goods. The most common asbestiform mineral is chrysotile, which accounts for about 90% of the world-wide production. Most ofi'the remaining 10% is eitheramosite or crocidolite. ~ Regarded iiniti'ally as one of' nature's blessings, asbestos use increased rapidly during, the eariyyears of this century. Hbwevers evidence gradually accumu- lated which, indicated that asbestos was a, serious health hazard~ and the Environmental Protection Agency(EPA) is currently assessing the disease:-caus- ing potentiall of intermittent low-level exposures to asbestos-containing materials that can occur inibuild- ings, especiially school buildings. The cost of' clean- ing up the nation's schools and all'the otherbuiidings that contain asbestosinsulk tion is; of' course, a monu- mental problem inI terms of' it's cost and complexity. Sometimes, removal of the asbestos-containing mate- rials actually increases the health hazard, in which, case some type of' encapsulation or isoiation proce- dure is adlrisabie. EachI situation, has to be considered' separately. But the first task is always to get reliable informationi on the composition of the suspected asbestos-containing material. Ideally these questions should be answered: 1), What asbestiform substances are present inithe sample? 2), I'n what proportions are the asbestiform sub- stances present? 3) Whatottier substances are present?' 4) What are the particie-size ranges for each com+ ponent of the sampie?'. In recent years, M'cCrone Associates„ Inc. in Chi+ cago and McCrone Research, Associates Ltd. in Lon- don, have anaiyzedl many thousands of' samples of ~ insulation and other possible asbestos-containing ~ materials and have provided definitive answers to the above questions. These analyses have been the basic information on which ciean-up plans havebeen based. 3 The proven methods used by McCrone Associates are being taught by Dr. Walter C. McCrone of' tihe Mo- Crone Research Institute: To facilitate the learning of' these techniques, this audiovisuall program was writ- ten by Dr. M'c.Crone based onithe techniques that are taught in his courses onithe identification of asbes- tos. The analytical method advocated by the author is poiarized! light microscopy because only this tech- nique allows complete and, for the trained~ microsco- pist, rapid identification of' the various possible com- ponents of asbestos-containing materiais. Summary of'the Program The program is divided into three parts: Part 1i cov- ers the identification of common asbestiform andl nonasbestiform minerals. The crystal lography and thee dispersion staining curves of these minerals are dis• cussed and the appearances of, samples of'each typee of mineral are shown, by a selection of slides from Dr. MbCrone"s extensive eollection, Part 2'covers the identification of other mineral and nonmineral components that may be presenti in a sam+ pie. The author stresses that the microscopist should always aim for a complete analysis ofiall components in a sample. This safeg,uards against a possibly harm+ ful component slipping by as an unidentified com+ ponent. The microscopical techniques used ini this . part are the same as those usedlin Parf 1. In the third part of the program+ Practical analytical Techniques, Dr. M'cCrone describes how to proceed with the analysis of' reall samples. A f'low, chart gives guidelines for the systematic analysis of'the sample. However,, the author gives the trainee the benefK of his considerable experience by explaining a number of time-saving tips for the anaiysi's of certain kinds of samples. This part of' the program concludes with ani examination of several standard insulation samples preparing, the viewer for his or her first "reaii" samples. The script and supplementary notes are printed ini the Program Guide. The supplementary notes are printed in bold-face type and'follow the portion,of'the narration to which they relate. The supplementaryy notes give important additionall information that will be helpful to those performing microscopical anal- yses of' asbestos sampies. Suggestions for Using the Program This program describes the techniques usedlbyDrL WaiterC, M'cCrone andlhis colleagues at the McCrone Research Institute for the identification, of' asbestos and other minerals that may be present in samples suspected of containing asbestos. The program was written by Dr. M'cCrone to follow, cioseiy the material presented in his short courses onithe identification of asbestos and provides a comprehensive and l authorr, itative treatment of'the subject. To meet the needs of all types of, training situations, the program may be used either for, individual study or as part of' a training course given by an instructor. Individuals (or small groups) may run the program without the participation of' an instructor or supervisor. The individual viewer may control the pace of the programa repeating, parts whenever necessary to improve understandiingi It is suggested that the narration printed in the Program Guide be followed whiie viewing the program. The
