Chrysotile

  Chrysotile is an asbestiform sub-group within the serpentine group of minerals. There are three known species of chrysotile: clinochrysotile (which is monoclinic), orthochrysotile (which is orthorhombic) and parachrysotile (which is also an orthorhombic polymorph). These varieties are all phyllosilicates. The chemical formulae for the three are the same: Mg₃(Si₂O₅)(OH)₄ with variable iron as Fe²⁺ substituting for magnesium. Chrysotile varies in color from gray-white to golden yellow to green. It has a hardness of 2.5 - 3. The three varieties form the fibrous members of the serpentine group and have been extensively mined as asbestos.

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  Clinochrysotile is the monoclinic form of chrysotile and likely the most common variety. Like the other two species of chrysotile (orthochrysotile and parachrysotile) it is very difficult to distinguish from the other species. Its type location is unknown although the chrysotile from Asbestos, Quebec, Canada is largely clinochrysotile.

Orthochrysotile is the orthorhombic form of chrysotile and is more common than the other orthorhombic form parachrysotile. Like the other two species of chrysotile (clinochrysotile and parachrysotile) it is very difficult to distinguish from the other species. Its type location is found in Silesia.

Parachrysotile is a second orthorhombic form of chrysotile. Like the other two species of chrysotile (orthochrysotile and clinochrysotile) it is very difficult to distinguish from the other species. Its type location is Québec, Canada.

Carcinogenity

Chrysotile, a mineral used for asbestos, is a human carcinogen, though there has been considerable debate over whether its potency approaches that of amphibole forms of asbestos. The question of whether "pure" chrysotile carries as great a risk as amphibole fibers is in any case largely academic, in that many chrysolite ore deposits do contain amphibole fiber asbestos such as tremolite, crocidolite and actinolite. Most commercial chrysotile in the US, for example, is contaminated with tremolite. Amphibole asbestos minerals have hard, needle-like fibers that penetrate into the lung tissue by piercing the walls of the alveoli. Since the body cannot dissolve or dispose of the amphibole fibers they cause a scarring of the lungs, called asbestosis, or cause a cancer of the lining (pleura) of the lung, called mesothelioma. Chrysotile fibers, on the other hand, are more likely to be dissolved or otherwise expelled by the body. The asbestos industry, notably in Canada, maintains that because chrysotile fibers are dissolved or expelled, they pose zero or minimal carcinogenic potential.

The one possible exception is non-friable (not damaged or capable of being crumbled by hand) vinyl flooring with 15% or less chrysotile content. A review of several studies of exposure levels to chrysotile during abatement of vinyl-chrysotile flooring found that very little airborne asbestos exposure occurs from this source. Considering the maximum exposure level found during all of the studies over a 40-year period, the review found a risk of asbestos-related diseases that was indistinguishable from zero (no risk). This conclusion applies only to non-friable chrysotile floor tiles and mastic, and not to damaged tiles, other forms of asbestos, or other uses of chrysotile.

References

• Webmineral
• Mindat clinochrysotile
• Mindat orthochrysotile
• Mindat parachrysotile
• Asbestos-containing Floor Tile and Mastic Abatement: Is there Enough Exposure to Cause Asbestos-related Disease?