metamorphic
Tumbled greenstone (likely serpentine or nephrite-like material)
Serpentine-group minerals, commonly antigorite/lizardite; possibly nephrite jade (actinolite-tremolite)
AI-generated identification · may be incorrectOlive-green to yellow-green, smoothly polished, opaque, and waxy to dull luster; typically Mohs 2.5–4 for serpentine or 6–6.5 for nephrite. The rounded shape is human-tumbled; exact identification requires hardness, streak, density, and microscopic testing.
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Physical properties
Olive-green to yellow-green, smoothly polished, opaque, and waxy to dull luster; typically Mohs 2.5–4 for serpentine or 6–6.5 for nephrite. The rounded shape is human-tumbled; exact identification requires hardness, streak, density, and microscopic testing.
Formation & geological history
Serpentine forms when ultramafic mantle rocks undergo hydration and metamorphism; nephrite forms by metamorphic alteration involving magnesium-rich rocks. These materials range from ancient Precambrian to younger geological ages depending on locality.
Uses & applications
Used as decorative tumbled stone, carvings, ornamental objects, and—if confirmed nephrite—as jewelry and tools; serpentine is mainly a collector and architectural material.
Geological facts
The mottled olive coloration and waxy polish are characteristic of common serpentine-bearing stones, but appearance alone cannot distinguish serpentine from jade or other green rocks.
Field identification & locations
Look for black-green mottling, low-to-moderate weight, waxy texture, and variable translucency; a steel scratch test can separate softer serpentine from harder nephrite, though it may damage the specimen. Common sources include California, New Zealand, Canada, Russia, and China.
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