metamorphic
Tumbled dark green stone, likely serpentine or nephrite jade
Serpentine-group minerals, commonly antigorite/lizardite; possibly nephrite (interlocking tremolite-actinolite)
AI-generated identification · may be incorrectDark green to nearly black, waxy-to-subvitreous luster, rounded and polished, with pale green veining and surface fractures. Serpentine has Mohs hardness 2.5–4; nephrite is tougher and about 6–6.5; specific gravity is roughly 2.5–3.0. The photograph cannot reliably distinguish them.
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Physical properties
Dark green to nearly black, waxy-to-subvitreous luster, rounded and polished, with pale green veining and surface fractures. Serpentine has Mohs hardness 2.5–4; nephrite is tougher and about 6–6.5; specific gravity is roughly 2.5–3.0. The photograph cannot reliably distinguish them.
Formation & geological history
Serpentine forms when ultramafic mantle rocks hydrate during metamorphism; nephrite forms through metamorphic alteration of magnesium-rich rocks. These materials range from ancient Precambrian bodies to younger ophiolite and mountain belts.
Uses & applications
Used as ornamental stone, carvings, beads, cabochons, and decorative tumbled specimens; nephrite-quality material can be valuable jewelry stone, while ordinary serpentine is inexpensive.
Geological facts
The compact rounded form and dark green color are consistent with a polished/tumbled specimen, not a crystal. A steel scratch test can separate softer serpentine from harder jade, but it may damage the stone.
Field identification & locations
Common sources include California, British Columbia, New Zealand, Russia, China, and ophiolite belts worldwide. Value is typically $2–$15 for common tumbled serpentine and $20–$200+ for attractive or verified nephrite; exceptional jade is much higher.
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