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National Bureau of Standards Special Publication 506. Proceedings of the Workshop on Asbestos: Definitions and Measurement Methods held at NBS, Gaithersburg, MD, July 18-20, 1977. (Issued November 1978) HISTORY OF ASBESTOS-RELATED MINERALOGICAL TERMINOLOGY Tibor Zoltai Department of Geology and Geophysics University of Minnesota Minneapolis, Minnesota 55455 Abstract Asbestos-related mineralogical terms such as fiber, fibrous, orm asbestos-like, and asbestos have been misinterpreted and ing the last few years in the literature of environmental MNAand public health studies. The new definitions are inadequate for the proper description and study of various mineral particles and, at the same time, are causing considerable confusion in interdisciplinary communication. The meaning of these terms is traced through the history of mineralogy. It is demonstrated that: the use of the•term fiber has always required some resemblance to organic fibers; fibrous has been the term describing a crystallization habit in which the mineral appears to be composed of fibers; asbestiform has been used, without exception, to describe a special fibrous habnt in which the fibers have higher tensile strength and flexibility than crystals in other habits of the same mineral; asbestos was initially the name of an independent mineral species and gradually became a collective term applied to all asbestiform varieties of minerals. Ney words: Acicular; amphibole; asbestiform; asbestos; fiber; fibrous; fragments; mineralogical; serpentine; terminology. Introduction Until a few years ago there was no problem with the asbestos-related mineralogical terminology. Mineralogists knew exactly what other mineralogists meant when they used terms like asbestos, asbestiform, fibrous, and acicular, even if some of these terms, like asbestiform, are not always defined in textbooks. The last syllable of asbestiform (that is, -form) is consistent with several adjectives used for the description of textures or crysta~Tazation habits (e.g., reniform, filiform, dentiform, coiloform). Consequently, it is understood, without question, that asbestiform is a descriptive term for a certain texture or crystallization habit. This situation of content was suddenly changed less than five years ago, when through the focusing of public and scientific attention on asbestos pollution this portion of the mineralogical terminology was picked up by environmental and public health scientists, by engineers and by lawyers. Unfortunately, they did not adopt the terminology as used by mineralogists but have introduced a redefinition of most of the critical expressions, in spite of the objection of leading mineralogists. The most important of these arbitrary changes of definitions included: (1) Asbestos is understood by mineralogists as a collective term referring to the unusual crys~Tization of certain minerals in the form of long, strong, and flexible fibers, aggregated in parallel or radiating bundles from which the fibers can easily be 2063104803

separated. The definition accepted by the Minnesota District Court during the trial of Reserve Mining Co. [63, p. 24],t however, was a different one: Asbestos is a generic term for a number of hydrated silicates that, when crushed or processed, separate into flexible fibers made up of fibrils. (emphasis by the author) By this definition ali amphiboles and a number of other minerals became possible candidates for inclusion in the term asbestos. Because of the perfect prismatic cleavage, upon crushing, amphiboles always produce acicular fragments. Of course, acicular fragments are not fibers, are not flexible and are not composed of fibrils. However, they may not be distinguishable from asbestos fibers in routine electron microscopic examination. In order to get around that problem the term fiber had to be defined in a more practical sense. (2) The redefinition of fiber (U.S. District Court, District of Minnesota, Fifth Division, Fall, 1973) that was soon adopted by most environmental and public health scientists [28, p. 5] states that a fiber is: a mineral which is at least three times as long as it is wide.2,a This definition of fiber eliminated the difficult task of testing the flexibility and the presence of fibril composition of submicroscopic particles, and retained only the shape of the particle as a decisive criterion. Accordingly, all acicular amphibole cleavage fragments became fibers and as indirectly implied, all amphibole minerals became asbestos. (3) Leading mineralogists objected to calling amphibole cleavage fragments, asbestos fibers and amphiboles, asbestos minerals. In order to overcome that objection two less frequently used terms, "asbestiform" and "asbestos-like", were redefined in line with the new definitions of asbestos and fiber. The new definitions were introduced in the Minnesota courtroom [63], and subsequently in the language of the news media and the environmental literature: Asbestiform became a prefix added to the name of any mineral which is known to occur on occasion andlor produce "fibers" when crushed. Asbestos-like was defined as any hydrous silicate particle which is at least threeT nger than wide, that is, which is a°fiber". Thus, all amphiboles became asbestiform minerals,° instead of asbestos minerals, and amphibole fragments became asbestos-like fibers, underscoring its implied relationship with asbestos. These new definitions provided a simplified mineralogical interpretation for the complex and not fully resolved problem of asbestos mineralogy. It simplified the identification of mineral particles by eliminating the need for distinction between asbestos fibers and acicular cleavage fragments. A fiber can simply be identified by its shape (>3:1 aspect 1Figures in brackets indicate the literature references at the end of this paper. 2The 3>1 aspect ratio limitation In the description of fibers was used before by some British and American regulatory agencies. However, this was the first incident when this fiber description became an asbestos fiber identification, as the use of the term fiber im~plfed an identity between appropriately shaped amphibole fragments and amphibole asbestos fibers. This implicative use of the 3>1 aspect ratio is apparent in most current environmental studies. 311; should be noted that sedimentologists use the term acicular for the description of particles "whose length is more than three times its width"T2-f7.p_5]. 4The expression "asbestiform amphiboles" is basically valid. However, in the context of the new definitions it is erroneous as it includes all amphiboles. According to the proper mineralogical terminology the same expression 7s limited to those amphibole crystals'which actually grew in the asbestiform habit. 2

