metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4
Hardness: 3-6 (Mohs scale), Color: Dark green to yellowish-green with mottled appearance, Luster: Greasy or waxy, Crystal Structure: Monoclinic, Cleavage: Poorly developed, Specific Gravity: 2.5-3.2
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Physical properties
Hardness: 3-6 (Mohs scale), Color: Dark green to yellowish-green with mottled appearance, Luster: Greasy or waxy, Crystal Structure: Monoclinic, Cleavage: Poorly developed, Specific Gravity: 2.5-3.2
Formation & geological history
Formed through the serpentinization (metamorphic hydration) of ultramafic rocks from the Earth's mantle, such as peridotite, usually at low temperatures and high pressures near tectonic plate boundaries.
Uses & applications
Used as an ornamental stone for architectural finishing, sculptures, and occasionally as a source for magnesium or asbestos (in specific varieties). High-quality pieces are used in jewelry as 'Transvaal Jade'.
Geological facts
It is the state rock of California and often contains inclusions of chromite or magnetite. It is known for supporting unique, rare plant ecosystems in 'serpentine barrens' because of its high magnesium and low calcium content.
Field identification & locations
Identify by its characteristic waxy feel, green 'snake-skin' pattern, and softness compared to regular jade. Commonly found in ophiolite belts like the California Coast Ranges, the Alps, and the Himalayas.
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