Where Asbestos came from?

"White" asbestos 

Chrysotile, CAS No. 12001-29-5, is obtained from serpentine rocks. Chrysotile, along with other types of asbestos, have been banned in dozens of countries and is only allowed in the United States and Europe in very limited circumstances. Applications where Chrysotile might be used include the use of joint compound. There is no safe level of exposure to crysotile that is recognized. It is more flexible than amphibole types of asbestos; it can be spun and woven into fabric. Chrysotile does not persist in the lungs after inhalation; but is transferred to the pleura (the lining of the lungs) where mesothelioma, a fatal asbestos related cancer develops. Over 90% of the asbestos used in the United States is Chrysotile asbestos, making it one of the major causes of asbestos-related diseases in the U.S.

"Brown" asbestos 

Amosite, CAS No. 12172-73-5, is a trade name for the amphiboles belonging to the Cummingtonite - Grunerite solid solution series, commonly from Africa, named as an acronym from Asbestos Mines of South Africa. One formula given for Amosite is Fe₇Si₈O₂₂(OH)₂. This type of asbestos, like all asbestos, is very hazardous.

"Blue" asbestos 

Riebeckite, CAS No. 12001-28-4, also known under the variety name of Crocidolite, is an amphibole from Africa and Australia. It is the fibrous form of the amphibole riebeckite. Blue asbestos is commonly thought of as the most dangerous type of asbestos (see above and below). One formula given for Crocidolite is Na₂Fe²⁺₃Fe³⁺₂Si₈O₂₂(OH)₂. This type of asbestos is very hazardous.

Notes: chrysotile commonly occurs as soft friable fibers. Asbestiform amphibole may also occur as soft friable fibers but some varieties such as amosite are commonly straighter. All forms of asbestos are fibrillar in that they are composed of fibers with widths less than 1 micrometer that occur in bundles and have very long lengths. Asbestos with particularly fine fibers is also referred to as "amianthus". Amphiboles such as tremolite have a sheetlike crystalline structure. Serpentine (chrysotile) has a stringlike crystalline structure.(Inorganic Chemistry, E. de Barry Barnett and C. L. Wilson). Crysotile asbestos is often contaminated with tremolite, creating an additional hazard.

Other asbestos 

Other regulated asbestos minerals, such as tremolite asbestos, CAS No. 77536-68-6, Ca₂Mg₅Si₈O₂₂(OH)₂; actinolite asbestos (or smaragdite), CAS No. 77536-66-4, Ca₂(Mg, Fe)₅Si₈O₂₂(OH)₂; and anthophyllite asbestos, CAS No. 77536-67-5, (Mg, Fe)₇Si₈O₂₂(OH)₂; are less commonly used industrially but can still be found in a variety of construction materials and insulation materials and have been reported in the past to occur in a few consumer products.

Other natural and not currently regulated asbestiform minerals, such as richterite, Na(CaNa)(Mg,Fe⁺⁺)₅[Si₈O₂₂](OH)₂, and winchite, (CaNa)Mg₄(Al,Fe³⁺)Si₈O₂₂(OH)₂, may be found as a contaminate in products such as the vermiculite containing Zonolite insulation manufactured by W.R. Grace and Company. These minerals are thought to be no less harmful than tremolite, amosite, or crocidolite, but since they are not regulated, they are referred to as "asbestiform" rather than asbestos although may still be reltated to diseases and hazardous.

In 1989 the United States Environmental Protection Agency (EPA) passed the Asbestos Ban and Phase Out Rule which was subsequently overturned in the case of Corrosion Proof Fittings v. U.S. Environmental Protection Agency, 1991. This ruling leaves many consumer products that can still legally contain trace amounts of asbestos. For a clarification of products which legally contain asbestos visit the EPA's clarification statement. To be continued