what is talc

7/28/2019 What is Talc

1/17

Robert A. C l i f ton 1

W h a t Is T a l c ?

RE F E RE NCE : C l i f t o n , R . A . , "W h a t I s T a l c ? " Def ini t ions for Asbestos and OtherHea l th-Related Si licates , AS TM STP 834, Benjamin Levadie, Ed., American Society forTesting and Materials, Philadelphia, 1984, pp. 158-174.ABSTRACT: Talc is a hydrated magnesium silicate produced by the metamorphosis ofdolomite and quartzose rocks or by the hydrothermal alteration of ultramafic and maficrocks. As the changes are rarely complete and uniform, the rocks usually contain one ormore other minerals. In pure form it is the softest of minerals. Talc is an extremely usefuland economically important mineral and is, like most materials, hazardous to a degree.This paper takes the position that talc is a victim. It is a victim of the imprecision ofmineral terminology, which does not distinguish between the fibrous and nonfibrous va-rieties o f several amphiboles. It is a victim of the terminology o f its ow n industry, whichsold "fib rous tal c" for many years. It is victimized because precursor minerals in fibroushabit produce pseudomorphic talc fibers. Those same fibers are sometimes unaltered andpresent in talc in just enough quantity to give a near truth to claims that talc containsasbestos. Talc is a vic tim of monitoring m ethods that are totally nonspecific and call eachelongate particle of whatever origin a fiber and, by analogy, asbestos. Most especially,talc is a victim of imp recise asbestos definitions, w hich allow the inclusion o f mostamphibole particles of some elongation in those definitions.KEY WORDS" health-related silicates, talc, asbestos, definitions

W h e n a s b e s t o s b e c a m e a c a u s e o f s e r io u s e n v i r o n m e n t a l c o n c e r n i n t h e e a r l y1 9 7 0 s , a s e g m e n t o f t h e t a lc i n d u s t r y p e r c e i v e d t h a t th e l a c k o f r ig o r i n a s b e s to sd e f i n i t io n s p o s e d a n i m m e d i a t e t h re a t to it s o w n o p e r a t i o n s a n d a l o o m i n g t h r e a tt o o t h e r s e g m e n t s o f t h e A m e r i c a n m i n e r a l s i nd u s tr y . T h e U . S . B u r e a u o f M i n e s( U S B M ) a g r e e d w i t h t h at a s s e s s m e n t a n d h a s e x p e n d e d c o n s i d e r a b l e e f f o r t i nt r y i n g t o a s si s t th e r e g u l a t o r y a g e n c i e s i n th e u s e o f a c c u r a t e m i n e r a l o g i c a l t e r m s .2I n 1 9 7 6 t h e U S B M e s t a b l is h e d t h e P a r t i c u l a te M i n e r a l o g y U n i t t o h e l p c l a r if yt h e c o n f u s i o n i n p a r t ic u l a t e m i n e r a l o g y t e r m i n o l o g y , t o d e v e l o p a s o li d sc i e n t i f i cb a s is f o r r e s e a r c h i n t o p a r t i c l e -r e l a t e d p o l l u t i o n p r o b l e m s , a n d t o p r o v i d e t e c h -n i c a l a d v i c e a n d a s s i s t a n c e t o r e g u l a t o r y b o d i e s . T h e s u c c e s s o f th e s e e f f o r ts c a nb e j u d g e d i n th e l i g h t o f t h e n e e d f o r s u c h a p u b l i c a t i o n a s th i s .

Q u i t e a g o o d e x a m p l e o f t h e a b u se s t h a t g r o w o u t o f t h e m i s u s e o f m i n e r a lt e r m s c a n b e f o u n d i n t h e t a l c i n d u s t r y .

l Physical scientist, Division o f Industrial M inerals, U .S. Bureau of Mines, W ashington, D.C .20241.This paper does not address the question o f the health ha zards of fiberform talcs since it isagainst U.S. Bureau of Mines policy to evaluate health data.

Copyright* 1984 by A STM lntcrnational15 8

www.astm.orgCopyright by ASTM Int'l (all rights reserved); Sat Jun 23 13:42:11 EDT 2012

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2/17

C LIFTON ON W H AT TALC IS 159D e f i n i t i o n s

T h e f o l l o w i n g d e f i n i ti o n s a r e u s e d f o r t h e te r m t a l c :1 . T h e p u r e m i n e r a l :

(a ) Mg6(SisO20(OH)4) [1] . 3( b) 6 3 . 3 6 % S iO 2 , 3 1 . 8 9 % M g O , a n d 4 . 7 5 % H 2 0 .( c ) A sof t p l a t y m i n e r a l .

2 . A r o c k c o n t a i n in g a m i x t u r e o f h y d r o u s m a g n e s i u m m i n e ra l s, w i t h ac o m p o s i t i o n r a n g i n g f r o m p u r e t a lc t o p r e d o m i n a n t l y t re m o l i te [ 2 ].

3 . T a l c u m , s o a p s t o n e , s t ea t it e , p o t s t o n e , a n d F r e n c h c h a l k .

W h a t T a l c I sT a l c is p r o d u c e d b y th e m e t a m o r p h o s i s o f d o l o m i t e a n d q u a r t z o s e r o c k s o r

b y t h e h y d r o t h e r m a l a l te r a ti o n o f u l t ra m a f i c a n d m a f i c ro c k s . A s t h e c h a n g e sa r e ra r e l y c o m p l e t e a n d u n i f o r m , t h e r o c k s u s u a ll y c o n t a i n o n e o r m o r e o f t h em i n e r a l s l i s t e d i n T a b l e 1 [ 3 ] .

