Tremolite

Actinolite Amosite Anthophyllite Asbestos Asbestos, blue, 9 Asbestos, brown Asbestos, white, 9 Blue asbestos Blue asbestos (crocidolite), 9 Brown asbestos (amosite, mysorite), 9 Chrysotile Crocidolite Mysorite Talcum with tremolite and/or actinolite Tremolite White asbestos White asbestos (chrysotile, actinolite, anthophyllite, tremolite), 9 

Asbestos (1332-21-4) is the generic term used to describe over 30 different types of naturally occurring hydrated silicates representing two mineral groups (serpentine and amphiboles) that separate into fibres on mechanical processing. While the exact taxonomy continues to evolve, the sole serpentine variety is called chrysotile (12001-29-5) while the amphiboles include five forms  

White asbestos (12001-29-5) refers to the degree to which the mineral surface achieves complete reflectance over the visible spectrum rather than to the actual colour or hue of the mineral consequently, white describes multiple asbestos types, although it is most commonly applied to actinolite, chrysotile, and sometimes anthophyllite and tremolite. Similarly, while brown asbestos principally refers to amosite, it actually describes the degree to which the mineral deviates from colourlessness toward yellow, tan, or brown. 

Asbestos is resistant to heat, moisture, chemicals, microorganisms, wear, deformation, and decay and insulates against noise, heat, and electricity. It has been widely used commercially in fabrics, paper, filters, fillers, insulating boards, cements, fireproof garments, curtains, shields, brake linings, shingles, pipe coverings, and moulded products. 

Unfortunately, inhalation of asbestos fibres can lead to asbestosis, bronchogenic cancer, and mesothelioma. Other diseases and cancers have been reported, including those of the gastrointestinal tract. Less risk of exposure is presented by those products in which asbestos is embedded in a cement, plastic, asphalt, resin, mineral, or other binder in such a way that the fibres are only released and become airborne if the product is cut, abraded, damaged, or otherwise worked. 

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Purification of asbestos. Boil Gooch asbestos (tremolite, not chrysolite variety) with concentrated nitric acid, filter, wash free from acid, and dry at 100°. 

Talc of metasedimentary origin is formed by hydrothermal alteration of a dolomitic host rock by a silica-containing fluid. This type of deposit is typical of Montana and AustraUa. It is usually quite pure with talc content of 90 to 98% and often very white as well. Dolomite [17069-72-6], CaMg(C02)2, is the most common accessory mineral. The fourth type is of metamorphic origin, where a siUcaceous dolostone is first converted to tremolite [14567-73-8] or actinohte [13768-00-8] and then partially converted to talc. The Balmat, New York, and Death Valley, California, deposits are of this type. Tremolite, dolomite, and serpentine are common accessory minerals. This type of talc deposit has a variable talc content (30—80%), but is usually white and often commercially exploited because of the properties of its accessory minerals rather than the talc. 

Ceramics. In ceramics, talc is widely used in wall tile and hobbyware bodies, in electrical porcelains, and in cordierite formulations. Wall tile and hobbyware ate talc—clay bodies that ate pressed and fast-fired to a high porosity (bisque) and then glazed and tefired to produce the final product. Talc containing tremolite and carbonate is preferred to ensure good porosity. 

In the 1987 Regulations, asbestos is defined as any of the following minerals crocidolite, amosite, chrysotile, fibrous anthophyllite, fibrous actinolite, fibrous tremolite and any mixture containing any of these. Before carrying out work on any substance suspected of being asbestos, a competent person must be called to advise on its possible... 

Hydrothermal alteration minerals from midoceanic basalt are analcite, stilbite, heulandite, natrolite-mesolite-scolecite series, chlorite and smectite for zeolite facies, prehnite, chlorite, calcite and epidote for prehnite-pumpellyite facies, albite, actinolite, chlorite, epidote, quartz, sphene, hornblende, tremolite, talc, magnetite, and nontronite for green schist facies, hornblende, plagioclase, actinolite, leucoxene, quartz, chlorite, apatite, biotite, epidote, magnetite and sphene for amphibolite facies (Humphris and Thompson, 1978). 

The NIST material SRM 1866a consists of a set of three common bulk mine-grade asbestos materials chrysotile, amosite and crocidolite, and one glass filter sample. SRM 1867 consists of a set of three imcommon mine-grade asbestos materials antophyllite, tremolite and actinohte. The optical properties of SRMs 1866a and 1867 have been characterized so that they may serve as primary calibration standards for the identification of asbestos types in building materials. 

Mast, M. A., and J. I. Drever (1987), "The Effect of Oxalate on the Dissolution Rates of Oligoclase and Tremolite", Geochim. Cosmochim. Acfa51/9, 2559-2568. 

Figure 5,34 Effect of temperature on mean dimensions of various coordination polyhe-dra in tremolite C2lm). From Hawthorn (1981a). Reprinted with permission of The Min-eralogical Society of America.

Figure 5,35 Structure of tremolite projected on (001) plane. Dashed lines on [T40n] tetrahedral chains displacement (highly exaggerated for illustrative purposes) due to thermal decoupling. From Sueno et al. (1973). Reprinted with permission of The Mineralogi-cal Society of America.

The chemistry of many natural amphiboles is conveniently described by a compositional quadrilateral like that seen for pyroxenes. The quadrilateral components are anthophyllite [Mg7Sig022(0H)2], grunerite [Fe7Sig022(OH)2], tremolite [Ca2Mg5Sig022(OH)2], and ferro-tremolite [Ca2Fe5Sig022(OH)2] (figure 5.36). 

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