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4 tape may be stopped after those frames which are fol- lowed by a note (printed ini bold-face type), andl the note may be read'before continuing with the program. Instructors giving training courses on the identi~ fication of asbestos will find the program an, invalu- abie f'ramework for a thorough discussion of'the sub. ject. Dr. M'ct;rone piannedi the program to cover the subject in a logical iand i understandable mannen Each instructor has his or her own specific needs which ean, be easily incorporated into the flexible siide- aud'iotape format. The presentation, should be con+ trolled by tlhe instructor and may be stopped at any point to enable the Instructor to add his or her own comments. Samples of' special interest may be dis, cussed by incorporating, some additionall slides into the program: Such a presentation combines the at- tractive features of an audiovisual program with thee motivation provided by an instructor. All instrructorss planning to use the programiare advisedlto review, it carefully before use. The more familiar the material is to the instructor, the more effective it willibe as part of a training course. Instructions for Running the Program A 35-mm slide projector and a cassette player are needed to run tlhe program. Be sure that' bothi are ini good workingi order to avoid damage to thecom-ponents: Eachipart of'the program consists of aiset of slides and a.cassette: The three parts of the program. were designed to be run in sequence. To run each part„advance the siides to the first frame; each, frame is numbered' in the lower raght corner and also on the slide mount. Be sure that the tape is fully rewound be- fore starting the narration, which willllbegin atthe title frame. There is a pause in the narration, between frames t'o allow time for frame advance. Following the narration im the Program Guide will ensure synchro- nization, but an additional'reminder, is the announce- ment ofithe frame number onithe audiotape before the correspondingi segment of' the narrationi When you hear the announcement, check the number in the low•, er right corner to be sure the right slide is being pro- jected. It is recommended that the program be stopped wherever appropriate so that the suppie+ mentary notes may be read. Please note that the audiocassettes are recorded onn both sides, with approximately half the narration on each side. Be sure to start the narration on the side marked "Side 1." When the fi'rst side has beenipiayed; flip the cassette to continue the program. Guarantee The slides and cassettes In this program, are guaramtieed'against'operating defects.. Iti'any of'these components proves toibe detect'ive„pllease return Kto the distrti utor, F:IL Scott and Associates, P.O. Box 66j, Route 1, Check,ltA 24072, , for replace- mentL .......... ....... _ . . _ ......... . ......... 11, .. . _.. . ... .. . .... ... ,... . _ . . ...... .. .. ......,........._. , Z„2,nrn . . ....... ........ J9J1a
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Script and Program Nlotes ID'ENTI FIICATIO'N 1O F ASB ESTOS' Part 1i 1. Practical Microscopy. ldenlff'ication of'Asbestoso Part' 1: ldenti'fication of Common Asbestiform and Nonasbestiform Minerals. 2. Amosite is a common example of' an asbestos mineral. Asbestos minerals are a group of fibrous sili- cates characterized by unique physical properties whichiiinclud'e high thermal stability, excellent tensile strength, resistance to chemicallattack; good thermal andleiectrical resistance, and the ability to be subdi'F vided into fine fibers. 3. These special qualities are responsible for the widespread use of asbestos. It has beeniwidely used as building insulation, as roofing and flooring, and as reinforcing additions to cements, mortars, andlother coatings. Another important use of asbestos has been iniautomobiie brake linings. More than 3,p00 individ- uall uses for asbestos have been reportedL Wnt'iI very recently, asbest'os and asbestos products were pro~ duced and used throughout the world withourt'any re• gard f'or„or, knowledge of, possible adverse heaithief- fects. 4. These asbestos "bodies" (also called "ferrugi- nous bodies") were removedlfrom a human lungidurr, ing the autopsy of a patient who died from asbestosi's. In recent years, industrial health professionals and ~ the public have become increasingly aware of'the ear, cinogenic potential' of asbestos. As a result, NIOSH has set limits on the concentration of asbestos fibers inithe air inside industrial plants, thus greatiy reduc- ing the hazard to workers. The EPA has also eneour, aged efforts to assess and eliminate health hazards to the general public outsid'e the work place. 5. Until recently,"the majorieffort has been concenr trated on public schools, but other public buildings are now drawing attention. Eventually, all sources ofl potential health hazard's due to asbestos are certainito be evaluated. 6. At this time, a concerted ef'fort'is being made to remove active and potential sources of' asbestos in the environmentL To assist in, this operation, it is es- sential to have dependable methods for the evaluation ofiasbest'os sources. Good'sampiing methods are the first necessity, but dependable methods of identiify- ing asbestos and measurement of the degree of'haz- ard for each source are equally important. 