metamorphic
Serpentine
Serpentine-group (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4
Hardness: 3-6 on Mohs scale; Color: Yellowish-green to dark green, often mottled; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Poor; Specific gravity: 2.5-2.6
- Hardness
- 3-6 on Mohs scale
- Color
- Yellowish-green to dark green, often mottled
- Luster
- Greasy, waxy, or silky
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Physical properties
Hardness: 3-6 on Mohs scale; Color: Yellowish-green to dark green, often mottled; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Poor; Specific gravity: 2.5-2.6
Formation & geological history
Formed through serpentinization, an exothermic metamorphic process where ultramafic rocks (like peridotite) from the Earth's mantle are altered by low-temperature hydrothermal fluids.
Uses & applications
Commonly used for decorative carvings, architecture (green marble), jewelry-grade 'Williamsite', and was historically a source of asbestos.
Geological facts
Serpentine is the official state rock of California. It often contains inclusions of chromite or magnetite, which can make some specimens slightly magnetic.
Field identification & locations
Identify in the field by its distinctive 'snake-skin' appearance, greasy feel to the touch, and greenish hue. It is often found in ophiolite complexes near tectonic plate boundaries.
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