metamorphic
Serpentinite
Serpentine rock (Mg,Fe,Ni,Al,Zn,Mn)3(Si,Al,Fe)2O5(OH)4
Hardness: 3-6 Mohs. Color: Greenish-black, olive green, or yellow-green with mottled veins. Luster: Greasy, waxy, or silky. Crystal structure: Monoclinic. Cleavage: Poor. Specific Gravity: 2.5-3.2.
- Hardness
- 3-6 Mohs
- Luster
- Greasy, waxy, or silky
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Physical properties
Hardness: 3-6 Mohs. Color: Greenish-black, olive green, or yellow-green with mottled veins. Luster: Greasy, waxy, or silky. Crystal structure: Monoclinic. Cleavage: Poor. Specific Gravity: 2.5-3.2.
Formation & geological history
Formed by the low-temperature metamorphic hydration (serpentinization) of ultramafic rocks from the Earth's mantle, such as peridotite, often at tectonic plate boundaries/subduction zones.
Uses & applications
Used as decorative stone, for carving (sculptures), as a source of asbestos in the past, and as an industrial source of magnesium. High-grade specimens are used in jewelry.
Geological facts
Serpentinite is the official state rock of California. It can contain rare minerals and is often associated with the presence of 'serpentine barrens' where specific rare plants evolve to handle its high metal content.
Field identification & locations
Identify by its characteristic 'snake-skin' green mottled appearance and waxy feel. Common in ophiolite complexes, the Coast Ranges of California, and parts of the Appalachian Mountains.
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