N o t e t h a t b o t h t r e m o l i t e a n d a n t h o p h y l l i t e c a n o c c u r i n f i b r o u s f o r m s a n d a l s ot h a t c h r y s o t i l e is th e f i b r o u s f o r m o f se r p e n ti n e . T h e s e a s s o c i a t e d m i n e r a l s a r ea s o u r c e o f m u c h t r o u b l e t o t h e ta l c in d u s t r y . T a b l e 2 s h o w s t h e v a r ia t i o n s i nc o m p o s i t i o n o f t h e m i n e r a l s a s s o c i a t e d w i t h t a lc .

T h e o t h e r n a m e s f o r t a lc n e e d l i tt le e x p l a n a t i o n . T a l c u m , o f c o u r s e , i s i d e n t i fi e da s th e m a i n i n g r e d i en t o f m o s t c o s m e t i c p o w d e r s . S o a p s t o n e g e t s i ts n a m e f r o mi ts g r e a s y f e e l , a n d t h e t e r m i s u s u a l l y r e s e r v e d f o r th a t l e s s p u r e t a l c t h a t i su s e d f o r c a r v i n g . S t e a t i te i s a m o r e d e n s e , p u r e r t a lc , w h i c h c a n b e m a c h i n e d ,a n d t h e t e r m i n c l u d e s i t s s u c c e s s o r , t h e b o n d e d , m o l d e d t a l c u s e d i n e l e c t r o n i c s .T h e t e r m p o t s t o n e r e f e r s to a u s e o f ta l c d u r i n g p a s t m i l le n i a , e v e n p r e d a t i n g

TABLE 1--M iner als tha t commonly occu r in talc deposi ts .M ineral Grou p Phase Formula

Carbonates calcite CaCO3dolomite CaMg(CO3)2magnesite MgCO3Amphiboles tremolite~ Ca2Mg~SisOzz(OH)2anthophyllite~ (FeMg)TSisO22(OH)2Serpentines antigorite Mg3Si2Os(OH)4c hry so tile ( u n c o m m o n ) Mg3Si2Os(OH)4lizardite (uncom m on) Mg3Si2Os(OH)4Other quartz SiOzmica, e .g ., p h l o g o p i te Kz(Mg,Fe)6[Si6AI2020](OH)4chlorite, e.g., p e n n i n i t e (Mg,Al,Fe)~2[(Si6AlsO20](OH)~6pyrophyllite AL[(SisO20](OH)4"Occurring in fibrous and nonfibrous forms. Other trace phases are o ften present but are notincluded.3 The italic num bers in brac kets refer to the list of references appen ded to this paper.

Copyright by ASTM Int'l (all rights reserved); Sat Jun 23 13:42:11 EDT 2012




3/17

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4/17

CLIFTON ON WHAT TALC IS 161r e c o r d e d h i s t o r y , w h e n t h i s m i n e r a l w a s c a r v e d to m a k e c o o k i n g p o ts . S o m et a l c is s ti ll s a w e d i n t o h a n d y p i e c e s , a n d t h i s " F r e n c h c h a l k " i s u s e d f o r m a r k i n gm a t e r i a l s t o b e w e l d e d .

T a l c h a s b e e n f o u n d v e r y u s e f u l i n m a n y i n d u s t r i e s . T h e u s e o f t h i s u n i q u em a t e r i a l is e n h a n c e d b y i t s l o w c o s t [ a n o m i n a l $ 2 8 p e r m e t r i c to n ( $ 2 5 p e r s h o r tt o n ) f o r c r u d e o r e i n 1 9 8 2 ] .

T h e U n i t e d S t a te s i s th e w o r l d ' s f o r e m o s t p r o d u c e r a n d e x p o r t e r o f t a lc [ 4 ].T h i s m i n e r a l , p r o d u c e d f r o m 3 5 m i n e s i n 11 s t a te s in 1 9 8 1, w a s w o r t h n e a r l y$ 1 0 0 mi l l i o n , an d t h e 1 .1 - mi l l i o n - me t r i c - t o n ( 1 .2 - mi l l i o n - to n ) an n u a l p r o d u c t io ni s e x p e c t e d t o d o u b l e b y t h e y e a r 2 0 0 0 [ 5] . T a b l e 3 s h o w s t h a t re s o u r c e s i n t h eU n i t ed S t a t e s a r e s u f f i c i en t t o p e r mi t t h i s ex p an s io n , i n t h e ab s en ce o f s e r io u se n v i r o n m e n t a l c o n s t r a i n ts .

F i g u r e 1 i s a d i a g r a m m a t i c v i e w o f w o r l d t al c s u p p l y a n d d e m a n d a s o f 1 9 7 8 .W o r ld p r o d u c t io n i s o n t h e l e f t , s o u r ce s o f s u p p ly i n t h e U n i t ed S t a t e s a r e i nt h e m i d d l e , a n d t h e m a j o r e n d u s e s a r e o n t h e r i g h t .

T h e e n d u s e s s e r v e d b y g r o u n d t a l c ( a n d h e n c e i t s m a r k e t d i s t r i b u t i o n ) a r ed e t e r m i n e d b y i t s d i v e r s e p r o p e r t i e s , i n c l u d i n g i t s c h e m i c a l a n d m i n e r a l o g i c a lc o m p o s i t i o n , p a r t i c l e s i ze a n d s h a p e , s p e c i f ic g r a v i t y , h a rd n e s s , a n d c o l o r .

