metamorphic
Serpentinite
Serpentinite (composed primarily of Serpentine group minerals like Antigorite, Lizardite, and Chrysotile)
Hardness: 3-6 Mohs. Color: Greenish-gray to dark green, sometimes with black or light mottling. Luster: Greasy, waxy, or dull. Crystal structure: Fibrous or platy (microcrystalline). Cleavage: Poor to none (massive). Specific Gravity: 2.5-2.6.
- Hardness
- 3-6 Mohs
- Luster
- Greasy, waxy, or dull
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Physical properties
Hardness: 3-6 Mohs. Color: Greenish-gray to dark green, sometimes with black or light mottling. Luster: Greasy, waxy, or dull. Crystal structure: Fibrous or platy (microcrystalline). Cleavage: Poor to none (massive). Specific Gravity: 2.5-2.6.
Formation & geological history
Formed through 'serpentinization,' a low-temperature metamorphic process where ultramafic rocks (like peridotite) from the Earth’s mantle are hydrated by seawater or hydrothermal fluids, typically at tectonic plate boundaries or subduction zones.
Uses & applications
Used as an ornamental stone in architecture, as a source for magnesium or asbestos (historical), and for sculpting. High-quality varieties are used as a substitute for jade.
Geological facts
Serpentinite is the official state rock of California. It can contain small amounts of rare minerals and is often associated with the presence of asbestos, though many specimens are safe to handle.
Field identification & locations
Identify by its characteristic 'snake-skin' green color, greasy feel, and association with fault zones. Commonly found in California, the Alps, and New Zealand. Look for a soapy texture when wet.
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