ratio) and if its composition and lattice matches that of an amphibote, that particle can be called ®asbestiform" amphibole, or simply, "asbestos". Consequently, all available data on the health hazards caused by the inhalation of asbestos fibers can be applied to acicular amphibole fragments, thus eliminating the need for the extensive job of determining the nature and the extent of the health effects of the actual particles, that is, the acicular amphibole fragments. On the other hand, the new definitions created serious problems, probably not forseen by the promoters of the new definitions. For example, jade became an asbestos in spite of the fact that jade is the toughest known natural substance [8]. One type of jade (nephrite) is mineralogically actinolite-tremolite, and according to the new definitions, it is an "asbestiform mineral" and its acicular fragments are "asbestos-like fibers". The other type of jade is jadeite, a pyroxene. Pyroxenes are similar to amphiboles as far as both are chain silicates and break into acicular fragments. The only major difference between these two groups of minerals, in terms of their qualifications for "asbestos", is that pyroxene is not "hydrated". Consequently, in terms of the new definitions jadeite is not an asbestos. However, one could argue whether the presence of OH is really necessary in the definition of asbestos.s At the same time the new definitions include many non-asbestiform mineral varieties in the rank of asbestos, they also exclude a number of other minerals, (e.g., non-hydrous silicates) which in fact may also crystallize occasionally in asbestiform habit. Most of these minerals are rare and are not known to constitute commercial deposits. Nevertheless, a mineralogical definition should not be tied to commercial criteria. The new definitions, of course, magnify the extent of the potential asbestos pollution problem by an exponential factor. If all amphiboles are "asbestiform" and their fragments are °'asbestos-like" then every state in the union has some asbestos in the soils, drifts, and bedrocks. Kryvial, Wood, and Barrett show [44, p. 13] the distribution of "high con- centration of asbestiform phases" of rocks in the continental United States. Only a few of the amphibole-bearing rocks included in that survey contain even a minor fraction of known, true asbestiform varieties of amphiboles. the new definitions are not only contrary to mineralogical traditions but are inadequate for crystal chemical descriptions. They also can lead to ambiguity and contradiction. For example, Kryvial, et al. in their monograph [44, p. 5] wish to exclude hornblende from the 11asbestiform" category of amphiboles; apparently because hornblende seldom crystallizes in asbestiform habit. However, the new definition of "asbestiform" does not allow them to use it in that sense, or to express the same concept in any other non-ambiguous way. They try to get around the problem by using the term fibrous in an ambiguous way by stating that hornblende is '°seldom seen in a fibrous form". Yet in page 3 of the paper they state that all amphiboles "fragment into fibers", whether they are products of an "acicular form of a fibrous crystal" (7) or not. They admit that at a microscopic scale the fragments of hornblende are no different from that of other amphiboles. Apparently, what they are trying to say is that fibrous is not always fibrous, but the new terminology does not allow them to distinguish between these two types. The proper mineralogical terminology can do that. Most mineralogists object to the misuse of the mineralogical terminology. Some mineralogists, however, have found themselves in situations where compromise was necessary and they used the new definition of fiber (>3:1 aspect ratio) and the term "fibrous" in an accordingly loose context [42,45,71], sometimes with comments on the disciplinary restric- tions of that terminology [11].e slt is not entirely impossible that the minute acicular crystals of jade may turn out to possess some asbestos properties. In that case minute fragments of jade could appropri- ately be called asbestiform fibers. sThe authors of [11] accept the new definition of fiber "in the context of studies of health hazards". 3 2063104805

The true background and character of mineralogical concepts and the seemingly complex definition of the asbestos-related mineralogical terminology can be best illuminated through a historical analysis of the relevant terms and expressions. That will be attempted in the following pages. Historical Review Asbestos 9n history. Asbestos is probably the most unique substance in the mineral kingdom. To begin with, it does not even look like a stone, but looks more like some organic wool or cotton. Good quality asbestos is more elastic than other minerals and its high tensile strength is unique. Asbestos is not only stronger than organic fibers but it is also more durable, is fireproof, and for all practical purposes, amphibole asbestos is chemically inert. The peculiar properties of asbestos have attracted the attention of man throughout history. In early times the use of asbestos was restricted either to the households of powerful and rich royalties or to special geographic areas. There are records that Egyptians, Greeks, Romans and even earlier civilizations had knowledge of asbestos and used it for special purposes. The Eqyptians sometimes used coarse asbestos cloth to protect the embalmed bodies of Pharaohs from the ravages of time. The Romans made cremation wrappings to collect the unspoiled ashes of emperors. The lamps of the Vestal Virgins were furnished asbestos wicks which lasted forever. There are also some questionable records that the Romans threw asbestos and other toxic substances in the river flowing through the besieged city of Auxium, in order to break the resistance of the defendants. According to legend, Charlemagne had an asbestos tablecloth which he threw in the fireplace after dinner for the purpose of cleansing it, to the amusement of his company (fig. 1). Figure 1. Ge Boot's (6] illustration of the fire-proof property and the making of asbestos cloth. As it can be expected, in addition to the practical uses there were some less logical and more mysterious applications of asbestos in early and in superstitious civilizations. In medieval times, for example, asbestos was used as a major ingredient in an ointment (fig. 2) intended to cure a number of diseases. Loosely translated De Boot's prescription reads: "Multiple application, miraculous asbestos ointment for juvenile tinea (head-fungus?) and shinbone (skin?) ulcer. Take 4 oz. asbestos, 12 oz. lead (oxide?), 2 oz. zinc oxide, and calcinate, thereupon pulverize into glass while adding vinegar, and agitate it daily for a month; after a month boil it for a quarter hour and let it cure until it becomes clear; thereafter add some vinegar, mix it with rose-petal oil until it becomes a homogeneous ointment: then go and smear it over the infant's head, to promote healing: for itches and shinbone ulcer smear it over the 4

affected area in the evening, for healing. The same mineral, mixed with aqua vitae and bamboo syrup, when applied in small quantities in the morning will sooth the pain of female white-menstruation (leukorrhea?), and will soon heal." Aa,a.. £t Amianta linimeutamadtrineampuerorum, 6!•s.r• & ad uleera tibiaru miraculoCum fit Cequenn mo- '"i^"" do. Accipiuntur Amiand une.quatuora plumbi uncix ta,mtizuncizdue,aculcinancur, deinde srmrsei. pulverifauinvitromaurantureumaeeco,acquo- tidicpermenCemmateriaagicamrfemoapo(tmen; fcm ebulliendaoR unius harm quadrante, ac quie- fcere fudtut, donec indarefcar. deinde illius ueti clariquandras, cumpari.quantirateolei roGcei. miCacmr,donec bona 6atunio Hnimentiforma: co innngiturceput pncrf tomtn ut eiro fanemc ad fea- bicm, & ulcera tibiarum refperi pucee unguntur, .rd.ln- donee Ganentur. Si laapis hie cum aqua vit.T, & Cae-t& :haro Colvatur,ac exigea portio mane quoridiemu-e f~tla licri albo monRruo laboranti decur,moc fanacur. mt,~a# Figure 2. De Boot's prescription for the miraculous asbestos ointment [6, p. 384-5]. The industrial revolution opened an era yielding rich rewards for imaginative inven- tions. Asbestos, as other unique minerals, did not escape attention and a large number of applications were discovered. Some of these were practical and were adopted, such as fire- proof suits and other products (fig. 3). Some, on the other hand, were not well received by the public, like the refillable asbestos cigarette paper introduced in England during the 1880's [38]. If Figure 3. Illustration of some early asbestos products, Jones [38]. 5

