metamorphic
Weathered serpentinite (likely)
Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄, with possible magnetite, carbonate, and chromite
AI-generated identification · may be incorrectDark green-brown, mottled, earthy to waxy luster, irregular massive texture, and no obvious cleavage; hardness typically 2.5–4, though accessory minerals may be harder. The rusty coating reflects iron oxidation and weathering.
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Physical properties
Dark green-brown, mottled, earthy to waxy luster, irregular massive texture, and no obvious cleavage; hardness typically 2.5–4, though accessory minerals may be harder. The rusty coating reflects iron oxidation and weathering.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrothermally altered, commonly in oceanic crust and tectonic mélange zones. Formation ages vary widely, from ancient Precambrian bodies to younger oceanic rocks.
Uses & applications
Used decoratively as dimension stone, carvings, and collectible specimens; some varieties were historically used for ornamental objects. It is generally unsuitable for major construction where asbestos-forming minerals are present.
Geological facts
Serpentinite commonly contains magnetite, explaining occasional magnetic response, and may host chromite or nickel minerals. Chrysotile, a serpentine mineral, can occur and should not be cut, drilled, or powdered without testing.
Field identification & locations
Identify by green-black mottling, relatively soft/waxy surface, heavy massive form, and possible magnetism; a hardness, streak, acid, and asbestos-mineral test would improve certainty. Common in California, Italy, New Zealand, Canada, and convergent-plate belts.
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