T h e l a rg e s t us e o f t a lc i s i n th e m a n u f a c t u re o f c e r a m i c s - - s a g g e r b o d i e s a n do th e r k i ln f u r n i tu r e , s an i t a r y w a r e , f l o o r an d w a l l t il e , d in n e r w ar e , g l aze s , an de l ec t r i c a l p o r ce l a in s . I n t h is ap p l i ca t i o n , t h e ad d i t i o n o f t a l c t o t h e u s u a l c l ay -s i l ic a - f e l d s p a r b o d y m i x t u r e s f a c il i ta t e s t h e f i ri n g o f t h e w a r e a n d i m p r o v e s t h eq u a l i ty . T h e c e r a m i c i n d u s tr y u s e d 3 8 % o f th e g r o u n d t a l c i n th e U n i t e d S t a te si n 1 9 81 . M u c h o f t h e ta l c u s e d b y t h e c e r a m i c i n d u s tr y i s a m i x t u r e o f p l a t yt a l c a n d b l o c k y t r e m o l i t e .

Th e s ec o n d m a jo r u s e o f t a l c (2 1 % in 1 9 8 1) i s a s fi l l e r an d p ig m en t f o r p a in t s .W h e n u s e d i n p a i n t s, t h e p l a t y v a r i e ti e s o f t a l c h a v e g o o d h i d i n g p o w e r , a c t a sp i g m e n t s i n t h e ir o w n r i g h t, a n d s e r v e t o e n ta n g l e a n d b u o y u p p a r t i c le s o f o t h e r

TABLE 3- -W or ld talc and related minerals resources, a in million s hort ton units, bGeographical Area Reserves Other TotalNorth Am e~caUnited States 150 600 750Other 10 40 50

Total 160 640 800South Am erica 5 20 25Europe 60 190 250Africa 5 20 25A sia and Oceania 100 400 500

W orld tota l 330 1300" 1600"In collaboration with the U.S . Geo logical Survey.bl sho rt ton = 0.9 m etric tons.CThe data do not add to the total sho wn because of independent rounding.





5/17

1 6 2 D E F I N I T IO N S F O R A S B E S T O S A N D H E A L T H - R E L A T E D S IL I C A T E SW O R L D P R O D U C T IO N

It iBRAZIL265 ] [ UNITED1,325STATES

I F IN L A N D I F R AN C E2 1 5 3 3 5l N O R W A Y [ IT A L Y121E 1 9 3

U .S S R ] R E P U B LIC5 2 0 E O FK O R E A7 3 3L - o l -C H I N A K O R E A1 6 5 [ 1 4 0 EIN D IA ] AUS TRA L IA3 4 O 1 6 5[ ,J A P A N O T H E R1 , 4 ~ 3 6 8

I I!W O R L D T O T A L6 , 4 7 5 E

2

I ,1 0

1

I IM P O R T S ~ . ~" 1 9

J iN D U S T R TT O C K S1 / 1 / 7 82 1 0 J

K E YE : ESTIM ATEOS I C : T A N O A R GN D U S T R I A LLASSIFICATION

FIG. 1--Talc supply-demand relationships in the United States fo r 1978,

p i gm en t s , t hus he l p i ng t o keep t hem i n suspens i on du r i ng p ro l onged s t o rage .The proper t i es of t a lc impor tan t to the pain t indus t ry are i t s co lor , f ineness , o i labso rp ti on , ch em i ca l i ne r tnes s , and o p t i m um v i scos it y .The p l as t i c s i ndus t ry , w i t h i t s needs fo r bo t h r e i n fo rcem en t m a t e r i a l s and

economic f i l l e rs , has recognized tha t t a lc sa t i s f i es bo th requi rements , and theindus t ry was the th i rd l arges t user of t a lc minera l s in 1981, wi th 11% of thegrou nd ta lc market . Talc can be used as a f i l l e r o r re inforcem ent or bo th , in bo tht he rm ose t t i ng and t he rm op l as t i c r e si n s . I t i m proves chem i ca l and h ea t r e s i s tance ,d im ens iona l s tab i l i ty , s ti f fness , hardness , therm al condu ct iv i ty , t ens i l e s t rength ,creep res i s tance , and e lec t r i ca l insu la t ion . Talc a l so improves processabi l i ty .Copyright by ASTM Int'l (all rights reserved); Sat Jun 23 13:42:11 EDT 2012




6/17

C L IF T O N O N W H A T T A LC IS 16 3

N O U , , R ,S T O C K ,]

L ] E XP O R T S2 5 7G O V E R N M E N TTOCKPILER A L A N C E. . . . . . . . . . . . . . . . . . . 2B L O C KN D U M P. . . . . . . . . 1G R O U N D. . . . . . . . . . . . . . . . . . 1

C R U D E1 0 6I ~RO~.~YLLnE113

U . S .O E M A N D

IPROCESSED j1 , 0 3 0

I

T A L C I1 7!G R O U N O913

.

i n 1 0 0 0 s h o r t to n u n i ts ( 1 0 0 0 s h o r t t o n s = 9 0 7 m e t r i c t o n s ) .

