metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4
Hardness: 3-6 Mohs. Color: Green, yellowish-green, or grayish-green with dark wavy patterns. Luster: Greasy, waxy, or silky. Texture: Fine-grained to fibrous. Cleavage: Poorly defined. Specific Gravity: 2.2-2.9.
- Hardness
- 3-6 Mohs
- Luster
- Greasy, waxy, or silky
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Physical properties
Hardness: 3-6 Mohs. Color: Green, yellowish-green, or grayish-green with dark wavy patterns. Luster: Greasy, waxy, or silky. Texture: Fine-grained to fibrous. Cleavage: Poorly defined. Specific Gravity: 2.2-2.9.
Formation & geological history
Formed through serpentinization, a low-gradient metamorphic process where ultramafic rocks from the Earth's mantle are hydrated by hydrothermal fluids at subduction zones or mid-ocean ridges.
Uses & applications
Used as an ornamental stone in architecture, as a source of magnesium, and historically as a heat insulator. High-quality varieties like 'Bowenite' are used in jewelry.
Geological facts
Serpentinite is the official state rock of California. It often contains 'slickensides,' which are smooth, polished surfaces formed by movement along fault lines. It can also produce unique 'serpentine soils' that support rare endemic plant species.
Field identification & locations
Identify by its characteristic waxy 'serpentine' green color and soapy or slippery feel. Commonly found in ophiolite complexes and fault zones. Collectors should look for unique banding or chromium/magnetite inclusions.
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