metamorphic
Serpentinite
Serpentinite (composed primarily of Serpentine group minerals: (Mg,Fe)3Si2O5(OH)4)
Hardness: 3-6 on Mohs scale; Color: Green, brownish-green, or black; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Poor; Specific Gravity: 2.5-3.2. Often has a slick or soapy feel.
- Hardness
- 3-6 on Mohs scale
- Color
- Green, brownish-green, or black
- Luster
- Greasy, waxy, or silky
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Physical properties
Hardness: 3-6 on Mohs scale; Color: Green, brownish-green, or black; Luster: Greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: Poor; Specific Gravity: 2.5-3.2. Often has a slick or soapy feel.
Formation & geological history
Forms through the hydration and metamorphic transformation of ultramafic rocks (like peridotite) from the Earth's mantle, typically at tectonic plate boundaries (subduction zones).
Uses & applications
Used as decorative building stone, for carvings (sculptures), as a source of magnesium, and historically as a source of asbestos.
Geological facts
Serpentinite is the official state rock of California. The process of its formation, serpentinization, can release hydrogen and methane, potentially supporting microbial life in extreme environments.
Field identification & locations
Identify by its characteristic green color, mottled appearance, and waxy luster. Commonly found in ophiolite complexes and fault zones. Collectors should look for 'slickensides' (polished surfaces) on the rock.
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