ABSTRACT
The asbestos of commerce is a natural mineral fiber that is generally composed of chrysotile and/or asbestiform-amphibole. Positive identification of asbestos in geologic materials requires polarized light microscopy and/or powder X-ray diffractometry. Standard mineralogical techniques allow for the positive identification of geologic samples of asbestos minerals. Commercial deposits of asbestos are found in four types of rocks: banded ironstones, serpentinized peridotite rocks, stratiform ultramafic intrusions, and serpentinized limestone. Commercial asbestos is mined in a few localities with chrysotile, amosite, and crocidolite being the most important. Chrysotile fibers are very flexible, parallel in columnar growth, strong, easily separable, and with a silky luster. Chrysotile, a hydrous magnesium silicate of the serpentine group, has a layer type of structure. Major deposits of chrysotile occur in the southern Ural Mountains of the Soviet Union, southeastern Quebec, and the Italian Alps. The commercial deposits of chrysotile have generally formed in serpentinized peridotite in response to specialized geologic structures.
