metamorphic
Serpentinized ultramafic rock (likely serpentinite)
Serpentinite; chiefly antigorite/lizardite/chrysotile, commonly after peridotite (olivine–pyroxene)
AI-generated identification · may be incorrectTypically dark green to gray-green, waxy to greasy luster, massive and fine-grained, with slick or fibrous surfaces; Mohs hardness about 2.5–5.5 and specific gravity roughly 2.5–2.7. The specimen shows green matrix, brown weathering veins, and a strongly altered, fractured texture.
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Physical properties
Typically dark green to gray-green, waxy to greasy luster, massive and fine-grained, with slick or fibrous surfaces; Mohs hardness about 2.5–5.5 and specific gravity roughly 2.5–2.7. The specimen shows green matrix, brown weathering veins, and a strongly altered, fractured texture.
Formation & geological history
Forms when mantle-derived peridotite hydrates during low-temperature metamorphism, commonly along oceanic crust and tectonic plate boundaries. Serpentinization is generally Mesozoic to younger in exposed ophiolite belts, though the process can occur at any age.
Uses & applications
Used as decorative stone, carving material, aggregate, and historically as a source of asbestos where chrysotile is present; avoid cutting or sanding unknown material because fibers may be hazardous.
Geological facts
Serpentinite is often associated with chromite, magnetite, talc, and magnesite, and may have magnetic patches from magnetite formation.
Field identification & locations
Identify it by its green color, waxy feel, low hardness, and veined or slick appearance; common in California, the Appalachian Mountains, the Alps, New Zealand, and ophiolite complexes worldwide. A definitive identification requires hardness, streak, and thin-section or X-ray testing.
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