metamorphic
Weathered serpentinized ultramafic rock
Serpentinite; chiefly serpentine-group minerals, commonly with magnetite, brucite, talc, and relict olivine/pyroxene
AI-generated identification · may be incorrectTypically green to yellow-brown, mottled, waxy to dull, and massive; Mohs hardness about 2.5–4, with no consistent cleavage and specific gravity roughly 2.5–2.7. The strongly weathered, pitted surface and green coloration are characteristic, though exact identification would benefit from hardness, streak, and acid test…
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Physical properties
Typically green to yellow-brown, mottled, waxy to dull, and massive; Mohs hardness about 2.5–4, with no consistent cleavage and specific gravity roughly 2.5–2.7. The strongly weathered, pitted surface and green coloration are characteristic, though exact identification would benefit from hardness, streak, and acid tests.
Formation & geological history
Forms when mantle-derived peridotite is chemically altered by low-temperature, water-rich hydrothermal fluids, commonly along faults and tectonic plate boundaries. Its alteration may occur during ancient ocean-floor or subduction-zone processes; an exact geological age cannot be determined from the image.
Uses & applications
Used as decorative stone, carvings, countertops, and occasionally landscaping material; massive, attractive pieces have modest lapidary and collector interest. Fibrous asbestos-bearing varieties require careful handling and are unsuitable for cutting without testing.
Geological facts
Serpentinite often contains magnetite and may weakly attract a magnet; its green color reflects serpentine minerals. It is commonly associated with chromite, talc, and other ultramafic-rock minerals.
Field identification & locations
Look for greasy or waxy green surfaces, mottled veins, low hardness, and an absence of obvious quartz grains; a steel nail may scratch it. Common localities include California, the Appalachians, the Alps, New Zealand, and many ophiolite belts.
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