Asbestos is a group of fibrous
metamorphic minerals. The fibres are typically mixed with cement or woven into mats. It is used in buildings for its flame-retardant and insulating properties, its
tensile strength, flexibility, and its resistance to chemicals, but is now known to be
carcinogenic and is banned in many countries.
- Chrysotile[?], or white asbestos, is obtained from Canadian serpentine rocks. It is less friable, and therefore less likely to be inhaled, than the other types and is the type most often used industrially.
- Amosite[?], or brown asbestos, is an amphibole from Africa.
- Crocidolite[?], or blue asbestos, is an amphibole from Africa and Australia. It is the fibrous form of riebeckite[?].
Notes: Serpentine rocks are those with with curled fibres. Amphiboles have straight, needle-like fibres.
The amphiboles, in their fibrous form, are friable and therefore the most carcinogenic, although they also exist in safer non-fibrous forms.
Other asbestos minerals, such as tremolite[?], actinolite and anthophyllite[?] are not used industrially but occur in traces.
The fine particles released from asbestos fibres are easily inhaled, and can cause a number of respiratory complaints generally known as
asbestosis. This term includes
cancers of the throat, lungs and abdomen.
In the United States, asbestos was one of the first hazardous air pollutants regulated under Section 112 of the Clean Air Act of 1970.
See also: List of minerals, Eternit