Actually, industry was rather slow in adopting asbestos. Even after the discovery of the extensive and high-quality Canadian chrysotile deposits, asbestos-industrialists spent more time promoting their product than manufacturing it,7 at least for a few decades. After the turn of the century they began to succeed and asbestos soon became one of the most widely used industrial minerals.- Asbestos in mineratoriv Although there were several references to asbestos in the ancient literature, the first scientific-type descriptions were offered relatively late by Dioscorides [20] and Plinius [55]. Dioscorides called it auiavrco amiantos (meaning immaculate, unpolluted) and Plinius added a comment that the Greeks used to call it aosaatoo, asbestos (meaning incombustible, unquenchable, inextinguishable). Plinius also used the Latin name of linum vivum for the same mineral as he believed it to be a plant from India; a plant which grew in a part of the earth burned completely by the sun, thus became accustomed to that environment and learned to survive in the flame of fire. During the scientifically dormant Middle Ages the nomenclature of Dioscorides and Plinius was neither challenged nor modified. Of the two names of asbestos, amiant appeared to be the more popular. Almost two centuries ahead of the era of the scientific revival, Agricola [1] offered in 1546 the first criteria for mineral identification. According to Werner [66], Agricola recognized several basic categories of mineral properties such as color, transparency (translucida), resplendence (fulgor), luster (mitor), weight (gravitas), hardness (durities), flexibility (flexibilitas), cleavage (fissio), etc., and used descriptive terms as: globular (figura globi), cyclindrical (figura cyclindrica), conical (figura metae), hair-like (figura capillorum), star-like (figura stellarum), etc. It is easy to recognize in Agricola's expressions the prototypes of some modern terms. Although he did not expand our knowledge of asbestos, he did introduce the descriptive term capillary (haarf6rmig, hair- like) which was adopted later for the description of the shape of asbestos fibers. The next stage of development in mineralogy was during the 18th century when scientists began the development of a mineralogical system divided into orders, classes and species on the basis of common and distinct external properties. These followed the natural history concepts and criteria used in botany and zoology. The first and still relatively crude classification was offered by Walerius [65] and by Cronstedt [15] and the first significant improvement of Agricola's list of external characters of minerals, and its application in mineral classification, was offered by Linneaus [47]. The term fibrous (fibrosum) appeared in his list of descriptive terms for minerals composed of parallel fibers. This period was closed by Werner who published the first comprehensive and consistent system of mineralogtr in 1774 [66]. He exerted unparalleled influence on the future development of mineralogy.8 His influence extended from the wide-spread acceptance of his svstem of mineralogy to the establishment of mining schoois in many countries and to the practice of naming new minerals after personal names. In his classification system, capillary is to be used for the description of asbestos fibers and fibrous is used to describe the breakage of bundles of fibers into small fibers.e He constructed a complete system of minerals of about 300 species. Although never published, it was spread by his students and fellow m neralogists [34,26], and was.adopted all over the 7Jones' book [38] may have been inspired by similar interests. He writes [38, p. VI] that "he hopes by this means (writing the book) to ... tend to develop the uses of" asbestos. °Werner used the name orvctoanosy for determinative mineralogy, after the Greek opvtoo (fossil) and yvaota (to know). sNote that there is very little difference between saying that (1) fibrous crystals grow in bundles of fibers (as we would say it today) and (2) a bundle of fibers breaks down to fibrous crystals. However, the use of fibrous as a description of breakage was soon changed to a description of texture or habit by &lum (5, p. 30], Thomson [61, p. 2567, Phillips [54, p. XXXVI and LXXII], etc. 6

civilized world, even before his death in 1817. In his system he recognized one asbestos species, with four subspecies, and two other [26] subspecies, asbestartioer or asbestarticher, one of actinolite and one of tremolite.so Werner recognized a number of other fibrous, but not "asbestartiger" mineral varieties. He called those strahliger or fasriger. Jameson [36,37] translated Werner's terminology into English as asbestous, rism tic, and fibrous,x' respectively for asbestartiger, strahliger, and fasriger. The comparison of the appropriate portion of Werner's and Jameson's classification are given in Table 1. Table 1. Comparison of Warner's and Jameson's classification of asbestos and some fibrous minerals. Werner, after Fretesleben [26] Jameson [36] ERSTE KLASSE: ERDLICHE FOSSILIEN 3. Kiesel Geschlecht Spischaft des Pistazits 52. Anthophyllite a. strahlicher Sipschaft des Zeoliths 75. Prehnit a. fasricher 77. Zeolith b. Faser - Zeolith 5. Talk Gaschlecht Sipchaft des Talks CLASS II. ORDER VI. SPAR Genus I. Schiiier Spar S. Prismatic Schiller Spar or Anthophyllite Genus IV. Prehnite 1. Axotomous Prehnite 2d Subsp, Fibrous Genus IV. Zeolite 7. Prismatic Zeolite lst Subsp. Fibrous Genus VIII. Augite 137, Asbest 2. Hemiprismatic Augite a. b. Bergkork Amianth 4th Subsp. Actynolite lst Kind Asbestous c. d. gemeiner Asbest Bergholz 2d 3d -- Common -- Glassy Sipschaft des Strahlsteins 5th Subsp. Tremotite 138. Strahlstein 1st Kind Asbestous a. asbestarticher 2d -- Common b. gemeiner 3d -- Glassy c. d. giasicher kbrnicher 6th Subsp. Asbestus lst Kind Rock-Cord 141. Tremolit 2d -- Flexible Asbestus a. asbestarticher 3d -- Common Asbestus b. gemeiner 4th -- Rock-Wood c. glesicher 'oThe actual names of classification units vary from author to author. In order to avoid the lengthy comparison of the expressions used by different authors only "species", "subspecies", or "varieties" are used in the text (instead of "subspecies" and "kinds" of Jameson, for example). "Phillips and Allen [54, p. LXXII] used asbestiform as well as a special term fasciculated for minerals composed of fibers or acicular crystals occurring in bundles. 7 2063104809

