metamorphic
Polished greenstone (likely nephrite jade)
Nephrite, a fibrous aggregate of tremolite–actinolite amphibole: Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂
AI-generated identification · may be incorrectDark green to black-green, waxy to silky luster, very tough and fine-grained; Mohs hardness about 6–6.5, no visible cleavage, specific gravity roughly 2.9–3.1. The smooth surface indicates polishing or natural water wear.
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Physical properties
Dark green to black-green, waxy to silky luster, very tough and fine-grained; Mohs hardness about 6–6.5, no visible cleavage, specific gravity roughly 2.9–3.1. The smooth surface indicates polishing or natural water wear.
Formation & geological history
Forms by metamorphism and metasomatism of magnesium-rich rocks, commonly along serpentinite contacts; deposits range from ancient Precambrian to younger mountain-building events.
Uses & applications
Used for carvings, beads, ornaments, tools, and cabochons; quality depends on translucency, even color, texture, and absence of fractures.
Geological facts
Nephrite is one of the two materials historically called jade, the other being jadeite. Its interlocking amphibole fibers give it exceptional resistance to breakage.
Field identification & locations
Common sources include British Columbia, New Zealand, Siberia, China, Wyoming, and Taiwan. Confirm with hardness, density, microscope examination, and laboratory testing; green serpentine and other stones can look similar.
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