metamorphic
Nephrite Jade (River Cobble)
Nephrite (Silicate mineral: Ca2(Mg, Fe)5Si8O22(OH)2)
Hardness: 6-6.5 on Mohs scale. Color: Green, olive, or dark gray/black with possible iron staining. Luster: Greasy to waxy when wet. Crystal structure: Monoclinic, consisting of interlocking fibrous microcrystals which give it extreme toughness.
- Hardness
- 6-6
- Color
- Green, olive, or dark gray/black with possible iron staining
- Luster
- Greasy to waxy when wet
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Physical properties
Hardness: 6-6.5 on Mohs scale. Color: Green, olive, or dark gray/black with possible iron staining. Luster: Greasy to waxy when wet. Crystal structure: Monoclinic, consisting of interlocking fibrous microcrystals which give it extreme toughness.
Formation & geological history
Formed through the regional metamorphism of magnesium-rich rocks (ultramafic) or the interaction of fluids with dolomitic limestones. This specimen is a water-worn river cobble, likely eroded from a primary deposit and polished by long-term fluvial action.
Uses & applications
Commonly used for ornamental carvings, high-end jewelry (cabochons), and historically for tool and weapon making due to its extreme fracture resistance.
Geological facts
Nephrite is one of two distinct minerals referred to as 'Jade' (the other being Jadeite). It is famous for its 'toughness,' which is its resistance to breaking or chipping, making it even harder to break than diamond despite having a lower hardness score.
Field identification & locations
Identify in the field by looking for a 'waxy' appearance when wet, smooth water-worn texture, and high density. It will often feel heavy for its size. Common locations include British Columbia, Alaska, California, and New Zealand.
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