i Jameson's asbestous was soon changed to asbestiform in English mineralogy textbooks: Thomson in 1836 61, L, p. 22;, Phillips and Allan in 1838 [54, p. 58] and QanaSZ in 1857 [17, p. 153]. Ha"uy [36] also adopt2d Werner's basic system and terminology, and translated most of his German terms into French, although he practiced more flexibility than Jameson did as he introduced a more chemical classification scheme. However, he makes no apparent distinction between asbestos and other fibrous varieties and uses the term fibreux for all. He trans- lated Werner's asbestartiger Strahlstein and Tremolit as Actinot~breux and Grammatite fibreuse,13 fasriger Prehnite as Prehnite fibreuse, and straliger Antophyllit as anthophyl- lite aciculaire. Although he does not distinguish between asbestos and other fibrous crystals, he seem to restrict the use of fascicle, and to a lesser degree fibre, to asbestos fibers. The term filamenteux was introduced into the French mineralogical 7iterature by Brard [7], asbestoid by Beudant [4, p. 369] and asbestiforme by Cloizeaux [13, I, p. 80] as equivelent expressions for the German asbestartig and the English asbestiform. It should be noted that all these early mineralogists, including Werner and his followers, used the term fibrous in a general sense and considered asbestiform (asbestous, asbestartig, feinfaserig, asbestoid) as a special class of fibrosity. Although none of them have defined the uniqueness of asbestiform fibrosity, the reason for that distinction was implied in their recognition of the unique properties and appearance of asbestos, including the unusual strength of asbestos fibers. Hoffmann (and Breithaupt) [33, IIb, p. 307], for example, pointed out that the asbestiform variety of tremolite is less brittle, that is, stronger than the common prismatic or acicular variety. i r t Figure 4. Handcolored illustrations of Schilletnder Asbest (Amianth) and gemeiner (comewn) Tremolit in Schmidt's Mineralienbuch [60]. i2At the bottom of this page Dana gives some exercise questions like: What is the crystal- lization of hornblende? Mention the characters of the varieties of actinolite - (i.e., glassy, radiated, asbestiform, massive). L3occasionally, however, he used the German word "asbestartiger" in the French text without translation. a

Werner's historical system of mineralogy was used without fundamental modifications for over a century, especially in popularized mineralogy books like that of Schmidt's [60]. Werner's strong influence on mineralogy resisted, for some times, the acceptance of the proposals of a new breed of mineralogists who advocated to change the system of mineralogy from the "natural history" type to a more chemical one. Mineralogists like Thomson [61], Beudant [4], Berzelius [57], Rammelsberg [56], and others believed that the chemical properties of minerals are much more important than their external and physical properties. Thomson was a strong opponent of the classification of minerals on the principles of natural history. He was especially critical of Mohs [49] who carried the natural history approach to such an extreme that it almost became free of chemistry. Thomson came out to say [61, p. 8]: "It appears to me, that mineralogy is so closely connected with chemistry, and so dependent on it for its specific distinctions that it would be highly injurous to it, and therefore, very unwise to attempt to deprive it of so important an ally." In line with the emphasis on chemistry came a new classification and the redefinition of mineral species. All those former species which had no distinct chemical composition were discredited. This included the degradation of Werner's one asbestos species to the rank of variety. Of course, asbestiform actinolite and tremolite were already considered variations (or subspecies) by Werner himself. Asbestos and its subspecies became classified, on the basis of relatively poor and inconsistent chemical analysis, as variations of amphiboles, epidote, pyroxenes, talc, and tourmaline by Beudant [4, p. 837], for example. Rammelsberg expressed this philosophy of the reclassification of the former asbestos species" [56, Part II, p. 313] as: "Mineral substances described by the name of asbestos (or amiant) do not appear to constitute an independent species. As their chemical composi- tions indicate, and it may be more appropriate as noted by Breithaupt, that the name asbestos represents a condition which can be obtained by several, thoroughly different kinds of minerals." (emphasis by author) Berzelius, the Swedish chemist-mineralogist (also the major promoter of the "blowpipe analysis" which became one of the major mineralogical techniques for more than acentury), was one of the most ardent pioneer advocates of this "scientific" system of mineralogy. In his 1846 publication [54, p. 213-214] Berzelius states that mineral s ec~ies as previously defined don't exist. He proposed that instead of species, m nerals should be identified and classified on the basis of: "ingredients and different chemical proportions...as well as their definite bonding relationships." (Yerbindungsverhtiltnisse = 2= crystal structure.) The transfer of mineralogy from Natural History to Chemistry did not take place as proposed by Berzelius and his compeers. Instead, mineralogy developed gradually in that direction and assumed a unique position among the sciences, a status of transition between natural history and physical sciences. The concept of species was not fully abandoned either. In fact, with the meaning redefined in a chemical context, "mineral species" is still used today by some mineralogists, like Berry and Mason [3, p. 272-274]. The classification of minerals was also changed during the second half of the 19th century from categories of "common external properties" to groups of chemical units. Mineral species or individual minerals were defined by their chemical composition and crystal structure. Of course, crystal structures were not known at that time. Consequently, they had to be substituted for by the observable consequences of the crystal structure: the crystallography and physical- chemical properties of minerals. That is, if two minerals had the same composition but had different crystallography and physical properties they were considered to be two distinct minerals. That criterion was readily applicable to minerals which occurred in good crystal forms. However, the same could not be used for asbestos where there was not crystallographic Y4In the same book Rammelsberg recognized Krokydolite (crocidolite), named by Hausmann in 1831, as an independent species. That may, at first, look like a contradiction in his philosophy. However, it is not, as crocidolite's parent mineral riebeckite was only discovered many years later, in 1888, by Sauer. 9 2063104811