7. This program deals with the identification prob- lem by answering these three questions: Are fibers present? Are they asbestos? What other substances are present? & The only analytical technique that provides tihe answers to all of'these questions is polarized light mit croscopy. In a, few minutes, a trained microscopist 4L like Yvonne Julian, shown here at McCrone Associ- ates, can give dependabie answers to each of the three preeeding questions. 5 In dealing, with i'nsullation samples, we are not analyzing i homogeneous products. Methods of' mixing and application on site make i't i'mpos- sibte for the analyst tio obtain ia truly representa-, tive sampie: Thus accurate quantitation (as achievedlby XRD) Is only representative of'the laboratory samplle and not of the Insulatilom Ad- ditionally, because of'uneven mizing6, a trace of' asbestos In ai laboratory sample could' Indicate much more asbestos present elsewhere Im the i'msulatiiom. Thus high sensitivity Is reqwl'red. ©niy the use of' the sterecmicroscope ln con- junction with polarized light microscopy (PLM) enables a large laboratory, sample to be com- pieteiy surveyed and' the different filber types rapid'iy identified. The fiber size d'istribution, in, alll commerclally, supplied asbestos grades al-, lows a reasonable percentage to be visible at low magnifications using the stereomicroscope. The llar9e field' of' view ensures good sensitivity durting the scan. Hand~picked fibers from the stereomicroscope sample are most rapidly iden. tified I by PLM. Although other techniqiues, such, as x-ray diffraction„ imflrared absorption, and electron microscopy, can be used to perform, the analysis after the stereomicroscope examina- tion, the cost In, time and equipment Is exorbi- tanrt compared with a 5-minute-or-less mounting time and inspection usiingithe P'LM. The use of'sophisti'cated equipment such as XRD,1R; and electron microscopy for analysis of insulation: 1), lacks sensitivity, 2) Is using a sledgehammer to crack nuts, and' 3)I puts un- necessary expense on the client as well as Incur- ring,needtess time delays. 9. The objective of'this program i's to enable you to identify, by polarized light microscopy, asbestos min+ erais and their substitutes in, any type of' sample; for example, Insulation, atmospheric dust,, and taic prod~ ucts. For some samples Ilike lung tissue, water, and otherflluids, the transmission electron microscope is necessary iniorderto see the finest fibers:. To benefit' fully from this programi you should al: ready be a trained microscopi'st familliarwith, optical crystallography including dispersion staining. The prerequisite skills Include being i able too set up a microscope with proper iCtthiler illiumllna- tion„ and being able to observe and interpret' Becke lines, pieochroism,, matching wave- lengths by dispersion staining, retardation, signi of elomgation~, and extinction angles. Mllneralogy, courses offered in many colleges and univer- sities or the polarized li'glht microscopy courses, offered by the McCrone Research, Insti'tute witl, furnish, this necessary background. Also vseful are the following itexts: 1. Btoss, F.M, An Introduction to the M'ethodss of Optical'Crystallograpny, Holt, Rihehaft & Winston, NewTork (1961): 2. C'hamot, E.M'. and Mason„C.N{0., Handbook of' Chemical' Microscopy, vol. 1, 3rd ad., , 1Mliley, N ew York (1959). 3. H'art'shorne, N1HI. and Stuart, A., Crystals: and the Polarizing Microscope, 4th ed,,. Arnold, London, (1970).
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6 4. Hartshorne,, N.H., and Stuart, A., Practical' Op:tical'Crystallography, 2nd ed.,, Arnold'4 London,(1i969). 5. McCrone, W:C., McCrone, L.B., and Deily;, J.D., PolarizedLiglitMllcroscopy, Ann~ Arbor Science Publishers, Ann Arbory: Mich. (1978). 6. McCrone;, W:CDeliy,, J.C'. ei al., Particle Atlas, 2nd ed.,, volls: 1-6y Ann Arbor Sci- ence Publishers, Ann Arbor, M'ich. (11973-11980)L 7. McCrtone„ W:CL, Asbestos Particle Atlas, Ann Arbor Science Publishers, Ann Ar-, bor, Mich. (1980): 10. We'll begin with detaills of asbestos terminol: ogy. There are a number of minerals that crystallize in either a fibrous or nonfibrous form. Only the fibrous forms are called asbestos, and these are knovvnias as- bestiform minerals. This table gives the names of the asbestiformimi'nerais you may encounter and the cor- responding nonasbestiformimineral names.. The opticallandlothercrystallographic proper- tles of the fibrous and nonfibrous forms of' a given mineral lare substantially id'enticali For ex+ ample, fibrous tremolite andl nonfilbrous tremo+ lite show the same refractive i'ndices and by x- ray diffraction reveal the same lattice spacings. As shown here, some fibrous forms of aigilven mineral have a special name while others are simply called fibrous ornonffbrous forms ofl that' mineral. Chrysotile; the only serpentine asbestos, is a layer-like molecular structure which can crystal- lize either as fibers called chrysotlile, plate-like crystals called lizardite, or rod-like crystals called antigorite. The latter two, are polymorphic forms of, chrysotile with closely, ssimilar struc- tUres: The other asbestos minerals are alll chain- like silicate structures ciassifi'ed!as amphiboles. When, asbestiform, some