metamorphic
Tumbled dark green stone, likely serpentine
Serpentinite; chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄)
AI-generated identification · may be incorrectDark green to nearly black, waxy-to-greasy luster, massive and fine-grained with no visible crystals; Mohs hardness about 2.5–4, typically low density and poor cleavage. The photograph cannot confirm identity; nephrite jade, chlorite, or dark basalt are alternatives.
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Physical properties
Dark green to nearly black, waxy-to-greasy luster, massive and fine-grained with no visible crystals; Mohs hardness about 2.5–4, typically low density and poor cleavage. The photograph cannot confirm identity; nephrite jade, chlorite, or dark basalt are alternatives.
Formation & geological history
Usually forms when ultramafic mantle rocks undergo low-temperature hydration and metamorphism, commonly in oceanic crust and tectonic fault zones. Serpentinite ranges from ancient Precambrian bodies to modern ocean-floor occurrences.
Uses & applications
Carved ornaments, beads, countertops, and decorative stone; some varieties are marketed as “new jade.” Common tumbled pieces generally have modest value.
Geological facts
Serpentine may show mottled green patterns and can feel unusually smooth or soapy. Avoid generating dust from unknown serpentinite because some deposits contain asbestos-form minerals.
Field identification & locations
Commonly found in Alpine-type belts and ophiolites, including California, Italy, New Zealand, Canada, and Russia; a streak, hardness, density, and mineralogical test would help distinguish it from jade or basalt.
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