data and the only non-chemical information available was the difference in the tensile strength and flexibility of the asbestiform versus the compositionally equivalent non- asbestiform mineral. That difference was considered by many mineralogists to be sufficiently distinct to warrant the recognition of some asbestiform varieties as independent minerals. Several dozen asbestos mitaerals were proposed and accepted during this stage of evolution.15 The chemical compositions of most of these asbestos minerals were known and their chemical identity with other minerals were recognized. The compositional equivalence of chrysotile and serpentine was realized since Kenngott's publication [40] in 1853. That was sufficient for some mineralogists to declare chrysotile as a variety of serpentine. Others, however, still considered the differences in physical properties sufficiently significant to recognize chrysotile (under various names, like: metaxite, schweizerite, etc.) and serpentine as two distinct minerals. The other two major asbestos minerals, byssolite and crocidolite, were known to match amphibole compositions, byssolite since Scheerer's 1851 analysis [59] and crocidolite since Delasse's 1847 analysis [i9]. Crocidolite was first believed to be an asbestiform variety of arfvedsonite [50, p. 461] in spite of minor chemical differences. However, as soon as riebeckite was discovered by Sauer in 1888, crocidolite was reclassified by Naumann (and Zirkel) [51, p. 707], as its asbestiform (Asbestform in German) variety. As a consequence of the undecisive significance of differences in physical properties versus compositional identities, the classification of asbestos minerals as independent minerals or as varieties was a function of the individual interpretation of mineralogists. For example, Hintze [317, Groth [297, and Naumann (and Zirkel) [51] recognized chrysotile as a variety of serpentine and crocidolite as a variety of riebeckite; E. S. Dana [16] classified both as independent species; Klockmann [41] and Rogers [58] recognized chrysotile as an independent mineral and crocidolite as a variety of riebeckite. The asbestos nomenclature was further complicated during the last decades of the 19th and first decades of the 20th century when asbestos became a major industrial material. The industrially useful properties of asbestos obtained from certain deposits differed somewhat from that of others, and on the basis of that some asbestos were given distinct mineral names, usually reflecting the name of a mining company or district (for example, bostonite: Boston Asbestos Packing Co.; amosite: Asbestos Mines of South Africa; montasite: Montana mine, South Africa; prieskaite: Westerburg mine, Prieska, South Africa . he use of these distinct mineral names, of course, provided some promotional advantages. The majority of these commercial mineral names never got into mineralogy text books, and those few which did were subsequently eliminated or discredited. Amosite, for example, was formally discredited in 1946 [2]. The discovery of x-ray diffraction produced a tool available for crystal structure determination. As the basic crystal structures of the former asbestos minerals were proven to be identical with that of compositionally equivalent major minerals they were all degraded to the rank of varieties, without further arguments. For example, the final decision on crocidolite's mineralogical identity with riebeckite was provided by Whittaker in 1949 [67] and by Drysdall and Newton in 1960 [22]. The asbestos varieties of minerals were consequently identified by the prefix of fibrous or asbestos-like [24, p. 578] or asbestiform (see Table 2 for details). Fibrous16 was used as a more general term to include both asbestiform and non- asbestiform fibrous minerals. However, asbestiform was always restricted to asbestos varieties, as that was done consistently since Werner s time, 200 years ago. tsThese asbestos mineral names included: Adigenite, agalite, antholite, baltimorite, beaconite, cyclopeite, dermatite, fibrolite, griquanlandite, hydrophite, ishkyldite, karachaite, kolskite, kymantine, metaxite, nemalite, picrolite, retinalite, rezhikite, rhoduzite, schweizerite, vorhausite, williamsite, zermattite, zillerite, xylotite, etc. 1eFord [24, p. 204] gave a more liberal definition of fibrous than usual. He states that "fibres may or may not be separable" in a fibrous mineral. 10

e Z3 Table 2. Descriptive term~ used by mineralogists to distinguish between asbestos and other types of fibrous textures. (Frequently in conjunction with fibrous.) Page number of an example is given. Werner (Friesleben) asbestartich Naumann [50, p. 324] asbestartig [66, p. 107 Naumann (Zirkel) Asbestform HaDy [30] no distinction [51, p. 707] Hoffmann (Breithaupt) asbestartig Nicol [52, p. 152] asbestiform [33, 2b, p. 306] Tschermak [62, p. 444] ? feinfaserig Jameson [36, II, p. 22] asbestous Groth [29, p. 151] asbestartig Phillips (Allan) asbestiform [54, p. 58] E. S. Dana [16, p. 384 asbestiform Thomson [61, I, p. 481] asbestiform Hintze [31, II, p. 1195] ? feinfaserig Mohs (Haidinger) asbestous Klockmann [41, p. 567] ? feinfaserig [49, II, 27] Doelter [21, II, p. 589] asbestartia Beudant [4, p. 387] asbestoide Rogers [58] no distinction Brard [7, p. 206] filamenteux Ford [24, p. 578] asbestos-like Bium [5, p. 242] ? feinfaserig Hurlbut [35, p. 446] asbestiform Rammelsberg [56, p. 358] asbestartig Kraus, Hunt, Ramsdell asbestiform Schmidt [60, p. 358] asbestartig [43, P. 392] Bristow [9, p. 85] asbestiform Berry, Mason asbestiform [3, P. 527] Cloizeaux [13, p. 81] asbestiforme Deer, Howie, Zussman asbestiform J. D. Dana [17, p. 153] asbestiform [18, II, P. 2431 a French: fibreux; German: faserig. The term fiber, in reference to asbestiform fibers, was equivalent to the concept of organic fibers because the early natural historians believed that asbestos was actually a vegetable. Mineralogists from the 18th century on did not specifically state that the term fiber is used because of its resemblance with organic fiber. However, that reasoning is apparent in their description of asbestos fibers as hair-like or capillary or thread-like, and in the types of names they have given to asbestos minerals, such as mineral-wood, rock- cotton, mountain cork, rock-wood. Jones [38] provided extensive details in the description of the similarity between asbestos and organic fibers (fig. 5) and concluded [38, p. 221] that: "The nature of the asbestos fibre is thus so far identical in structures with the organic fibres." - 11 N 0 a w 0 A 00 M+ W

