metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)3(Si, Al, Fe)2O5(OH)4
Hardness: 3-6 Mohs. Color: Green, brownish-green, to black. Luster: Greasy, waxy, or silky. Structure: Fibrous or massive. Cleavage: Poor. Specific Gravity: 2.2-2.9.
- Hardness
- 3-6 Mohs
- Color
- Green, brownish-green, to black
- Luster
- Greasy, waxy, or silky
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Physical properties
Hardness: 3-6 Mohs. Color: Green, brownish-green, to black. Luster: Greasy, waxy, or silky. Structure: Fibrous or massive. Cleavage: Poor. Specific Gravity: 2.2-2.9.
Formation & geological history
Formed by the hydration and metamorphic transformation of ultramafic rocks (like peridotite) from the Earth's mantle, typically at tectonic plate boundaries or subduction zones.
Uses & applications
Used as decorative building stone, in sculptures, as a source for magnesium and asbestos (historically), and occasionally as a gemstone (variety lizardite or chrysotile).
Geological facts
Serpentinite is the official state rock of California. It is named for its resemblance to the skin of a snake and can contain minerals like magnetite, making some specimens slightly magnetic.
Field identification & locations
Identified by its distinctive green color, soapy or greasy feel, and smooth surfaces. Commonly found along fault lines, ophiolites, and mountain ranges like the Appalachians or the Mediterranean.
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