metamorphic
Serpentinite
Serpentinite (complex silicate mineral group (Mg,Fe)3Si2O5(OH)4)
Hardness: 3-6 Mohs. Color: Greenish-gray to dark green, sometimes with brownish patches. Luster: Greasy, waxy, or silky. Crystal structure: Fibrous or platy (microcrystalline). Specific gravity: 2.2-2.9. Texture: Smooth to slippery feel.
- Hardness
- 3-6 Mohs
- Color
- Greenish-gray to dark green, sometimes with brownish patches
- Luster
- Greasy, waxy, or silky
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Physical properties
Hardness: 3-6 Mohs. Color: Greenish-gray to dark green, sometimes with brownish patches. Luster: Greasy, waxy, or silky. Crystal structure: Fibrous or platy (microcrystalline). Specific gravity: 2.2-2.9. Texture: Smooth to slippery feel.
Formation & geological history
Formed through the hydrothermal metamorphic alteration of ultramafic rocks (like peridotite) from the Earth's mantle, typically at tectonic plate boundaries and subduction zones.
Uses & applications
Used as an ornamental stone, surfacing for roads, a source of magnesium, and historically as a source for asbestos (in specific varieties). High-grade versions are used for carvings and jewelry.
Geological facts
Serpentinite is the state rock of California. It is named for its resemblance to the skin of a serpent and often contains 'slickensides' – smooth, polished surfaces formed by movement along faults.
Field identification & locations
Identify by its characteristic green color, soapy or waxy feel, and common association with oceanic crustal sequences (ophiolites). Found in California, the Appalachian mountains, the Alps, and New Zealand.
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