CE RA M I CS [2 5 7S I C 2 5 3 , 2 6

S IC2 8 4 4~ 13

S IC 8 7 9P A I N T1 9 2 ]S I C 8 5 1P A P E R I87S IC 6 2 1

PLASTICS1 4 7S IC 2 8 2 1REFRACTORIES6

S IC3 2 9 7I R O O F IN G I1 9S IC 2 9 2

I R U B B E R ]3 6S I C 0 6 9

" I O T H E R8 8

F o u r t h i n o rd e r am o n g t h e o u t l e t s fo r d o m es t i c t a l c m i n e ra l s i s i t s u s e fo rco a t i n g an d l o ad i n g o f h i g h -q u a l i t y p ap e r s. In t h i s ap p l i ca t io n , h i g h -p u r i t y ta l ch e l p s i n o b t a i n i n g a p ro d u c t w i t h t h e d e s i r ed we i g h t an d o p ac i t y , g o o d i n kr e t e n ti o n , a n d s u p e r i o r s u rf a c e t e x tu r e . A t o ta l o f 9 % o f t a lc c o n s u m p t i o n w e n ti n t o th e p ap e r i n d u s t ry i n 1 9 8 1 . T a l c ' s ab i l it y t o we t o i l m a t e r i a l s p re fe ren t i a l l yi n th e p r e s e n c e o f w a t e r m a k e s i t a v e r y e f f e c t i v e p i tc h c o n t r o l a g e n t i n p a p e rm a n u f a c t u r i n g .

A n o t h e r m a j o r u s e o f m i n e ra l s o f t h e t a lc g ro u p i s in ag r i cu lt u ra l ch em i ca l su s ed a s ca rd e r s o r d i l u en t s fo r i n s ec t i c i d e s . Ta l c m i n e ra l s a r e e s p ec i a l l y u s e fu lf o r t hi s p u r p o s e b e c a u s e t h e i r c h e m i c a l i n e rt n e ss m a k e s t h e m c o m p a t i b l e w i t h





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1 6 4 D E F I N I T I O N SFOR ASB EST OS AND HEALTH-RELATED SILICATES

a v a r i e t y o f t o x i c s u b s t an ces , wh i l e t h e i r p h y s i ca l ch a rac t e r i s t i c s f ac i l i t a t e t h ed i s p e r s i o n an d i n c rea s e t h e e f f ec t i v en es s o f th e s e ag en t s .

F o r ro o f i n g m a t e r i a ls , i n c l u d i n g ta r p ap e r , a s p h a l t s h in g l e s , an d ro l l r o o f i n g ,t h e ad d i t i o n o f t a l c p ro v i d es a s u r f ace t h a t is n o n s t i ck i n g , ch em i ca l l y i n e r t, f i r er e t a rd an t , an d we a t h e r r e s is t an t.

In co s m e t i c an d p h a rm a ceu t i ca l u s e s , t a l c s m u s t b e s e l ec t ed t o m e e t th e h i g h es ts t an d a rd s o f p u r i t y , s o f t n e s s , p l ea s an t f ee l , co l o r , ch em i ca l s t ab il i ty , an d f r ee d o mfro m an y g r i t , i r r i tan t s , o r b ac t e r i a l co n t am i n a t i o n .

Th e u s e o f t a l c m i n e ra l s i n r e f r ac t o r i e s h a s m u ch t h e s am e r a t i o n a l e a s t h e i ru s e i n ce ram i cs .

W h en u s ed i n ru b b e r , t a l c m i n e ra l s a c t a s f i l le r s , p ro v i d i n g i n te rn a l l u b r i ca ti o n .Th ey a l s o s e rv e a s n o n s t i ck d u s t i n g ag en t s .Th e r em a i n i n g t a l c u s e s i n t h e Un i t ed S t a t e s i n c l u d e s u ch d i v e r s e m i n o rap p l i ca t io n s a s i n ag en t s fo r ch em i ca l wa r fa re , f l o o r wa x es , s h o e p o l i s h es , p ean u tp o l i s h i n g , an d s a l am i d u s t i n g .S o m e w h a t m o r e t h a n o n e h a l f o f t h e to t a l d o m e s t i c o u t p u t o f ta l c is d e r i v e df r o m o p e n - p i t o p e r a ti o n s , w i t h t h e b a l a n c e c o m i n g f r o m u n d e r g r o u n d m i n e s . I nb o t h t y p es o f o p e ra t i o n s , t h e ex t r ao rd i n a ry s l i p p e r i n e s s o f t a l c o re i m p o s es u n -u s u a l t r a c t i o n p ro b l em s i n m i n e l o ad i n g an d h au l i n g ; i n u n d e rg ro u n d m i n es i ta l s o c r ea t e s s l ip p ag e p ro b l em s i n c r ib b i n g an d t i m b e r i n g . M i n i n g o p e ra t i o n s a r eu s u a l l y ca r r i ed o u t b y co n v en t i o n a l d r i l l i n g an d b l a s t i n g m e t h o d s . Th e s o f t n e s so f t a l c m ak es m i n i n g an d p ro ces s i n g ea s i e r t h an i t i s fo r m o s t m i n e ra l s .

S e l e c t i v e m i n i n g a n d h a n d s o rt in g a r e t h e m e t h o d s m o s t c o m m o n l y r e s o rt e dt o fo r i m p ro v i n g t h e q u a l i t y o f t h e o u t p u t o f c ru d e t a l c -g ro u p m i n e ra l s , b u t f ro t hf l o t a t io n is b e i n g em p l o y ed i n c rea s i n g l y t o r eco v e r t a l c (F i g . 2 ) [6 ] .W h a t T a l c I s N o t

