metamorphic
Serpentinite
Serpentinite (composed primarily of serpentine group minerals including antigorite, chrysotile, and lizardite)
Hardness: 3.5-6 on Mohs scale; Color: typically dark green, blackish-green, or mottled; Luster: waxy to greasy; Crystal structure: monoclinic; Cleavage: poor; Specific gravity: 2.5-2.6. Often feels slippery or soapy.
- Hardness
- 3
- Color
- typically dark green, blackish-green, or mottled
- Luster
- waxy to greasy
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Physical properties
Hardness: 3.5-6 on Mohs scale; Color: typically dark green, blackish-green, or mottled; Luster: waxy to greasy; Crystal structure: monoclinic; Cleavage: poor; Specific gravity: 2.5-2.6. Often feels slippery or soapy.
Formation & geological history
Formed through the hydration and metamorphic transformation of ultramafic rocks (like peridotite) from the Earth's mantle, typically at tectonic plate boundaries where seawater meets hot mantle rock.
Uses & applications
Used as decorative stone in architecture, for carvings (soapstone relative), historically as a source of asbestos, and as an industrial source of magnesium.
Geological facts
Serpentinite is the official state rock of California. It can contain magnetite, which makes some specimens slightly magnetic. It often creates unique soil conditions that support specialized endemic plant species.
Field identification & locations
Identify by its waxy luster, variety of green hues, and smooth, almost greasy feel. It is commonly found in ophiolite complexes along convergent plate boundaries (e.g., California Coast Ranges, Alps, Urals).
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