metamorphic
Nephrite Jade
Ca2(Mg, Fe)5Si8O22(OH)2 (Magnesium-rich Tremolite-Actinolite)
Hardness: 6.0–6.5 (Mohs scale); Color: Dark forest green to spinach green; Luster: Vitreous to greasy; Crystal structure: Monoclinic (fibrous aggregates); Cleavage: Indistinct; Specific gravity: 2.90–3.03.
- Hardness
- 6
- Color
- Dark forest green to spinach green
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 6.0–6.5 (Mohs scale); Color: Dark forest green to spinach green; Luster: Vitreous to greasy; Crystal structure: Monoclinic (fibrous aggregates); Cleavage: Indistinct; Specific gravity: 2.90–3.03.
Formation & geological history
Formed via contact metamorphism or hydrothermal alteration of mafic and ultramafic rocks (like serpentinite) or dolomitic limestones. It occurs in subduction zones where high pressure and low temperatures facilitate the interlocking of tremolite-actinolite crystals.
Uses & applications
Predominantly used for jewelry (beads, pendants), ornamental carvings, statues, and historical tools/weapons due to its extreme toughness/fracture resistance.
Geological facts
Nephrite is tougher than steel because of its felted, interlocking needle-like crystal structure. In ancient China, it was considered 'the Stone of Heaven' and symbolized immortality. It is the official state gemstone of Wyoming and Alaska.
Field identification & locations
Identify by its 'greasy' luster when polished, high density (heavy for its size), and extreme toughness (does not chip easily). It is commonly found in British Columbia, New Zealand, Russia, and the United States (Wyoming/California).
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