of these have speciali names such, as amosite and Icrocidoliite. Amosiite„a name adapted from an, acronym for Asbestos Mines of' South Africa„ is the fibrouss form of the minerals cummingfonite or gru- nerite. Commerci'ally, mmined amosilte is nearly al- ways fibrous grunerite. Even when, the iron con- tentl of the amosite is: less than 70%, it ls usually replaced by manganese and stilll contains less than 30% magnesium, so it has allways beeni termed gnunerite. Crocidolite is the fibrous form of the mineral riebeckite. High magnesfum, riebeckites are termed magnesioriebeckites; at! least~ one such has~ been ~commercially, mined ini B!ofivia and: sold as croci'dolite. The other amphiboles, tremolilte„ actinolite, ferroactinolite, and' anthophyllite, can be either fibrous or nonfibrous, but have no special names when asbestiifl 11i. Here are the chemical formulas oPcommon asr bestiform and nonasbestiform minerals. All of these asbestiform minerals are sillicates andl all contain magnesium. The serpentine chrysotile, withiits nonas, bestiform polymorphs, lizardite, and antigorite, are simply magnesium silicate. The amphiboles all cont tain other cations iin addition to magnesium. The tremolite amphi'bole series minerafs, conr sisting, of tremolilte i'tself'and'actinolitle,, contain calciumi In additfon t'o magmesium, and ilrorn There is a thihd' tremolite series of amphibole called ferroactinolite. Although, not at all comr mon,, itl contains higher percentages of' ilron along with calcfum, and magnesiuml These three minerals form i a i continuous series of' solid solutions having compositions ranging from, 01 to, 100% iron as the magneslum, bei'ng i replaced by iron decreases correspond- ing,Iy from 100! to 0%. Anthophyllite„ containing only magnesium, and Iron; as the silicate, can, also vary iln com-, position as iron replaces magnesium. The two asbestos-type minerals cummingtonilte andlgru-, nerite (called amosite when fibrous) ai'so, form a third continuous series of'solid!soluti'ons rang- ing from complete absence of lron In Iow-refrac-, tive-index cummingtonite to complete replace- ment of' the magnesium by i'ron, in the high- ref!ractive-index grunerites: Crocidollite, the fi- brous form of the nonf'ibrous mi'nerallriebeckite, is the only asbestos mineral containing sti ometlric amounts of sodiumi and it too can vary in iron content. Fortunately, despite tlhe potential vartiatiion in physicall properties and composition within the asbestos series„ tlhe relati'vely, few commerci'al' mine sources generally represent fairly constant chemical composition. For this reason, the mi- croscopicall properties do not vary nearly as much as might be expected. 12. The three serpentines, asbestiformi chrysotile, plate-like lizardite, and rod-like antigorite, have thee lowest refractive indices of any of the asbestos mint erals, averaging around 1.550. They are easily differ- entiated from the amphiboles, whose indices all lie above 1.60. Electron microscopy has shown chrysotile to be a scroll4ike layer structure. In other words„ the layers have been rolled into fibers and the optical properties are therefore somewhat~ un-, usual. We have chosen to represent them as: shown here with, the high refractive i'ndex paral- Ilel to the length and a combination of a and p ini the crosswise dfirectiom They dos in general„ show parallel extinction„and Iwe distinguish two: dispersion, stailningi colors, one for the cross-, wise vibration direction and the other for the. lengthwise direction. Although strictly speaking i i'tl is a monoclinic crystal+ chrysotiile behaves as though i'i is unisxi'aI with parallel extinction. The refractive Indices of' lizardite are not very, ddifferent f'rom; those of chrysotile., However, thw usual plate-like view shows the two hilglhi refrac- tive indices„ /i'and y. The matching wavelength A« , i'n the conventional 1.550 0 identification liqpid is about the same as that'for the lengthwise index of' chrysotile. Lizardite plates on edge will show the same xi color, parallel to, the length of' tlhe more fibrous-appearing edge views. But, the C, + •:;a!{fii
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! crosswise direction on the edge view willl show a higher Ae (blue or pale b!lue)icorrespond'ing to, a. Antigorite normally shows higher refractive in- dices and i's rod4like. It has three refractive in- dices, a, p,, and y. The colorsJn, 1.550 are usually alll In the golden-yellow.to•magenrta range. O!ften these tlwo polymorphs of chrysotile are encoun- tered d'uring microscopicall examination, of ai sample before chrysotille is observedl iilowever,, their presence In any sample probabil7 ensures the presence of chrysotlile.. 