Minerals (Category B)
Abestos, any of several minerals that readily separate into long, flexible fibres. Chrysotile, the fibrous form of the mineral serpentine, is the best-known type and accounts for about 95 percent of all asbestos in commercial use. It is a hydrous magnesium silicate with the chemical composition of Mg3Si2O5(OH)4. The other types all belong to the amphibole group of minerals and include the fibrous forms of anthophyllite, amosite (grunerite), crocidolite (riebeckite), tremolite, and actinolite. Though valued since ancient times for its resistance to fire, asbestos fibre did not achieve commercial importance until the 19th century. Modern asbestos production began in 1868 with the workings of a mine in Italy, and in 1878 large-scale production from deposits in Quebec began. Production slackened in the late 20th century owing to the health hazards posed by the mineral.