Ta l c i s c e r t a i n l y n o t a s b es t o s , a l t h o u g h i t c an b e p s eu d o m o rp h i ca l l y f i b ro u s .N o t t o o m a n y y e a r s h a v e p a s s e d s i n c e t a l c p r o d u c e r s w e r e s e l l i n g " f i b r o u s "t a l c s u n d e r s u ch n am es a s F i b ren e an d A s b es t in e . In m o s t o f t h e s e s o -ca l l edf i b ro u s t a l c s , t h e f i b ro u s co m p o n en t was h a rd l y ev e r p s eu d o m o rp h i c t a l c , b u twas m o s t o f t en c l eav ag e f r ag m en t s o f m as s i v e ac t i n o l i t e o r t r em o l i t e .S o u r c e s o f R e a l o r A p p a r e n t F i b e r s

W h en t a l c c ry s t a l l i z e s o u t o f a s o l u t i o n o f i t s co m p o n en t s , a s i n t h e h y d ro ~t h e rm a l a l t e r a t i o n p rev i o u s l y m en t i o n ed , i t i s fo l i a t ed o r m as s i v e , t h e f i r s t t wof o r m s m e n t i o n e d b y D a n a a n d F o r d [ 7 ] . P s e u d o m o r p h i c t a l c , t h e t h i r d f o r ml is t ed b y D a n a a n d F o r d , i s th e o n l y f o r m f o r w h i c h t h o se a u t h o r s m e n t i o n e v e nap p a ren t f i b ro s i t y . W h en m e t am o rp h o s i s o ccu r s , t h e f i n a l m i n e ra l u s u a l l y a s -s u m e s t h e f o r m o f i ts p r e d e c e s s o r. I f a f i b r o u s m i n e ra l w e r e t o b e m e t a m o r p h o s e di n t o t a l c , an ap p a ren t t a l c f i b e r wo u l d b e c r ea t ed .

S ev e ra l i n d u s t r i a l u s e r s o f t a l c h av e b een c i t ed b y t h e Occu p a t i o n a l S a fe t yan d H ea l t h Ad m i n i s t ra t i o n (OS HA ) fo r in f r ac t i o n s o f t h e a s b es to s r eg u l a t i o n s .





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CLIFTON ON WHAT TALC IS 165

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J F R O IH L O T A T IO N N i c ke I.C o b ~ 1o n c e n t r a t ea n d M a g n e s i teIC o n c e n ~ e t e T a i l i n g sI T , , ~ II . L T E ~ ]

. 1FIG. 2-- F lowsheet of production by the Eastern M agnesia Talc Co. in Vermont.

O S H A b a s e d i ts f i n d i n g s o n t w o o b s e r v a b l e f ac ts : f ir st , p ar ti cl es w e r e f o u n d i nt h e a ir t h a t m e t t h e f e d e r a l f i b er c r it e ri a o f e q u a l i n g o r e x c e e d i n g a n a s p e c t r a t ioo f 3 : 1 a n d b e i n g a t l e a s t 5 t ~ m in l en g t h , a n d s e c o n d , t h e re w a s s o m e t r e m o l i t ea l s o p r e s e n t i n t h e a ir . T h e r e w a s n o e f f o r t b y t h e i n s p e c t o r s t o d e m o n s t r a t e t h a tt h e e l o n g a t e p a r t i c le s w e r e t r e m o l i t e o r t h a t, i f t r e m o l i t e , t h e y e v o l v e d f r o mt r e m o l i t e a s b e s t o s a n d n o t f r o m t h e u s e fu l m a s s i v e t r em o l it e .

T h e U S B M h a s lo n g r e c o g n i z e d t h e u t il it y o f th e a ir b o rn e f ib e r m o n i t o r i n ga n d c o n t r o l m e t h o d d e v e l o p e d b y t h e B r i t is h f o r u s e i n t h e ir a s b e s t o s t e x t i lef a c t o r i e s. I t i s a v a l i d a s s u m p t i o n t h a t in that envi ronment e v e r y e l o n g a t e p a r t i c l ei n t h e a i r b e a r s a r e l a t i o n s h i p t o t h e a s b e s t o s i n t h e a i r a n d t h a t a d i m i n u t i o n o ft h e ir n u m b e r w o u l d r e d u c e t h e h a z a r d . I t i s n o t v a l i d i n t h a t, o r a n y o t h e r ,e n v i r o n m e n t t o a s s u m e t h a t m i n e r a ls c a n b e i d e n ti fi e d b y m e a n s o f a n o p t ic a l





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166 DEFINITIONSFOR ASBESTOS AND HEALTH-RELATED SILICATESm i c ro s co p e o r t o ca l l ev e ry p a r t i c l e w i t h a 3 : 1 a s p ec t r a t io e i t h e r a s b es t o s o r af i b e r an d a s c r i b e t o i t t h e d em o n s t r a t ed h aza rd s o f a s b es t o s .

