Crocidolite composition

Two to 3 percent of the world s total asbestos production has been of the crocidolite variety, most of which has come from South Africa. Western Australia was a minor producer of crocidolite between 1944 and 1966. All amosite has been mined in the Transvaal Province of South Africa (2 to 3 percent of the world total). The only significant anthophyllite production came from Finland, where about 350,000 tons were mined between 1918 and 1966. Table 2.6 lists the composition, optical, and diffraction characteristics of the six asbestos minerals. More information on individual mineral species can be found in the references accompanying the sections on serpentine and amphibole types. Discussion of the geology, terminology, and exploitation of the several types of asbestos can be found in Ross (1981). 

Several amphiboles are fibrous and fibers from them can be processed to give heat-insulating materials. Among these are tremolite and crocidolite. These minerals are also used as fibers in composites. 

Asbestiform—Possessing the properties of asbestos. Minerals of specific chemical compositions can have asbestiform varieties that are fibrous in nature (e.g., crocidolite and amosite are the asbestiform varieties of the amphibole minerals, reibeckite and gmnerite tremolite and actinolite may be either asbestiform or nonasbestiform)... 

Muscovite and biotite have very similar compositions. Why is one "white mica" and the other "black mica" In the same vein, talc is white, chrysotile is while asbestos, crocidolite is blue asbestos and amosilc is a gray-bruwm asbestos. 

Natural erionite, synthetic nonfibrous zeolite with the composition of erionite, and crocidolite type asbestos were tested at a concentration of 10mg m inhalation in rats. Pleural mesotheliomas were found in 27 of 28 rats exposed to erionite one pulmonary and one pleural tumor were found in 28 rats exposed to synthetic zeolite, and one lung carcinoma was reported in rats exposed to crocidolite. 

The spectrum of a crocidolite (Fig. 10.23) having the composition (Nal.85Cao 14,Ko Ol)(Mgo 3oFe2.76Mno 04)(FC 93Alo 03)Si7 94.022(OH)2 34 can be analysed in terms of two Fe " " quadrupole doublets (AA, CC ) and one from Fe +(BB ). The fraction of Fe from the spectrum area is 0-41 which agrees with the chemical analysis. Crocidolite is an amphibole, and the spectrum assignment of AA to Mi sites, CC to M3 -f- (M2) sites, and BB to Fe in M2 sites is consistent with data from earlier studies on crocidolite and amosite, which also examined effects of oxidation and reduction [227, 228]. 

The serpentine form of asbestos, known as chrysotile, is mined chiefly in Canada and the former Soviet Union more than 90% of the asbestos used in the United States is in this form. The amphi-bole crocidolite is mined in small quantities, mainly in South Africa. The two minerals differ greatly in composition, color, shape, solubility, and persistence in human tissue. Crocidolite is blue, relatively insoluble, and persists in tissue. Its fibers are long, thin, and straight and they penetrate narrow lung passages. In contrast, chrysotile is white, and it tends to be soluble and disappear in tissue. Its fibers are curly they ball up like yarn and are more easily rejected by the body. Scientific studies of many types and by groups in many countries have shown that chrysotile asbestos is significantly less of a health hazard than other types. It is important to note that almost all manufactured materials in the United States contain only this form of asbestos. 

Muscovite and bioiite have very siirubr compositions. Why b one "while mka and Ihe other biuck mica In the same vein, lab is white, chrysolite k white asbestos, crocidolite is blue asbestos and amosile b a groy4>rown asbestos. 

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