metamorphic
Greenstone (likely serpentinite or chlorite-rich schist)
Serpentinite: Mg-rich phyllosilicates, chiefly antigorite/lizardite; possible chlorite-actinolite schist
AI-generated identification · may be incorrectOlive to gray-green, dull to waxy luster, fine-grained and foliated, with irregular fracture; hardness typically 2.5–4 Mohs and specific gravity about 2.5–2.7. The photograph alone cannot distinguish serpentinite from chlorite-rich schist confidently.
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Physical properties
Olive to gray-green, dull to waxy luster, fine-grained and foliated, with irregular fracture; hardness typically 2.5–4 Mohs and specific gravity about 2.5–2.7. The photograph alone cannot distinguish serpentinite from chlorite-rich schist confidently.
Formation & geological history
Formed when ultramafic mantle rock underwent hydration and metamorphism, or when magnesium-rich sediments/volcanics were metamorphosed. Ages vary widely, commonly Paleozoic to Mesozoic in exposed ophiolite belts.
Uses & applications
Used as decorative stone, carvings, aggregate, and occasionally jewelry; attractive polished pieces may be sold as serpentine or greenstone.
Geological facts
Serpentinite commonly contains magnetite and may be weakly magnetic; some varieties contain asbestos-form minerals, so avoid cutting, grinding, or generating dust.
Field identification & locations
Look for a greasy or waxy green surface, low hardness, dark veins, and possible foliation; a steel nail may scratch it. Common in tectonic suture zones and ophiolites, including California, New Zealand, Italy, and Appalachia.
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