metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4
Hardness: 3-6 Mohs scale; Color: typically green (light to dark), greenish-black; Luster: waxy, greasy, or silky; Crystal Structure: Monoclinic; Cleavage: poor; Specific Gravity: 2.5-3.2
- Hardness
- 3-6 Mohs scale
- Color
- typically green (light to dark), greenish-black
- Luster
- waxy, greasy, or silky
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Physical properties
Hardness: 3-6 Mohs scale; Color: typically green (light to dark), greenish-black; Luster: waxy, greasy, or silky; Crystal Structure: Monoclinic; Cleavage: poor; Specific Gravity: 2.5-3.2
Formation & geological history
Formed through the hydration of ultramafic rocks (like peridotite) from the Earth's mantle, a process called serpentinization occurring at low temperatures and high pressures, often at tectonic plate boundaries.
Uses & applications
Used as an ornamental stone in architecture, for carvings (jewelry and figurines), and historically as a source of asbestos. High-quality varieties like 'Bowenite' are used as jade substitutes.
Geological facts
Serpentinite is the state rock of California. It often creates 'serpentine barrens' where the soil chemistry is so distinct (high magnesium, low calcium) that only specialized plants can grow there.
Field identification & locations
Identify by its characteristic waxy 'soapy' feel and green-mottled appearance resembling snakeskin. Commonly found in ophiolite complexes and subduction zones like the Coast Ranges of California or the Alps.
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