13. Here we see the dispersion staining i curves for chrysotile. They are piottedl in the usual! unique dis- persion staining, manner with the refractive indices of' the various Cargille liqqids at 589 nm plotted as a flat horizontal l lline with the matching wavelength xoi as the abscissa. These curves (one for the parallel vibration direction and one for the perpendieuiar) show the re- fractive indices of the Cargille iiquids having the same refractive index as that of chrysotille at eachi of'the wavelengths in the visible range. Chrysotile could be identifiedl ini any ofithese iiquids In the no range fnomi 1'.530 to about1.560L However, it is most convenient1o choose Cargille high dispersion liquid no = 1.550 ass the standardl liquid. Iln this liquid, the two matching, wavelengths, ilndicated by arrows, are jjust und'er 500' nm for y parallell to the length and just above 600' nm for the perpendicular a-P dirsetion. It1s important to remember that not alllifibers of' chrysotile will show precisely these matlching, wavelengths In thils liquid. The composition of' i~ chrysotille can, vary siightly due to the presence of' ilmpurtity elements and to weatherting,.. The birefringence willl very generally be close to 0.007 flor alll crystals of chrysotile, but the ac- tual lindices themselees can move to9etherup, or d'own, depending on, the precise combination. Matchi'ng,wavelengths as low as 450 nmiIlength- wise and 1650 nm crosswise have been observed I for weathered chrysotile fiben:, and as high, as 610 nmi and 700 nm respectliveljl forchrysotille from different mllnes. Despite this variations the identification, ofl chrysotile by dispersion, stain- ing! is still dependable, since no other asbesti- f'orm i minerall shows refractive index colors any- where nearthese values in the 11.5501Iliqui'd. 14. This and the following five photomicrographs show typical chrysotile fiibers mounted in the recom- mended standard 1i.550'hi'gh dispersion, Cargille liquid using several appropriate polarized light microscopy techniques: First, we see the sample with ordinary polarized light with an east«west poiarizervibration d'i- rectiioni Note that even thoughithe refractive indices of, the fibers are almost matched by this liquid, the fiber edges show definite colors. These same colors will be seen more distinetiy in the next frame. 15. Here is the same field of view using the annular stop dispersion staining objective. The greencoior, for the lengthwise or parallei'vibration direction ind'icates ~ that the Cargiile liquid andlthe fiber have the same re+ fractive index in the green, corresponding to aiwave- length of about 530 nm. The orange colorinthe cross- wise or perpendicular direction, on the other hand, in+ dicates a match, inirefractive index of liquid and fiber 7 at about 630 nm. Note that the resolution of' image detail l is not~neariy as good as a 0.25 NA 1iOJ( objective usually gives. This is because we have reduced its NA to about 0.05 with, the annular stop. Remember, we are trying, to resolve colors, not Image detail. 16. These are the complementary centrall stop colors for the same field of view;, magentai corre- sponds to the lengthwise g,reen by annuiar stop dis- persion stai'ning„and'the deepibiue of the crosswise direction corresponds to the orange observed with the annu iar stop.. Since the colors are more easily observed with, the central stop; and I the contrast is much better, we generally use the centrall stop for identi'fi'cation of chrysotile. Note that the very fine fi'bers seen here with tlheir distinctive coibrs by central stop, were Invisible withi the annular stop~ Therefore„i'n general much finer fibrills and much, finer particles are visible when, using the central stop6 17. ©ftenithe fibers of samplles under investigation for asbestos are almost completely covered with smallerpartieies of cement ormortar. This makes ital- most impossible to see the individ'ual fibers and to distinguish the dispersion staining, colors. In such cases, crossedl polars should be used. Here we see the same field of view as showni in the precedingi frames III rotated 45° into the brightness positioni with crossed poiars. The polarization colors withi these fibers are all in the lowerf'irst order but depend, of course, onithe thickness of the individualibundles: Crossed polars will oflten, show the presence ofl continuous birefringent fibers under or cov ered by other extraneous substances. Examples ofl this siltuation, referredlto as the "'Miiky MVay" ef'fect are discussed'in i Part 3'of i this program. 18. The first-order red (or red I) compensator, may then be inserted to determine the signiof eiongation.. Here we see that with the vibration direction of, the slow component for the compensator from, lowerieft to upper right, the fibers show a positive sign ofieion- gation characteristic of chrysotiile fibers. AIthoughi only crocidolite of, the asbestos fiber, family shows a negative sign of eiongation, there are other fiibers of asbestiform appearance which may have ai negative sign, of elongation, e.g,,, wollastonite and brucite. Therefore, when, the refractlive Index data are equivocal, this test, using the first-order red plate, should' be per-, formed' to help, eliminate these other posslbil- ities. 19. . A microscoll often examines particulate sam- ples with slightly uncrossed polars to be able to see and distinguish between isotropic and anisotropic particles. Here chrysotiie asbestos Is shown with the polars uncrossed about 15°. The polarization colors are not very different from those seen earlier with compieteiy crossed polars, but any glass fibers or other isotropic substances present could now be eas-, iiy seen against the gray background.
