metamorphic
Tumbled serpentinized ultramafic rock
Serpentinite, chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), with probable quartz/calcite veins and iron oxides
AI-generated identification · may be incorrectDark olive-brown, polished/tumbled surface with waxy to dull luster and pale irregular veining; typically Mohs 2.5–4, fine-grained, massive, with no visible cleavage. Density is commonly about 2.5–2.6 g/cm³.
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Physical properties
Dark olive-brown, polished/tumbled surface with waxy to dull luster and pale irregular veining; typically Mohs 2.5–4, fine-grained, massive, with no visible cleavage. Density is commonly about 2.5–2.6 g/cm³.
Formation & geological history
Formed when mantle-derived peridotite undergoes hydration and low-temperature metamorphism, commonly in oceanic lithosphere and tectonic shear zones; ages vary from Precambrian to modern tectonic settings.
Uses & applications
Used as decorative stone, carvings, countertops, and lapidary material; attractive pieces are sold as worry stones or cabochons, though asbestos-bearing varieties require caution when cutting.
Geological facts
The specimen’s brown-green color and contrasting white veins are characteristic of serpentinization and later veining. Some serpentinite contains chrysotile asbestos, identifiable reliably only by testing.
Field identification & locations
Look for olive-green to brown color, waxy feel, low hardness, and pale veins; it may scratch with a steel knife and is often heavier than common glass. Common localities include California, Italy, New Zealand, Canada, and oceanic ophiolites.
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