Serpentine

Serpentine, common, widely distributed mineral, composed of hydrated magnesium silicate, Mg₃Si₂O₅(OH)₄, so called because of serpent-like bands of green colour occurring in massive varieties. It crystallizes in the monoclinic system and occurs in two distinct forms: antigorite, a massive variety, and chrysotile, a fibrous variety. The massive variety has a greasy, waxy lustre, and the fibrous variety is silky. Both varieties are coloured light and dark green, which in massive formations of antigorite produce a beautiful, variegated colouring. The term serpentine is also applied to a rock composed principally of antigorite. The hardness of the mineral ranges from 2 to 5, and the relative density ranges from 2.2 for chrysotile to 2.65 for antigorite. Chrysotile is the mineral from which asbestos is made. Antigorite, often used as an ornamental stone, sometimes occurs as a collateral mineral in verd antique marble.

Serpentine always occurs as an alteration product of another magnesium silicate mineral, such as olivine, amphibole, or pyroxene. Large deposits of chrysotile are located in Canada, in Russia, in Kazakhstan, in South Africa, and in Vermont, New York, New Jersey, and Arizona in the United States. It also occurs on the Lizard peninsula, Cornwall, England.