metamorphic
Polished greenstone (likely serpentine)
Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄
AI-generated identification · may be incorrectDark green, smoothly polished, waxy to subvitreous luster, opaque, and massive rather than visibly crystalline; Mohs hardness about 2.5–4, with variable specific gravity around 2.5–2.6. The rounded shape appears tumbled or carved, so cleavage and crystal structure are not readily visible.
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Physical properties
Dark green, smoothly polished, waxy to subvitreous luster, opaque, and massive rather than visibly crystalline; Mohs hardness about 2.5–4, with variable specific gravity around 2.5–2.6. The rounded shape appears tumbled or carved, so cleavage and crystal structure are not readily visible.
Formation & geological history
Forms when magnesium-rich ultramafic rocks alter through hydrothermal metamorphism, commonly along tectonic plate boundaries; serpentinite bodies range from ancient Precambrian to geologically modern. The specimen has been shaped and polished by humans.
Uses & applications
Used for ornamental carvings, beads, cabochons, tiles, and decorative stone; historically mistaken for or marketed as jade. It is generally unsuitable for demanding construction applications because it is relatively soft and can contain asbestos-form minerals.
Geological facts
Serpentine is a mineral group, not one single mineral; its green color comes from iron and nickel-related impurities. Some varieties may contain chrysotile, a fibrous asbestos mineral, so avoid generating dust when cutting or grinding.
Field identification & locations
Identify by its dark mottled green color, low hardness, waxy feel, and inability to scratch glass reliably; a steel knife may scratch it. Common sources include California, Italy, New Zealand, Canada, and Zimbabwe, but laboratory testing is needed to distinguish it from nephrite jade or other green stones.
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