metamorphic
Nephrite Jade
Nephrite (Ca2(Mg, Fe)5Si8O22(OH)2)
Hardness: 6.0-6.5 (Mohs scale); Color: Spinach green, olive green, grey-green; Luster: Vitreous to greasy; Crystal Structure: Monoclinic (fibrous/interlocking); Specific Gravity: 2.90-3.03; Cleavage: Indistinct
- Hardness
- 6
- Color
- Spinach green, olive green, grey-green
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 6.0-6.5 (Mohs scale); Color: Spinach green, olive green, grey-green; Luster: Vitreous to greasy; Crystal Structure: Monoclinic (fibrous/interlocking); Specific Gravity: 2.90-3.03; Cleavage: Indistinct
Formation & geological history
Formed through the regional metamorphism of magnesium-rich limestones (dolomite) or ultrabasic rocks. The characteristic toughness comes from an interlocking felt-like structure of fibrous crystals.
Uses & applications
Used extensively in jewelry, ornamental carvings, sculpture, and historically for durable tool-making (ax heads). High cultural value in China and New Zealand (Pounamu).
Geological facts
Nephrite was historically called 'Axe-stone' because of its extreme toughness, which makes it harder to break than diamond. It is one of two distinct minerals known as Jade, the other being Jadeite.
Field identification & locations
Identify by its greasy luster when polished and its extreme toughness (difficulty to scratch with steel). Common locations include British Columbia, New Zealand, Russia, and Wyoming, USA.
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