C;w Fg. 1. Bibrv of 9hoo '* p WaaL Magti@°d Fig. 2. Filnmenh B00 of Naw Cattan. di.mchn. No. 1.-TLOtfmd On. Fig. 5. 8pun Ghw. Nn. 7. 13etfo~d O». Figure 5. Jones' [38] comparison of asbestos and organic fibers. Although the use of the term fiber has not been restricted to asbestos and included a number of other minerals they all had some characteristics reminiscent of organic fibers. In any case, the term fiber has never been used as a description of the elongated shape of crystals. For that acicular is the proper mineralogical expression. The term asbestos was first a species name, as noted earlier it was introduced by Werner and his school. Later it became a collective term, like c1Tys or gems, in reference to asbestiform varieties of a number of otherwise unrelated minerals. Parallel with the mineralogical terminology asbestos also became an industrial term for a category of mineral products containing asbestiform varieties of silicates. However, some commercial asbestos may be mixed with non-asbestiform acicular crystals or cleavage fragments. The quality of asbestos is related to: (a) the extent of the development of the preferred asbestos character (high tensile strength, flexibility, length of fibers) of the asbestiform fibers, and (b) the percentage of the less desirable non-asbestiform, acicular crystals or cleavage fragments present in the product. That is, the mineralogical and industrial definitions of asbestos are not fully coincident. The unusual properties of the asbestiform fibers were always recognized by the early users of asbestos as well as by mineralogists. These properties included high tensile strength [for example, 32,33,38,64], increased flexibility (noticed by all mineralogists), unexpected optical properties [for example, 53,69] and differences in surface properties, like surface charges [for example, 28,42,45,72]. VO Fig. 3. Fig. 4. Fibro of p,adint'Chro.d of HsvSilk Gmden Spid.. . 12

.4 With the introduction of high-power electron microscopy, a new tool for mineralogical research and a new area of applied mineralogy was established. Electron microscopes permitted the examination of extremely small mineral particles and the study of the fiber of fibril structures of various asbestiform crystals. The long suspected cylindrical (tubular, scroll-like) structure of the chrysotile fibrils [68] was directly observed by Maser et al. in 1960 [48] and a more detailed record was offered by Yada [70]. In addition to th`e cylindrical fibril structure, Cressey and Zussman [14] reported on a polygonal chrysotile structure which appears to be the dominating fibril structure in the so called "schweizerite" and "Provlen-type" chrysotile varieties. Comparable work, although with less spectacular results, was done on asbestiform amphiboles by several investigators, for example, Chisholm [12], Franco, Hutchinson, Jefferson, and Thomas [25]. The asbestiform amphibole fibril structure appears to be more subtle than that of chrysotile. The increased tensile strength and flexibility may be due to the presence of systematic defects such as faults, dislocations and twinning, and/or to the lack of surface defects. Of course, we know that defects can interfere with the cleavage and fracture of solids and are frequently introduced artifically in alloys and other crystals to enhance their strength as it is elaborated on in the textbook of Kelly and Nicholson [39]. Undoubtedly, time and extensive research will be needed before the structural causes of the unusual properties of asbesti- form amphiboles will be fully explained. Conclusions Several conclusions can be drawn from this review of the history of asbestos-related mineralogical terminology and its current misuse in environmental sciences: (1) Terms such as fiber, fibrous, asbestiform, and asbestos, have distinct meanings in mineralogy whether or not we can offer a complete crystal structural explanation for the development of the properties, reflected by these terms. (2) The asbestos-related mineralogical terminology is adequate and clear, and is not in need of revision. However, its full understanding requires a relatively comprehensive knowledge of mineralogy. Consequently, a set of detailed and unambiguous definitions should be prepared for inter- disciplinary use. (3) The asbestos-related mineralogical terms have been grossly misinterpreted in most of the recent literature of environmental sciences. The implied definitions are inadequate for the description and discussion of the crystal chemical and crystal physical properties of minerals, and endanger the success of coordinated, interdisciplinary studies aimed at the understanding and the solution of the health hazards created by asbestos pollution. The presence of any forei n particle in air and waters in excessive quantities is undesirable and is potentially harmful. It is imperative that all efforts be made to clean up the environment starting with one of the most dangerous mineral pollutants: asbestos. This job requires extensive interdisciplinary cooperation and the establishment of an unambiguous interdisciplinary language. The extensive list of definitions offered in the recent U.S. Bureau of Mines Information Circular [10] are comprehensive and consistent with mineralogical traditions. The adoptation of these definitions for the interdisciplinary language of asbestos studies should be considered. The following definitions of the four most critical asbestos-related mineralogical terms are based on their historical review. 13 0 w ~ 0 A Go ,.r U

