metamorphic
Serpentine-rich altered rock (likely serpentinite)
Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄, with possible magnetite, talc, or chlorite
AI-generated identification · may be incorrectTypically olive-green to gray-green, waxy or greasy luster, fine-grained and massive; Mohs hardness about 2.5–4, with no obvious cleavage. The pictured pieces appear strongly weathered and may include darker magnetite-bearing material.
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Physical properties
Typically olive-green to gray-green, waxy or greasy luster, fine-grained and massive; Mohs hardness about 2.5–4, with no obvious cleavage. The pictured pieces appear strongly weathered and may include darker magnetite-bearing material.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated and metamorphosed, commonly along faults and oceanic crust; alteration can occur from the Precambrian to the present. Common worldwide in ophiolite belts and subduction zones.
Uses & applications
Used as ornamental stone, carvings, countertops, and historically as a decorative material; some varieties are collectible. Fibrous chrysotile-bearing specimens require caution because asbestos may be present.
Geological facts
Serpentinite often has a distinctive slick, mottled green appearance and may produce a white streak or feel unusually soapy. It can be weakly magnetic if magnetite formed during alteration.
Field identification & locations
Common in California, Oregon, Washington, Italy, New Zealand, Canada, and associated ophiolites worldwide; field confirmation requires hardness, streak, density, and thin-section or laboratory testing. Visual identification is provisional from the photo.
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