metamorphic
Serpentinite
Serpentinite ((Mg,Fe,Ni,Al,Zn,Mn)3(Si,Al,Fe)2O5(OH)4)
Hardness: 3-6 Mohs. Color: mottled green, dark green, or black with waxy or silky luster. Crystal structure: Monoclinic (fibrous/massive). Specific gravity: 2.5-3.2. Surface often feels soapy or slippery.
- Hardness
- 3-6 Mohs
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Physical properties
Hardness: 3-6 Mohs. Color: mottled green, dark green, or black with waxy or silky luster. Crystal structure: Monoclinic (fibrous/massive). Specific gravity: 2.5-3.2. Surface often feels soapy or slippery.
Formation & geological history
Formed by the serpentinization (hydration and metamorphic transformation) of ultramafic rocks from the Earth's mantle, typically at tectonic plate boundaries/subduction zones.
Uses & applications
Used as an ornamental building stone (terrazzo, countertops), a source of magnesium, historically for asbestos production, and for carving or jewelry (as 'California Jade').
Geological facts
Serpentinite is the state rock of California. It often creates unique, nutrient-poor 'serpentine soils' that host rare endemic plant species. It is also significant in carbon sequestration research.
Field identification & locations
Identify by its green color, waxy luster, and slickensided (smooth, polished) surfaces. Commonly found in ophiolite complexes and tectonic suture zones like the California Coast Ranges or the Alps.
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