FIBER An acicular single crystal, or a similarly elongated polycrystalline aggregate, which displays some resemblance to organic fibers. Examples for criteria of "resemblance to organic fibers" are: circular cross section, `flexibility, silky surface luster, axial lineation, threaded appearance, etc. Most of these fiber characteristics cannot be observed at electron-microscopic scale. Consequently, any elongated particle may be called a fiber (when fiber used as a shape-descriptive expression) provided that it displays parallel edges and apparently equidimensional cross section. That is, elongated triangular-shaped or irregular particles cannot be considered to have the shape of a fiber. FIBROUS The descriptive term used for a mineral which is composed of parallel, radiating or interlaced aggre9ates offbers, from which the fibers are usually separable. That is, the crystalline aggregate may be referred to as fibrous even if it is not composed of separable fibers, but has that distinct appearance. ASBESTIFORM A special type of fibrous habit in which the fibers are separable, and are more flexible and osp sess higher tensi~ strength than crystals in other habits of the same mineral. Increased flexibility and higher tensile strength are, apparently, the most distinct qualities of asbestiform fibers. These properties are undoubtedly due to certain structural variations and can justifiably be included in the definition. ASBESTOS A collective mineralo ical term which includes the asbestiform varieties of various si icate minerals. lT•T$ - The justification for restricting asbestos to silicate minerals may be questionable from the mineralogical point of view, as non-silicate minerals may also crystallize in fibrous habit and the fibers may possess asbestiform properties. However, these properties are expected to be different in magnitude from those of the asbestiform silicates and, therefore, from the health study's point of view, are justifiably excluded from the category of asbestos. The dl nt of fibrous habits must be due to certain unusual conditions which existed at the time of the mineral's crystallization. These conditions may be accompanied by structural modifications and by consequent changes in the mineral's physical properties. These changes, however, are usually not as conspicuous as they are in silicate asbesti- form fibers. In fibrous gypsum, for example, the only readily observable change is in the mineral's fracture pattern. The usually absent ((111)) cleavage plane is perfect in fibrous gypsum and is responsible for its acicular rather than platy fragments. This change in the cleavage pattern is probably due to some structural modification. On the other hand, the conditions of crystallizations may be such that no change in the mineral's structure and properties is necessary. For example, if a fibrous mineral is altered to another, the new mineral may show pseudomorphic fibrous appearance. Dana [16, p. 678] believes that the appearance of fibrous talc is due to its alteration from enstatite. laThe industrial quality of asbestos depends, in part, on the degree of development of the asbestiform fiber structure in the mineral. That is, if more crystals have the scroll- like structure in chrysotile, or the crystals have higher density of defects or twinning in asbestiform amphiboles or have fewer surface defects, the asbestiform fibers are stronger and more flexible, and thus they are more desirable. A similar relationship may exist between the degree of development and the density of asbestiform fibers in the bundles, and their biological activity. That is, the gradation of asbestiform development in a mineral, from acicular cleavage fragments to asbestiform fibers, may constitute dif- ferent health hazards. , 14

The critical reviews offered by Drs. Edwin Roedder and James H. Stout are acknowledged with appreciation. This study was in part supported by a grant from the Regional Copper- nickel Study, Environmental Quality Council, Minnesota. References [1] Agricola, Georgius (Bauer), De Natura Fossilium, (Basilea, 1546). [2] Amosite discredited, Am. Mineral. 34, 339 (1946). [3] Berry, L. G. and Mason, Brian, Mineralogy, (Freeman and Co., San Francisco, 1959). [4] Beudant, F. S. , Traite Elementaire de Mineralogie, (Verdipre, Paris, 1824). [5] Blum, J. R. , Lehrbuch der Oryktognosie, (G. Schweizerbart, Stuttgart, 1833). [6] Boot, Anselmus Boetius, de, Gemmarum et Lapidum Historia, (Lugduni Bataborum, 1647). [7] Brard, C. P., Nouveau elemens de Mineralogie, 2e ed., (Meguinon-Marvis, Paris, 1824). [8] Bradt, R. C., Newnham, R. E. , and Biggers, J. V., The toughness of jade, Am. Mineral. 58, 727-732 (1973). [9] Bristow, H. W. , Glossary of Mineralogy, (Longman et al. , London, 1861). [10] Campbell, W. J., Blake, R. L., Brown, L. L., Cather, E. E., and Sjoberg, J. J., Selected silicate minerals and their asbestiform varieties; mineralogical definitionand identification-characterization, (U.S. Bureau of M nes. Int. Circ. No. 8751, 1977). [11] Champness, P. E., Lorimer, G. W., and Zussman, J., Fibrous cummingtonite in Lake Superior: Discussion, Canad. Mineral, 14, 394 (1976). [12] Chisholm, J. E., Planar defects in fibrous amphiboles, J. Material Sci. 8, 475-483 (1973). [13] Cloizeaux, A., des Manuel de Min€ralogie, 2 vols., (Dunond, Paris. 1862). [14] Cressey, B. A. and Zussman, J. , Electron microscopic studies of serpentinites, Canad. Mineral. 14, 307-313 (1976). , [15] Cronstedt, A. F., FBrsoktill en Mineralogie, eller Mineral Rikets Uppstdlning, (Stockholm, 1758). [16] Dana, Edward S., The System of Mineralogy of James Dwight Dana, Descriptive Mineralogy, 6th ed.,(J- . Wiley and Sons, New York, 1914)-. [17] Dana, James D., Manual of Mineralogy, (Henry H. Peck, New Haven, 1857, new ed. (1871). [18] Deer, W. A., Howie, R. A., and Zussman, J., Rock-Forming Minerals, 5 vols., (J. Wiley and Sons, 1962, 1963). [19] Delasse, A., (analysis of crocidolite) Compt. Rend. 44, 766 (1847). _ [20] Dioscorides, P., IIepl vans 1ezplKns (Materia Medica), (Approx. 50 A.D.). [21] Doelter, C., Handbuch des Mineralchemie, 3 vols., (T. Steinkopff, Dresden and Leipzig, 1912, 1914, 1918). [22] Drysdall, A. R. and Newton, A. R., Blue asbestos from Northern Rhodesia and its bearing on the genesis and classification of this type of asbestos, Am. Mineral. 45, 53-59 (1960). 15 2063104817

