Crocidolite Amphibole

Since ferrous iron usually colors minerals green, and ferric iron yellow or brown, it may seem rather remarkable that the presence of both together should give rise to a blue color, as in the case of vivianite. It may be pointed out, however, that this is by no means a unique instance of such an effect. Even apart from the artificial substances, Prussian and Turnbull s blues, which are complex cyanides containing both ferric and ferrous iron, there are several blue minerals in which the color seems explainable only on this basis. The most noteworthy of these are crocidolite and related amphiboles iolite and the blue tourmaline or indicolite. Other instances may perhaps be discovered, should this subject ever be investigated as it deserves to be . 

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). 

The initial connection between asbestos and mesothelioma was made by Wagner et al. (1960), when all but one patient in a study of mesothelioma-related deaths were found to be miners, workers, members of their families, or others living in the area of South Africa where the amphibole-asbestos crocidolite was mined. A comparable occupational exposure to crocidolite has been documented in Australia, with similar results (Armstrong et al., 1984). Mann and his associates (1966) documented three cases of mesothelioma among fifty-four patients dying of pulmonary asbestosis, and in two of the patients the mesotheliomas were peritoneal rather than pleural. 

Crocidolite This mineral name was originally proposed in 1831 for what was thought to be a distinct mineral, but was later shown to be a fibrous variety in the amphibole mineral series riebeckite-magnesioriebeckite. Crocidolite continues in trade use and, to some extent, in mineralogical and biomediccd scientific use. 

Crocidolite-asbestos A trade designation for a specific type of amphibole-asbestos composed of the mineral riebeckitc. It is also called blue asbestos and, if obtained from South Africa, may be labeled cape asbestos. 

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. 

Double-chain silicates. Double-chain silicates, (Si40n)n6n, are known as amphiboles, such as tremolite, Ca2Mg5(0H)2[(Si40n)2]. These include the true asbestoses, such as crocidolite or blue asbestos,... 

ASBESTOS. The tenn asbestos is a generic designation referring usually to six types of naturally occurring mineral fibers which are or have been commercially exploited, These fibers are extracted from certain varieties of hydrated alkaline silicate minerals comprising two families seipe.ntin.es and amphiboles. The serpentine group contains a single fibrous variety chrysotile five fibrous forms of amphiboles are known anthophyllite, amosite, crocidolite. tremolite, and actinolite... 

The fractional breakdown of the recent world production of the various fiber types shows that the industrial applications of asbestos fibers have now shifted almost exclusively to chrysotile. Two types of amphiboles, commonly designated as amosite and crocidolite are still being used, but their combined production is currently less than 2% of die total world production. The odier three amphibole varieties, anthophyllite, actinolite, and tremolite, have no significant industrial applications presently, This... 

CROCIDOLITE (Blue Asbestos). The mineral crocidolilc may be considered as u fibrous variety of the monoclinic amphibole. riebeckile. Ii is also known as a massive mineral. Iis hardness is 4 specific gravity, 3.2-3.3 luster, silky to dull color, blue or bluish-green. It is found in Austria, France. Bolivia, the Republic of South Africa (the variety known as tiger s-eye) and in the United States, in Massachusetts and Rhode Island. The name crocidolile is derived from the Greek, meaning to weave, in reference to its fibrous appearance. See also Uat s-Eye. 

Asbestos is the name given to a group of six different fibrous minerals (amosite, chrysotile, crocidolite, and the fibrous varieties of tremolite, actinolite, and anthophyllite) that occur naturally in the environment. One of these, namely chrysotile, belongs to the serpentine family of minerals, while all of the others belong to the amphibole family. All forms of asbestos are hazardous, and all can cause cancer, but amphibole forms of asbestos are considered to be somewhat more... 

It is important to recognize that asbestos is not a single substance, but is the generic name for a family of six related poly silicate fibrous minerals of which one (chrysotile) belongs to the serpentine family and five (actinolite, amosite, anthophyllite, crocidolite, and tremolite) belong to the amphibole family. These minerals differ from each other in physical and chemical properties, and each mineral can exist in a wide range of fiber sizes. These differences between fiber type and, more importantly, fiber size (length and diameter) are believed to be important determinants of the health risks posed by asbestos. 

Along these same lines, further work would be helpful in defining other fiber characteristics that are important determinants of carcinogenicity. It is suspected, for example, that amphiboles, such as crocidolite and tremolite asbestos, are more likely to cause mesothelioma than chrysotile, but it is not certain if this is attributable to differences in fiber length alone or to differences in chemical properties (e g., fiber morphometry, iron content, durability in biological fluids and tissues). Consequently, additional animal studies of the relative carcinogenic potency of airborne asbestos fibers of different types (e.g., chrysotile versus amphibole asbestos), carefully matched with regard to fiber size distribution, may be valuable. 

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)... 

Crocidolite— A type of asbestos in the amphibole group it is also known as blue asbestos. 

Regulatory agencies such as the U.S. Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) recognize six asbestos minerals chrysotile, a serpentine mineral and five amphibole minerals, actinolite asbestos, tremolite asbestos, anthophyllite asbestos, crocidolite asbestos, and amosite asbestos. Nonasbestiform amphibole minerals are not included in U.S. health regulations regarding asbestos because there is insufficient evidence that they will produce adverse health effects of the same type and severity produced by chronic exposure to asbestos. 

Tremolite asbestos has only rarely been found in commercially mined deposits. Some tremolite asbestos has been mined in South Africa, India, Maryland, and South Korea, but it has never been a nationally important commercial source of asbestos in the United States. (Ross 1981). The extent of tremolite asbestos mining was small in Powhatan and Pylesville, Maryland, where it occurs with anthophyllite asbestos in ultramafic rocks (Ross 1981). In South Africa, tremolite asbestos was mined in the early twentieth century, but most amphibole asbestos recently mined in South Africa is amosite or crocidolite... 

Fibers of amphibole asbestos such as tremolite asbestos, actinolite asbestos, and crocidolite are retained longer in the lower respiratory tract than chrysotile fibers of similar dimension. 

Economically important metamorphic minerals such as serpentine can affect health. In the past few years, asbestos removal has had significant impact on the cost of operating schools and other public buildings, hi the confusion over illness associated with asbestos made from the amphibole mineral crocidolite, citizens demanded the removal of all asbestos, unaware that a less-hazardous form of asbestos, the serpentine mineral chrysotile, also was removed at great expense. 

Synonyms Asbestos fiber Actinolite Amianthus Amosite Amphibole Anthophylite Ascarite Chrysotile Crocidolite Fibrous Grunerite Serpentine Tremolite... 

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