T h e U S B M f in d s i t s e lf t o d a y i n f u ll a g r e e m e n t w i t h t h e c o n c l u s io n s o f t h eNa t i o n a l B u reau o f S t an d a rd s (NB S ) i n t h e i r 1 9 7 7 r ep o r t [8 ] . Th a t r ep o r t s t a t e st h a t , a f t e r e f fo r t s t o an a l y ze t h e f i b e r co n t en t o f 8 0 ta l c s am p l e s u s i n g t h e O S H Ap r o c e d u r e s , i n t h e i r o p i n i o n th e e x i s ti n g O S H A p r o c e d u r e w a s u s e f u l o n l y f o rd e t e rm i n i n g f i b e r co n t en t an d n o t a s b es t o s co n t en t ; t h a t t h e p ro b l em o f t h ed e f i n i t i o n o f a s b es t o s r em a i n s ; an d t h a t an accep t ab l e r e s o l u t i o n o f t h a t p ro b l emm u s t p r e c e d e d e v e l o p m e n t o f a c c e p ta b l e m e a s u r e m e n t t e c h n iq u e s a n d s ta n d a rd s .Th e d a t a i n Tab l e 4 , t ak en f ro m a s t u d y b y Am p i an [9 ] , i l l u s t r a t e t h a t t h o s em i n e ra l s t h a t fo rm i n f i b ro u s h ab i t an d a re a s b es t o s can h av e o t h e r fo rm s an d ,i n s o m e c a s e s , o t h e r n a m e s .N o t e t h a t s e v e r a l o f t h e m i n e r a l s h a v i n g t h e s a m e c h e m i c a l f o r m u l a a n d(a l t h o u g h n o t s h o w n ) i d en t i ca l c ry s t a l s t ru c tu re s h av e b o t h f i b ro u s an d n o n f i b ro u san a l o g s . F u r t h e r , t h e h ab i ts a s c r i b ed t o ac t i n o l it e an d t r em o l i t e co u l d ea s i l y b efo u n d i n n o n as b es t o s e l o n g a t e p a r t i c l e s .

T a b l e 5 , t a k e n f r o m C a m p b e l l e t a l [10], i l lu s t ra t e s t h e s em an t i c s i de o f t h ep ro b l em . M i n e ra l o g i s ts an d t h e i n d u s t ry , fo r t u n a t e l y , h av e g i v en d i f f e r en t n am est o t h e f i b ro u s fo rm s o f s e rp en t i n e , r i eb eck i t e , an d cu m m i n g t o n i t e -g ru n e r i t e , b u t ,u n fo r t u n a t e l y , t h ey n eg l ec t ed t o d o s o fo r an t h o p h y l l i te , t r em o l i t e , an d ac t i n o l i te .Th i s g i v e s r i s e t o s u ch q u es t i o n s a s " I s t r em o l i t e a s b es t o s ?"

T A B L E 4- -S om e f ibro us and non f ibrous serpentines and amphibole minerals a nd varie t ies wi tht he i r formu l as .Mi n era l Fo rmu l a Fo rm i n W h i ch I t Ap p ea rs

Serpent inesChrysotileAnt igori teLizardite JAmp h i b o l e sAnthophyl l i t e

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3 M g O 9 2SIO2 9 2 H2 0

4[(MgFe)TSisO2:(OH)2]

2[CadMgFe)sSisO22(OH)2]4[(FEZ+Mg)TSisO22(OH)2]

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fibrous and nonfibrou sserpentines

f ibrous and nonfibrousorthoamphibolesclinoamphiboles, oftenacicular and lath-shaped,rarely fibrousf ibrous c l inoamphibolederived from grunerite-cum mingtoni te ser ieswi t h i ro n ab o u t 5 .5 , m ag n es i u mabout 1.5n o n f i b ro u s amp h i b o l en o n f i b ro u s amp h i b o l ec l inoamphibole , f ib rousvarie ty of r iebecki ten o n f i b ro u s amp h i b o l e





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C L I F T O N O N W H A T T A L C IS 1 6 7

T A B L E 5--Asbestos and analog forms.Asbestos Nonasbestos Analog

Chrysotile antigorite-lizarditeCrocidolite riebeckiteAmosite cummingtonite-gruneriteAnthoph yllite asbestos anthophylliteTremo lite asbestos tremoliteActinolite asbestos Actinolite

F i g u r e 3 , t a k e n f r o m u n p u b l is h e d U S B M r e s e a rc h s h o w s t h e X - r a y d i f f ra c t io np a t t e rn o f a s am p l e o f t r em o l i t i c t a l c . Th e p eak s i d en t i fy t h ree o f t h e m i n e ra l sp r e s e n t. T h e i n s tr u m e n t , h o w e v e r , c a n n o t d if f e r e n ti a te b e tw e e n f i b ro u s a n d n o n -f i b ro u s m i n e ra l s .

Th e au t h o r h a s i n h i s f i l e s a l ab o ra t o ry r ep o r t , f ro m a s u p p o s ed l y r ep u t ab l ec o m m e r c i a l l a b o r a t o r y , s a y i n g t h a t a s a m p l e f r o m a t a l c m i n e c o n t a i n e d 4 0 %a s b e s t o s . U p o n q u e r y , t h e l a b o r a t o r y a d m i t t e d t h a t t h e y h a d n o t e v e n m a d e ap e t r o s c o p i c o r m i c r o s c o p i c e x a m i n a t i o n a n d o n l y q u a n t i f ie d t h e t r e m o l i t e p e a k s ,ca l l i n g t h em a s b es t o s .

F i g u r e 4 f r o m C a m p b e l l e t a l [10] i s a p h o t o g rap h o f a n ea r l y p u re t r em o l i t ero ck . Th i s is t h e fo rm t h a t b y f a r th e l a rg e s t p o r t io n o f t h a t m i n e ra l t ak es u p o nf o r m a t i o n . T h i s f o r m i s o b v i o u s l y n o t, n o r e v e r c o u l d b e , a s b es to s . I f , h o w e v e r ,a n y o n e w e r e t o c r u s h o r m i ll t h is r o c k , c l e a v a g e f r a g m e n t s c o u l d b e p r o d u c e d ,a n d s u c h fr a g m e n t s m i g h t b e " f e d e r a l f i b e r s , " w h i c h w o u l d m e e t t h e r e g u l a t o r yag en c i e s ' d e f i n i t i o n s o f a s b es t o s w i t h o u t ev en co m i n g c l o s e t o b e i n g t h e t ru et r em o l i t e a s b es t o s p i c t u red i n F i g . 5 , a l s o f ro m C am p b e l l e t a l [10].