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8 20. Samples containing asbestos often contain several other kiinds of fibrous material„ and we may use other refractive index liquids to identify such components. For this reason„ we should be familiar with the appearance of'chrysotiie in these other liq- uids. Ih either standard liquid 1.605 or 1.680, chry,soa tiife will show good contrast, andj aithough Ao is greater thani 700, nm, the dispersion staining coiorss will' be a definite pale blue withi the eent'rai stop ini both liquids. Accordingly, this indicates that the re- fractive indices of the fibers are lower, than that of'the liquid inwhich they are mounted. 21. All three tremollite amphiboie minerals have the same monoclinic structure, but they vary in composi'F tion and optical properties. The relationship between their refractive indices and composition is shown here. Tremolite contains up to,20%o iron repiacingian equivalent amount of' magnesium, and its refractive indices are lower than those of either of the two other minerals in the soiid'sollution series. Actinolite shows from 20% to 80% iron (again with iron replacing ann equivalent amount of' magnesium)j Finally, ferroacti- nolite has the highest refractive indices, and contains in excess of'80% iron and less than 20% magnesium: 22. Here the crystallography of, the three minerals is summarizedl In the maximum oblique extinction view, the two ref'ractive indices for all three minerals are a and y. (i'and y' are shown inithe parallel extinc• tion viiew. The biref'rting$nce of'these minerals is higher than that of chrysotille or crocidolite butl lower than that of' anthophlrllit'e. The extinction angie varies continuously through the t'remollite seriess with, the highest value for tremolite it'self' (1i9!-21 °) andi the Imwest' for ferroactinollite (1i0!-15°). These vallues are characteristic of the nonfibrous habits. Fibrous trtemoiiite (as well as the other amphiboies) has much smalierextinc-, tibnianglles. In studying any of these minerals, the a-y, ori~ entation is located by looking for the crystals that shmw the largest oblique extinction angle. The /3 refractive i'nd'ex di'rection, is located as the crosswise index on, the view showing parallell ex- tinction. 23: The dispersion staining curves for tremolite shown here are representative of'nearl'y ali'of the sam- ples of tremolite we have observedl either in the fi- brous or nonfibrous forms. The obvious standard liquidlto use for the identification of tremolite is 1.605 because it intersects the dispersion staining curves for a„/f, and y within the visible range. In the Cargilile 1.605 high dispersion liquid with the annular stop, you can expect to see a, yellow-orange with Ao about 680, nm for a on the oblique extinction view. The y direc- tion will show a, biwe (about 427 nm) on the same oblique extinction view. The (f crosswise direction, on the parallel extinction view will show a green, of'about' 530 nm. 24. Crystals of nonfibrous tremolite mounted in 1.605 high dispersion liquid showing various orienta tions appear in this frame viewed with the annular stop. The green crystallin the lower center is oriented' to show aniindex ciose to p. The small y,elllowcrystal j;ust, left of' center is oriented to show the a low index direction, and the biue crystaVs are all oriented ciose to the yorientatiom 25: Using the central stop shows the correspond'~ ing complementary cofors, The biue y-oriented crys- tais seen in thepreceding frame with the annular stop are now, yyellow, whereas the green p orientations are now magenta, and! the yellow a orientations are pre, dominantiy blue. 26. The crossed' pofars view shows moderate re- tardation corresponding to the relatively high birefriin- gence for this particular asbestos mineral. The long- biaded crystal showing, high first-order colors in the lower left would be at' extinction if this were the (f-y' view. Since it is obviously not at extinction this must correspond to the a-y view. 27. The positive sign,of elongation is shown inthis photomicrograph, taken with crossed polars and the first-order red plate. The long blade, left of center, shows complete canceilation of, the original first- order red colors andl indicates the high refractive in- dex direction Is parallel to the length of, this crystal. This eorrespond's to the y or y' directiiondepending on the rotation about'iits length. 28. We now see tremoiite mounted inCargille 1L550. high dispersion liquid, butwith theannufardispersioni staining, stop. Dispersion staining colors are more easily visible with the central stop when the matchiingi wavelength is in the visibie„ but the colors are more easily visible withi the annular stop when aa is muchi higher than 700 nm or lower than 400, nm. Here for exampie, in, 1.550, tremoiite shows distinct dark biue borders corresponding toia high-refractive-iindex parti- cie iniailower-ind'ex liquid. 29. Here is a, similar sample of tremolite in 1.680, Cargiile liquid with the annular stop. Now the edge colors are yellow-brown corresponding, to a lower- ref'ractive-index particle in a high-refractive-index liq, uid.. 30: Now we turn our attention to the fibrous form of' tremolite; i'n other words, asbestiform tremolite. These crystals have essentially the same refractive in~ dices as those of the nonfibrous mineral. However, because:theyarevery,fine, itis moredifficuite to orient them to show the individual /i and a crosswise index direction and to determine the extinction angle. Nor, mallythen we refer to the lengthwise xa and'to anaver, age crosswise abicoion In this„the first frame in this series, we see tremoiite mounted in 1.605 high disperr sioniliquid'with the annular stop. The lengthwise coior is blue, and in the crosswise direction the cofor is yel- low with, hints of' yeI low-greem In, flact,, a recent' careful study of a fibrous tre-, mollite showed lamellar twinning similar to thatl discussed later for amosite (Frame 51). If this turns out4o be generally true, fibrous tremoiite,; like amosito, will behave as an orthorhombic (
