metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni)3Si2O5(OH)4
Hardness: 3-6 (variable), Color: Shades of green, yellowish-green to black, Luster: Greasy, waxy, or silky, Crystal structure: Monoclinic, Cleavage: Poor, Specific Gravity: 2.5-2.6
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Physical properties
Hardness: 3-6 (variable), Color: Shades of green, yellowish-green to black, Luster: Greasy, waxy, or silky, Crystal structure: Monoclinic, Cleavage: Poor, Specific Gravity: 2.5-2.6
Formation & geological history
Formed through the hydration and metamorphic transformation of ultramafic rocks (like peridotite) from the Earth's mantle at low temperatures and high pressures, often in subduction zones.
Uses & applications
Used as decorative architectural stone, in jewelry (often called 'New Jade'), as a source of magnesium, and historically as fire-resistant material.
Geological facts
Serpentinite is the state rock of California. It can contain asbestos minerals and is often associated with unique ecosystems because of its low nutrient and high heavy metal content.
Field identification & locations
Identify in the field by its distinctive green color, soapy or waxy feel, and its association with fault zones and oceanic crust. Common in the Coast Ranges of California, Italy, and Greece.
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