Chemical formula: Mg3[Si2O5](OH)4
Source: Quebec, California, Vermont, Soviet Union, and the Italian Alps
Chrysotile, also known as “white asbestos”, is one of three main members of the serpentine mineral group. The other two, lizardite and antigorite, although more abundant in nature are not regulated minerals. The serpentines are typically found in metamorphic rock.
Chrysotile is by far the most commonly used asbestos type and accounts for approximately 95% of asbestos found in U.S. buildings. In some asbestos mines the fibers are quite long making it conducive to weaving into fire and heat resistant textiles.
Chrysotile is a hydrous magnesium silicate. It has a layered structure. One layer has linked Silica tetrahedra Si2O5 which bind to a brucite Mg(OH)2 layer at the apical O and OH groups yielding an overall mineral chemistry of close to Mg3Si2O5(OH)4. Because of a mismatch in size of the two layers a curvature develops resulting in tightly wrapped concentric tubes. The resultant fibers are easily separated, strong, and very flexible. The unique internal structure aids in the identification of chrysotile. Although not as acid resistant as the other asbestos types, it has the highest tensile strength.
Chrysotile chemistry is fairly constant although there can be some substitution by Fe and Ni for Mg and Al for some Si. Magnesium replacement by Iron is small but common.
By Polarized Light Microscopy (PLM) chrysotile bundles typically appear curved or even wavy. A common occurrence is the presence of kinks or “knuckles” in the length of the bundle. The splayed or split ends of many bundles give a broomstick appearance. Chrysotile is monoclinic and has a positive sign of elongation. Its ? (gamma) refractive index value is less than 1.58. Individual fibers and even small bundles are beyond the resolution of light microscopy and TEM is often suggested to reduce the chance of false negatives or under estimation. By TEM, chrysotile fibrils display a characteristic internal tube structure and Electron Diffraction pattern, produced by the scrolling of chrysotile's curved sheets of tetrahedral and octahedral layers.
Spray-on insulation, asbestos cement, pipe and boiler insulation, brake linings, fire blankets and other fire proof and fire resistant textiles, roofing felts, mastics, putties and caulks, gaskets and ropes, transite panels and asbestos reinforced plastics (switchboards, insulation boards)