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C rather than a monociinic crystalL We will see as we proceedlthat anthophyllite is orthorhombic while all of' the other amphi- boles are monoclinic. We would 'normally de- pend on the iatlter to show oblique extinction In some views, whereas anthophyllite should al- ways show parallell extinction. Unfortunateljr,, the monoclinic amphiboles can, when fi'brous„ show Ilamellar twinning on the 100 twin piane wi'th the result that the normally oblique extinc- tiiow views show parallel extinction or a very small angle of C5 °. This causes trouble onlywilth the differentiation i of anthophyllilte from tremo. lite because both show quite similar refractive indilces with their y indices parallel to the fiber length. So, what canwe do aboutlt? fdlot everyone has a i micrtoprobe to 1 look for the calcium present in tremolilte but not In i anthophyllilte. Fortunately, howevery even, when fibrous the percentage of' right and~ left extinction orientatli'ons may not! be exactly, the same, especiially in, very fine fibers, and ini t'hose cases small oblique extinction, angles In, the 1-5 °' range can be observed~ for tre-, molirte. We can, check this by looking for the Q.r orientation, by the dispersion staining i colors in 1.6051'iq,uid'4 i.e:,, yellow and blue. These crystals are oriented so that they wouW give oblique ex•, tinction, i'f they were not'twinnedL If, the balance i'snot 50150, these fibers willlshowslight oblique extlinction. We might alsolook for stralghrt~ stiff, and less fibrous crystals within the samplee which show oblique extlinctiom The samples off fibrous tremolite examined by the author have all i shown a few very small, straight, stilff' rods showingl oblique extinction of1 15-201a. The ab+ sence of oblique extinetion, on any of'the crys• tals oriented inithe yel'low-blue d!ispersi'onst'ain- ing orientatiion should indilaate anthophyllite. lfou must,, ofl course, be certain, that your, polars are exactly crossed~ and'that the vibration directions of the polars are exactlyy parallel to the cross lines. The author checks this by usimgg bright nyion, fibers (fft2 In the MbCrone Associ'F ates prepared slide set) since t'hey are strictlyy parallel lextinction.lf'that adjustment is careefuliy made, then variations ofi even, 1la or 2°' In extinc.tioni cani be detected, and this should be enough, to di'fferentiate fibrous tremolite from fibrous an-, thophylllite. One other point i's that ifi the asbes., tos i's not so fibrous but shows straight and stiff' rods or needles, then, parallel extinction willl cer, tai'nly i'ndicate anthophyllite because any tremo- lilte or amosite with, that crystal habit would show higher extinction angles. 31. Since the blue and yellow annular stop coiors are complementary colors, the central stop dispersion staining colors shown here are the reverse of, the an- nular stop colors just shown. The goidenryeilow is now parallel to the length with blue crosswise. 32: Here the field of'view has been rotated 45° to show the polarization colors with icrossed ipoiars. 33: The retardation is relatively high for fibers of. 9 this thickness, and the fieid of view with crossed~ polars and the fi'rst-order red piate shows a positive signiof' elongation, as it should foraif tremolite-seriess asbestos. 34'. The dispersion stainingi data for actinolite are shown here. Although actinolit!e is rarely found In in- sulation samples, it'Is not an uncommon mineral, andl it is often asbestiform. Actinolite shows slightlylower birefringence, but slightly higher refraetive indices than those of tremolite. 35. Here we see nonfibrous actinolite ini 1.605 Iiq. uid with the annuiarstop. The colors range from blue- green for a to dark blue forthe y orientation 36. Corresponding complementary eentral stop colors in the same 1.605 liquid~ are seen here to be golden-magenta and pale yellow for low and' high inr dex directions, respectively. 37. This is the same preparation rotatedA5" viewed with crossed polars. The retardation, is fairly high, and the sign of elongation is positive, as with all tremolite series milnerais. 38. The positive sign is determined by the first- ord'erred plate with crossed polars shown here. Addi- tion of retardation occurs for those elongated crystals orientedi lower left, upper right„ and subtraction oc- curs for crystais oriented lower right, upper left. Actinolite i's q,uiite easily identified In the 1.605 high dispersion liquW normally used for tremo- lite: The exti'ncti'on, birefringence, and shape are all similar to the corresponding propertties of'tlre- mollite: However, A6 for each of the three direc- tions In actlinollite is lower than the correspomd- ing k& for tremollite, and the colors are alil dis- pl'aced toward the blue or the green with the an- nular stop„ and I toward the yellow and golden magenta with the central stop~ 39. In 1.550 high dispersion liqµid, actinolite shows essentially the same, but darker4 blue borders, as does tremoiite in the same liquid. 40. Here we see actinolite mounted in 1.680 liquid but with the central stop: Since the refractive indices of'actinoiite are lowerlhan 1.680, we should expect ka, to, be considerably higher than 700' nm. For this rea- son, the dispersion staining colors are pale blue with the central stop. They would, of course, be dark red- brown with the annular stop. 4'1'. Now let's turn to the crystallography of antho- phyilite: Althoughichrysotile, amosite, and crocidolite are by far the most common commercial asbestiform, fibers, anthophyllite is not uncommon and must be diff'erentiatedl particularly from tremolite since its lin- dices usually fall' im the same range. Dif'ferenti'ation, however, is usually easiiy made basedonidiff'erenees in extinction. Anthophyllite is orthorhombic and' shows only parallel extinction, whereas alllof the tre- molite series crystals usually show at least sliightiy oblique extinction in some orientations. Anthophyllitee shows y orientation parallel to the length of the fibers,
