metamorphic
Tumbled greenstone (likely serpentinite or chlorite-rich metamorphic rock)
Serpentinite, commonly dominated by serpentine-group minerals; exact identification requires testing
AI-generated identification · may be incorrectDark olive-green, fine-grained, rounded and polished with a subdued waxy-to-satiny luster; serpentine has Mohs hardness 2.5–4 and no visible crystal structure or strong cleavage. The image alone cannot distinguish it confidently from chlorite schist, greenstone, or weathered basalt.
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Physical properties
Dark olive-green, fine-grained, rounded and polished with a subdued waxy-to-satiny luster; serpentine has Mohs hardness 2.5–4 and no visible crystal structure or strong cleavage. The image alone cannot distinguish it confidently from chlorite schist, greenstone, or weathered basalt.
Formation & geological history
Typically forms when ultramafic mantle rocks hydrate during metamorphism, often along tectonic plate boundaries and ophiolites; formation ages vary widely from Precambrian to recent tectonic settings.
Uses & applications
Used as decorative stone, carvings, beads, and small lapidary pieces; some serpentinite is quarried for architectural stone, though fibrous asbestos-bearing varieties require caution.
Geological facts
Serpentinite may show a greasy or waxy feel and can contain magnetite, producing weak magnetism. Avoid cutting or grinding unknown material because some varieties contain chrysotile asbestos.
Field identification & locations
Look for olive-green mottling, low hardness, waxy luster, and possible magnetism; a steel nail may scratch it, while vinegar usually produces little reaction. Common in California, Italy, New Zealand, Canada, and ophiolite belts worldwide.
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