metamorphic
Serpentinite (likely serpentine-rich metamorphic rock)
Serpentine-group minerals, chiefly antigorite, lizardite, and/or chrysotile; commonly derived from altered peridotite
AI-generated identification · may be incorrectTypically olive-green to brownish green, mottled, waxy to dull or subtly silky luster, and massive rather than visibly crystalline. Hardness is usually 2.5–4 Mohs; cleavage is poor to absent, with specific gravity about 2.5–2.7.
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Physical properties
Typically olive-green to brownish green, mottled, waxy to dull or subtly silky luster, and massive rather than visibly crystalline. Hardness is usually 2.5–4 Mohs; cleavage is poor to absent, with specific gravity about 2.5–2.7.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during tectonic alteration, often along oceanic crust or subduction zones. Individual alteration ages vary widely, commonly from Paleozoic to younger tectonic events.
Uses & applications
Used as decorative stone, carvings, countertops, and sometimes jewelry; historically used as a source of asbestos where chrysotile is present. Avoid cutting, drilling, or generating dust unless asbestos content is ruled out.
Geological facts
The green color comes from iron- and magnesium-rich serpentine minerals, often with magnetite or minor chromite. Its rounded, smooth appearance is consistent with stream-worn serpentinite, though visual identification is not definitive.
Field identification & locations
Common in ophiolite belts and metamorphic zones, including California, the Appalachians, New Zealand, Italy, and Canada. A greasy/waxy feel, green mottling, low hardness, and lack of obvious grains support identification; laboratory testing is needed for certainty.
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