metamorphic
Tumbled greenstone (likely serpentine or nephrite-like material)
Serpentinite, chiefly serpentine-group minerals; exact identification requires testing
AI-generated identification · may be incorrectTypically olive to dark green, mottled, waxy to subvitreous luster, fine-grained and massive; hardness about 2.5–5.5 Mohs, depending on composition. The rounded, polished surface obscures cleavage and texture; pale patches may be quartz, carbonate, or altered minerals.
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Physical properties
Typically olive to dark green, mottled, waxy to subvitreous luster, fine-grained and massive; hardness about 2.5–5.5 Mohs, depending on composition. The rounded, polished surface obscures cleavage and texture; pale patches may be quartz, carbonate, or altered minerals.
Formation & geological history
Usually forms when ultramafic mantle rocks are hydrated during metamorphism, commonly in ancient oceanic crust and subduction-zone environments. Serpentinization spans many geological ages, from Precambrian to modern tectonic settings.
Uses & applications
Used as a decorative stone, beads, carvings, tumbled specimens, and occasionally architectural stone; softer varieties are generally unsuitable for durable jewelry. Similar-looking nephrite jade is more valuable and harder.
Geological facts
Serpentine is a mineral group rather than one single mineral, with common species including antigorite, lizardite, and chrysotile. Some serpentinite contains magnetite and may weakly attract a magnet.
Field identification & locations
Common in tectonic mountain belts and ophiolites, including California, New Zealand, Italy, Canada, and the Ural region. A steel or glass scratch test, specific gravity, and refractive index help distinguish it from jade, epidote, and green jasper.
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