metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4
Hardness: 3-6 Mohs; Color: Mottle green, olive green, to blackish-green; Luster: Waxy, greasy, or silky; Crystal Structure: Monoclinic; Cleavage: Poor/varied; Specific Gravity: 2.5-3.2.
- Hardness
- 3-6 Mohs
- Color
- Mottle green, olive green, to blackish-green
- Luster
- Waxy, greasy, or silky
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Physical properties
Hardness: 3-6 Mohs; Color: Mottle green, olive green, to blackish-green; Luster: Waxy, greasy, or silky; Crystal Structure: Monoclinic; Cleavage: Poor/varied; Specific Gravity: 2.5-3.2.
Formation & geological history
Formed through serpentinization, a metamorphic process where low-silica ultramafic rocks from the Earth's mantle are hydrated and chemically transformed at tectonic plate boundaries (subduction zones).
Uses & applications
Used in the past for heat-resistant materials (asbestos content), decorative building stone (terrazzo), jewelry (often as a jade substitute/New Zealand Greenstone), and as a source of magnesium.
Geological facts
Serpentinite is the official state rock of California. It often creates unique soil chemistry that supports rare or endemic plant species that can tolerate high magnesium and heavy metal levels.
Field identification & locations
Identify by its characteristic green color, waxy feel, and common association with fault zones. Often found in mountain belts such as the Appalachians, the Alps, and the California Coast Ranges.
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