F i g u r e 6 , e x c e r p t e d f r o m a r e c e n t N a t i o n a l T o x i c o l o g y P r o g r a m d r a f t m a n -u s c r i p t , i l lu s t ra t e s p e r f ec t l y h o w n o n f i b ro u s m a t e r i a l c an b eco m e a s b es to s u n d e rt h e p re s en t d e f i n i t i o n s . Th e f i rs t two s en t en ces , f ro m t h e ab s t r ac t , t e ll o f t h eh ea l t h e f f ec t s .

T h e a m p h i b o l e g r o u p o f m i n e r a ls m e n t i o n e d in T a b l e 1 i s t h e s o u r c e o f f i v eo f th e a s b es t o s m i n e ra l s an d i s u b i q u i t o u s , o ccu r r i n g i n m u ch o f th e ea r t h ' s c ru s tan d i n m o s t m i n i n g a rea s i n t h e Un i t ed S t a t e s an d e l s ewh e re . Th e p ro c l i v i t y o ft h i s g ro u p o f m i n e ra l s t o c l eav e ( s p l i t ) a l o n g d e f i n i t e , p a ra l l e l , c l o s e l y s p acedp l a n e s m a k e s c e r t a i n t h a t t h e s e m i n e r a l s w i l l p r o d u c e " f e d e r a l f i b e r s " w h e nc r u s h e d o r g r o u n d .Th e am p h i b o l e s a r e p re s en t i n p rac t i c a l l y a ll ig n eo u s -m e t am o rp h i c ro ck t e r r a i n ,an d i t is n o co i n c i d en c e , a s s h o w n i n F i g . 7 , t h a t th i s t e r ra i n co n t a in s a l l o f o u rt a l c m i n es .

F i g u r e 8 , f r o m C a m p b e l l e t a l [10], i s abou t t remo l i t e bu t i s il lu s t ra t ive o f a l la m p h i b o l e s . N o t e t h a t m o r e t h a n 7 0 % o f t h e g r o u n d t r e m o l i te r o c k p a rt ic l e s h a v e





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14/17

C L IF T O N O N W H A T T A L C IS 1 7 1

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Survival was co , arable tn the tr mo l t te and control groups. Noto xt ct ty or increase in neoplasta was observed in the t romo ltto exposed animalscompared to the concurrent controls.

Under the conditions of th ts bfoassoy, conftbrous t ron~li to was not tox icand did not cause s carcinogenic response Mien ingested at a level of 1~ in thedfe t by male and female Fischer 344 rats for th ei r lt fe tfma,

Crysta111ma tremollte was chosen fo r th ts study because up to 20 years agoI t ~S a common contaminant of to lc Milch was used tn foods and phamacouttcals.The grtndlng of tr tq ol tt n In preparatlon for I ts tntonded uso may result in theproduction of ftbers Mitch havo the Qorph010~ of L~bestos idnera ls. Stanton(1981) in ravtewtog hts tnt rapleural wlneral deposition sl~dtes speoulated th at~Az~aothe as~stos xtnoraljques tton my be ~lrect ly related to ~lber slze So contrastto chemical ~o s t t l on . Therefore, the s~d~ of cry sUl ltn o ~emoltte ~sdeemed spproprtate becouse~ t~r i ts past vddespreod exposure a~d the fac t that t tassumes fiber characteristics Mien ground in the processing of talc.

FIG. 6 --E xc erp t fro m a National Toxicology Program draft document.

a l e s s t h a n 3 : 1 a s p e c t r a t io , w h i l e m o r e t h a n 4 0 % o f t h e p a r ti c l es f r o m t r e m o l i tea s b e s t o s h a v e a n a s p e c t r a t io h i g h e r th a n 1 0 : 1 .

A n e w A S T M s ta n d ar d , th e A S T M P r a ct ic e fo r S af e ty a n d H e a l th R e q u ir e -m e n t s R e l a t i n g t o O c c u p a t i o n a l E x p o s u r e t o A s b e s t o s ( E 8 4 9 - 8 2 ) , g i v e s p a r t i a lr e c o g n i t i o n t o t h e i n a d e q u a c i e s o f p r e v i o u s d e f i n i t i o n s b y d e f i n i n g f i b e r s a sm o n i t o r e d p a r t i c l e s w i t h a n aspect ratio of at least 5:1, a m i n i m u m l e n g t h o f5 I xm , a m a x i m u m d i a m e t e r o f 3 t xm , a n d t h e a p p e ar a n c e o f f a s c i n e s , o r b u n d l e so f s t ic k s . N o t e t h a t i n F i g . 8 m o r e t h a n 7 0 % o f t h e m i l le d t r e m o l i te a s b e s t o sw o u l d m e e t t h a t c r it e r io n , w h i l e m o r e t h an 9 0 % o f t h e m i l le d t r e m o l i te r o c kw o u l d n o t.





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172 D E F I N I T I O N SFOR ASB EST OS AND HEALTH-RELATED SILICATES

FIG. 7--Distribution of igneous metamorphic rock terrain (top) and talc deposits (bottom) in theUnited States.Summary

T a l c i s a n e x t r e m e l y u s e f u l a n d e c o n o m i c a l l y i m p o r t a n t m i n e r a l . I t i s , l i k em o s t m a t e r i a l s , h a z a r d o u s t o s o m e d e g r e e .