[23] Engleston, T., A Catalogue of Minerals and 5 ny onyms, (J. Wiley and Sons, New York, 1892). [24] Ford, W. E. , Dana's Textbook of Mineralogy, 4th ed., (J. Wiley and Sons, New York, 1951). [25] Franco, M. A., Hutchinson, J. L., Jefferson, 0. A., and Thomas, J. R., Structural imperfection and morphology of crocidolite (blue asbestos), Nature 266, 520-521 (1977). [26] Freiesleben, J. C., A. G. Werner's Letztes Mineral-System, (Craz and Gerold, Freyberg and Wien, 1817). [27] Gary, M. , McAfee, R. , Jr., and Wolf, C. L. , (editors), Glossary of Geology, (Am. Geol. Inst., Washington, D. C., 1972). [28] Great Lakes Research Advisory Board, Asbestos in the Great Lakes Basin, (February, 1975). [29] Groth, P., Tabellarische Ubersicht des Mineralien, 4te Aufl., (Friedrich Vieweg und Sohn, Braunschwe g, 1898 . [30] HaOy, M. L'Abbe, Traitd de Mineralogie, 5 vols., (Bachelier, Paris, 1801, 2e edition, 1822). [31] Hintze, C., Handbuch der Mineralogy, Bd. 2, (Von Veit, Leipzig, 1897). [32] Hodgson, A. A., Fibrous silicates, Lect. Ser. 1965 No. 4, (The Royal Inst. of Chem., 1966). [33] Hoffmann, C. A. S., Handbuch der Mineral6 ie, (after Bd. 2a by A. Breithaupt), 4 vals., (Craz and Gerold, Freyberg, 1811-1818 . [34] Hoffmann, C. A. S., (about Werner's Mineral System), 17th ed., 80rgm. 369 (1789). [35] Hurlbut, C. S., Jr., Dana's Manual of Mineralogy, (J. Wiley and Sons, New York, 1959). [36] Jameson, Robert, System of Mineralogv, (Archibald Constable, Edinburgh, 1816). [37] Jameson, Robert, Manual of Mineralogv, (Archibald Constable, Edinburgh, 1821). (38] Jones, R. H., Asbestos, its Properties, Occurrence and Uses, (Crosby Lockwood, London, 1890). [39] Kelly, A. and Nicholson, R. B., Strengthening Methods in Crystals, (Appl. Sci. Publ., London, 1971). [40] Kenngott, Adolf, Das Mohs'sche Mineral System, (C. Gerold, Wein, 1853). [41] Klockmann, F., Lehrbuch der Mineralogie, (F. Enke, Stuttgart, 1903). [42] Kramer, J. R. , Fibrous cuamingtonite in Lake Superior, Canad. Mineral. 14, 91-98 (1976). (43] Kraus, E. D., Hunt, W. F., and Ramsdell, L. S., Mineralogy, (McGraw-Hill, New York, 1959). [44] Kryvial, R. J., Wood, R. A., and Barrett, R. E., Identification and assessment of asbestos emissions from incidental sources of asbes os, (U.S. Eriv. Prot. Agency,: €PKTbT2-7 -iT,-WasTingtonep't. 19T4j- [45] Langer, A. M., Approaches and constraints to identification and quantitation of asbestos fibers, env. Health Presp. 9, 133-136 (1974). 16

Cia [46] Light, W. G. and Wei, E. T., Surface charge and asbestos toxicity, Nature 265, 537- 539 (1977). [47) Linneaus, C. A., 5 sy tema Naturae, (Holm, 1768). [48] ~Maser, M., Rice, R. V., and Mug, H. P., Chrysotile morphology, Am. Mineral. 45, 680-688 (1960). [49] Mohs, Frederich, GrUndriss der Mineralogie, 2 vols., (Dresden, 1822). English: Treatise on Mineralogy, Transl. by W. Haidinger, 2 vols., (Hurst and Robinson, London, 1825 . ' [50] Naumann, Carl F., Elemente der Mineralogie, 8te Aufl., (W. Engelmann, 1871). [51] Naumann, Carl F., Eiemente der Mineralogie, 13te Aufi. by Ferdinand Zirkel, (W. Engelmann, 1898). [52] Nicol, James, Elements of Mineralogy, (A. and C. Black, Edinburgh, 1873). [53] Peacock, M. A. , The nature and origin of the amphibole asbestos of South Africa, Am. Mineral. 13, 241-285 (1928). [54] Phillips, William, An Elementary Introduction to Mineralogy (1823), 4th ed. by R. Allan, (Longman, et al., London, 1837). [55] Plinius Secundus, C., Historia Naturalis, 27 books (77 A.D.) [56] Rammelsberg, C. F., Worterbuch des Chemischen Theils der Mineralogie, (C. G. Luderitz, Berlin, 1841). (57] Rammelsberg, C. F. , J. J. Berzelius' Neues Chemisches Mineral System (J. L. Schrag, NUrnberg, 1847). [58] Rogers, A. F. , Introduction to the Study of Minerals, (McGraw-Hill, New York 1937). [59] Scheerer, Th., (analysis of byssolite) POgg. Ann. 84, 389 (1851). [60] Schmidt, F. A., Mineralienbuch, (Krais and Hoffman, Stuttgart, 1855). [61] Thomson, Thomas, Outline of Mineralogy, Geology, and Mineral Analysis, 2 vols., (Baldwin and Cradock, London, 1836). [62] Tschermak, Gustav, Lehrbuch der Mineralogie, (Alfred Holder, Wein, 1884). [63] U.S. District Court, District of Minnesota, 5th Division, Supplemental Memorandum, (No. 5-72, Civil 19, Appendix 5, Judge Miles Lord, May 11, 1974). [64] Vermaas, F. H. 5., The amphibole asbestos of South Africa, Trans. Proc. Geol. Soc. South Africa 55, 199-229 (1952). [65] Walerius,I. A., Mineral-riket, (Hotm, 1847). [66] Werner, A. F. , Ausserlichen Kennzeichen des Fossilien, (Leipzig, 1774), English: On the external character ransl A. V. Carozzi (U of I11.. Press, 1962). [67] Whittaker, E. J. W., The structure of Bolivian crocidolite, Acta Crystallogr. 2, 312- 317 (1949). [68] Whittaker, E. J. W., The structure of chrysotile, Acta Crystallogr, 6, 747 (1953). [69] Wylie, A., Optical properties of asbestiform amphiboles and their non-asbestiform analogues, U.S. Bureau of Mines, I.R. (in press). 17 2063104819

C7 [70] Yada, Keiji, Study of chrysotile asbestos by a high resolution electron microscope, Acta Crystallogr. 23, 704-707 (1967). [71] Zoltai, T. and Stout, J. H., Comments on asbestiform and fibrous mineral fragments (Minn. Poll. Contr. Agency, 1935 W. Co. Road B-2, Roseville, MN 55113, 1976). [72] Zoltai, T., Veres, I., Wagner, M. J., and Hammer, R. F., Surface charges of asbestiform amphibole fibers, (in manuscript). Discussion M. COSSETTE: Could you tell me if the use of the word asbestoid implies that it is not quite asbestos? T. ZOLTAI: Brard and Beudant used it in lieu of asbestartich or asbestiform, that is, the expression is equivalent to asbestiform. A. BOHMER: Are you suggesting that if a mineral has an asbestiform habit in its varieties and it has a three-to-one ratio it is asbestos? That is, should we limit our classification of asbestiform to those minerals? ZOLTAI: Yes. 18