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hence it' has the same sign of, elongation, as do thee tremolite minerals. If fibrous, the t'remoiite series of, crystals may show lamelllar twinning like amosite and also therefore parallef extinctimm In this case tremo- lite (or actinoii'te) and anthophyllite are very diffli+ cult to diflferenti'atle. Usually, however, some of, the tremoiite fibers will show at' least sii'gfhtfy, ('1i-5 °)iobiiqNe extinction. Anthmphylii'te does show a very wid'e range of, refractive indi'ces depending on i'ron conrtent,t but most of'the samples we have ever observed show muchlower indices than those of amosite. 42. The dispersion staining data for a typical'antho- phyllite asbestos are shown here. Ini1.605'hig,h disper-sion Cargille liquid, xa for y is about 400 nm; for, about4'60 nm; and fora, about 6001nm, 43. Here we see fibrous anthophyllite in Cargil'le 1.605 high dispersion liquid wi'th the annular stop. The colors are blue (approxirnately400 nm) parallel to the length corresponding to y, and blue-green (approx- imately 500 nm)i crosswise, corresponding to a and pP together. 44. The corresponding view with the central stop shows the complementary yellow parallei to thee length and golden-yeilowcrosswise. 45. Here anthophyllite viewed with crossed polars, shows low first-order polarization colors. 46. The positive sign of' elongation using the first- order red plate is indicated by the blue for the fibers running, lower left to upper right parallel to the slow component direction of' the compensator, and yellow in#he opposite direction. 47. Anrthophyliite i'n the 1.550 highidispersion liquid with the annular stop appears with dark biue borders characteristic of afiigh index fiber in a lowerref'ractive index Iiquid. They would be alpaie yellow with the cen- tral stop. 48. Conversely, when mounted in 1.680 we see the central stop colors are pale blue. Now, they would be yellow with the annularstop: 49. Next we turn to, the amosite solid solution series of' two minerals, cummingtonite and grunerite. Both milnerals have the same structure, varying, only in the refative percentages of iron and magnesium, The variation of' refractive index with composition is shown here. Cummingtonite is the loweriron+content mineral withicorrespondingiy lower refractive indices. Grunerite contains more than 70% ilroni and less than, 30% magnesium~ The refractive indices, of' course, rise as iron replaces magnesium; and are consid'erablyy higher than those of' any of' the other asbestos types except occasionally anthophyllite or ferroactinolite.. (These latter two minerals are relatively uncommom,)i Amosite is second only to chrysotile in,it's frequency of appearance in commereial asbestos products. 50: The crystallography and optical propert'ies of' cummingtonite and grunerite are shown here. Note the range of'refractive indices, extinction angles, and, optic axiali angles for these minerals. Most' commer-, ciali samples of' amosite seem to fall close to the bor, derline between cummingtonite and grunerite. 51. Although cummingtonite and grunerite are monoclinic, the fibrous forms of'these minerals-that~ is, amosite-do not show, the characteristic oblique extinction of'the parent minerals. This i's due to lamel- lar twinning on a molecular level' as shown inithis dia• gram. Repeated lamellar twinning produces a com- posite crystal which shows nearly parallel extiinctionn with refractive indices close toa and y in one view, but y' and (i whenirotated'90'° about its length. As a resultt of lamellar twinning„amosite fibers show very low ex- tinction angles(©-5°) and, therefore; may be confusedl with anthophyllite. 52. Here are the dispersion staining data for a typ- ical amosite. This example happens to be a grunerite with refractive indices just'above the divisiom line be- tween cummingtonite and gru nerite. 53. When observed with the annular stop in the Car- gillle 1.680' liquid, this amosit'e showsa blue color with xa about 480, nm, parallel to the length, and an oran9e or reddishbrown col'orcrosswi'se corresponding to a. xo, of'about700' nm. r 54. Corresponding central stopicolors are golden- yellow parallel to the length, and blue-green cross- ~ ~ wise: You will see these colors in the 1.680 liiquid quiite ~. often with asbestos products.. 55: The birefringence for amosite is moderate (about 0:025); as shown in this photomicrograph taken with crossed'polars.. 56. Addition of' a first-order red compensator shows the sign of elongation to be positive. 57. The last of the asbestos minerals is riebeckite, which Ini its fibrous form is caliledi crocid'olite: Rie- beckite, like other amphiboles, except for anthophylL lite, is monoclinic, although the obiique extinction angle is very small (1-3"). As usual in the asbestos minerals, crocidolite also exhibits a, range of sollid' solutions and its refractive indices may vary consider-, ably depending on the extent of replacement of mag-, nesium by iron. Most commercial crocidolite ori'g-, inatedi from South Africa with a small amount from, 1iVfestern, Australia; and tihe indices are high corre- sponding to a hilghi ironi content~ and you should ex•, peet to see a, (i, andi y values close to 1'.70 or above. The birefringence is relatively low, and the fibers are further distinguished by a blue transmission color. Secause the crystals are anisotropic, the blue trans- mission colors vary with direction; that is, the fibers are pieochroie. In the lengthwise direction cor- responding approximately to the a refractive-index di- rection4 the color is a deep blue, whereas in the cross- wise vibration directions, (f and y, the colors are lighter gray-blue. These pleochroic colors, the highirefractive ), ° ;•,••;•:t;frRitillW'Tme' yVr0r

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