metamorphic
Polished greenstone pebble
Likely nephrite jade (tremolite–actinolite), though serpentine or greenstone is possible from appearance alone
AI-generated identification · may be incorrectOlive-green, opaque, finely textured, and waxy to vitreous when wet or polished; nephrite has Mohs hardness 6–6.5, tough interlocking fibers, no obvious cleavage, and specific gravity about 2.9–3.1. The rounded shape and glossy surface indicate natural water-worn or tumbled material.
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Physical properties
Olive-green, opaque, finely textured, and waxy to vitreous when wet or polished; nephrite has Mohs hardness 6–6.5, tough interlocking fibers, no obvious cleavage, and specific gravity about 2.9–3.1. The rounded shape and glossy surface indicate natural water-worn or tumbled material.
Formation & geological history
If nephrite, it formed by metamorphism of magnesium-rich rocks, commonly along tectonic boundaries; deposits range from Paleozoic to younger geological ages. Similar-looking serpentine forms through hydration of ultramafic mantle rocks.
Uses & applications
Used for carvings, beads, cabochons, ornaments, and tools; quality jade is valued in jewelry, while common polished pebbles have modest decorative value.
Geological facts
Nephrite is one of the two materials traditionally called jade, the other being jadeite. Its exceptional toughness—not merely hardness—made it valuable for prehistoric axes and blades.
Field identification & locations
Field tests include resistance to scratching by a steel knife, unusually high toughness, dense feel, and a fibrous texture under magnification; definitive identification requires specific gravity, refractive index, or laboratory analysis. Common sources include New Zealand, British Columbia, Wyoming, Siberia, and China.
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