Abstract “Asbestos” is the general term applied to fibrous silicate minerals which are commercially valuable because they are resistant to heat and chemical attack and exhibit high tensile strength. Chrysotile is by far the most important asbestos mineral, accounting for more than 95% of consumption. The balance is made up by asbestiform varieties of amphibole, including riebeckite (variety crocidolite), cummingtonite (variety amosite), anthophyllite, tremolite, and actinolite. Almost all chrysotile is mined from vein deposits in serpentinized ultramafic rocks. A small amount is derived from either mass fibre deposits in serpentinitesor from serpentinized dolomites. This section deals only with deposits of chrysotile asbestos in serpentinized ultramafic rocks. The most important deposits in Canada include the Jeffrey mine at Asbestos, Quebec; the Bell-King-Beaver deposit at Thetford Mines, Quebec; the British Canadian and Black Lake mines at Black Lake, Quebec; the Asbestos Hill deposit in the Ungava region of Quebec; the Advocate mine at Baie Verte, Newfoundland; the Cassiar mine in British Columbia; and the Clinton Creek mine in Yukon Territory (Fig. 11-1). Important foreign deposits include Dzhetygara in Kazakhstan; Bazhenovo in Russia; Msauli in the Republic of South Africa; Havelock in Swaziland; Mang'ai in Qinghai, China; and Cana Brava in Goias, Brazil.