1 . I t i s a v i c t i m o f th e i m p r e c i s i o n o f m i n e r a l t e r m i n o l o g y , w h i c h o f t e n h a sn o t d i s ti n g u i s h e d b e t w e e n t h e f ib r o u s a n d n o n f i b r o u s v a r i e t ie s o f s e v e r a l a m -p h i b o l e s .

2 . I t i s a l s o a v i c t i m o f th e t e r m i n o l o g y o f it s o w n i n d u s t r y , w h i c h s o l d" f i b r o u s t a l c " f o r m a n y y e a rs .





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CLIFTON ON WHAT TALC IS 1 7 3

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l O / \/ \/ ~ , , , ~1:1 3:1 5:1 10:1 20:1 50 :1 1 0 0 : 1 200:1

ASPECT RATIOFIG. 8--Particle size distribution of milled tremolite and tremolite asbestos.

3 . P recu r s o r m i n e ra l s i n t a l c i n f i b ro u s h ab i t c an y i e l d p s eu d o m o rp h i c t a l cf i b e r s . Th o s e s am e f i b e r s a r e s o m e t i m es u n a l t e r ed an d p re s en t i n t a l c in j u s ten o u g h q u an t i t y t o g i v e a n ea r t ru t h t o c l a i m s t h a t t a lc co n t a i n s a s b es t o s .

4 . Ta l c i s a v i c t i m o f m o n i t o r i n g m e t h o d s t h a t h av e o f t en b ee n n o n s p ec i f i ca n d h a v e c a l le d e a c h e l o n g a te p a r t i c le o f w h a t e v e r o r ig i n a f i b e r a n d , b y a n a l o g y ,a s b es t o s .

5 . M o s t e s p ec i a l l y , t a l c is a v i c t im o f i m p rec i s e a s b es t o s d e f i n it i o n s , wh i cha l l o w t h e i n c l u s i o n o f m o s t am p h i b o l e p a r t i c l e s o f s o m e e l o n g a t i o n i n t h o s ed e f i n i t i o n s .R e g u l a t o r y a g e n c i e s s h o u ld b e c o m e m o r e a w a r e o f th e s h o r t c o m i n g s o f c e rt a i n

o f t h e i r f i b e r m e a s u r e m e n t m e t h o d s , i n c lu d i n g t h e i d e n ti f ic a t io n o f p a r t i c le c o m -p o s i t i o n an d c ry s t a l l i n e h ab i t b y u s i n g m e t h o d s s u ch a s e l ec t ro n d i f f r ac t i o n an dm i c r o s c o p y .Referen ces

[1 ] D eer, W. A. , How ie, R. A ., and Zussman, J., Rock-Forming Minerals, Wiley, New York,1963.[2] Brobst, D. A. and Pratt, W. P., United States Mineral Resources, Geological Survey Profes-sional Paper 820, U .S. G overnment Printing Office, Washington, D .C ., 1973 , pp. 619 -626 .Copyright by ASTM Int'l (all rights reserved); Sat Jun 23 13:42:11 EDT 2012




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174 DEFINITIONSFOR ASBESTOS AND HEALTH-RELATED SILICATES[3] Ro hl , A. N. , Lange r , A. M. , Se likoff, I . J . , Tord in i , A . , Kl ingent id i s , R. , B owe s, D. R. ,and Skinner , D. L. , "Consumer Talcums and Powders : Minera l and Chemical Charac ter iza-t i o n , " Journal o f Tox ico logy and Env i ronment a l Heal th , Vol . 2 , 1976 , pp . 255-284 .[4] Ro e , L . A. , "T a l c an d Py ro p h y l l i t e ," Indus t r ia l Mi nera l s and Rocks , 4th ed . , S . J . Lefond ,Ed. , Am erican Ins t i tu te of Mining , M eta llu rg ica l, and Petro leum Engineers , New York , 1975 ,pp. 1127-1147.[5] C l i f to n , R . A. , "T a l c , " M inerals Yearbook, Vol . 1 , U.S. Bureau of M ines , U.S. G overn m entPrin t ing Off ice , Wa shington , D .C. , 1982, pp . 827- 832 .[6 ] C l i f t o n , R . A. , "Ta l c : Mi n e ra l Fac t s an d Pro b l ems , " Bureau o f Mi nes Bul l e ti n , Vol. 671,1980, p. 903.[7] Dana , E. S. and Ford , W. E. , A Textbook o f Mineralogy, 4th ed . , W i ley , New Y ork , 1960 ,p p . 6 6 7 -6 7 8 .[8] " A Report o f the Fiber Conten t o f Eighty Indust ria l Talc Samples O bta ined From and Usingthe Procedures of the Occupational Safety and Health Adm inistrat ion (O SH A )." N ationalBu reau o f S t an d a rd s , Wash i n g t on , D.C . , May 1 9 77 .[9] Am pian , S. G. , "A sbe stos Minera l s and The i r Nonashestos A nalo gs ," paper presen ted a t theSym posium on Elec t ron Microscopy of Microfibers , Pennsylvan ia State U nivers i ty , Un ivers i tyPark , Pa . , 2 3-2 5 A ug. 1976 (avai lab le f rom S. Amp ian , U.S. Bureau of M ines , W ashington ,D.C . ) .[10] Campbel l , W. J . , Blake , R. L. , Brown, L. L. , Cather , E . E. , and Sjoberg , J . J . , "Selec tedSil icate M inera ls and The ir As best ifo rm Varieties: Mineralogical Definit ions and Identificat ion-Ch arac ter iza t ion ," BuM ines IC 8751, U.S. Bureau of Mines , Washington , D .C. , 1977 .



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