metamorphic
Polished gray-green stone, likely serpentine or nephrite jade
Serpentine-group minerals, chiefly antigorite/lizardite; possible nephrite (actinolite–tremolite amphibole)
AI-generated identification · may be incorrectOpaque to slightly translucent, mottled gray-green with brown iron staining and waxy-to-dull luster; typically massive rather than visibly crystalline. Hardness is about 2.5–5.5 for serpentine or 6–6.5 for nephrite; density roughly 2.5–3.0.
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Physical properties
Opaque to slightly translucent, mottled gray-green with brown iron staining and waxy-to-dull luster; typically massive rather than visibly crystalline. Hardness is about 2.5–5.5 for serpentine or 6–6.5 for nephrite; density roughly 2.5–3.0.
Formation & geological history
Serpentine forms when ultramafic rocks hydrate during metamorphism, while nephrite forms by metasomatic metamorphism involving magnesium-rich rocks. Ages vary widely by deposit.
Uses & applications
Used for carvings, beads, ornaments, and occasionally architectural stone; quality nephrite can be jewelry-grade, whereas common serpentine is inexpensive decorative material.
Geological facts
The rounded shape and surface gloss indicate tumbling or polishing. Visual identification cannot reliably distinguish serpentine from jade; hardness and laboratory tests are needed.
Field identification & locations
Common sources include China, New Zealand, Canada, Russia, Afghanistan, and the United States. Check streak, hardness, specific gravity, and fibrous texture; avoid acid testing unless necessary.
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