metamorphic
Serpentinite
Serpentinite (composed primarily of minerals in the Serpentine group)
Hardness: 2.5–5 on Mohs scale; Color: typically mottled shades of green, dark green, or black; Luster: greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: poor; Specific gravity: 2.5–2.6.
- Hardness
- 2
- Color
- typically mottled shades of green, dark green, or black
- Luster
- greasy, waxy, or silky
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Physical properties
Hardness: 2.5–5 on Mohs scale; Color: typically mottled shades of green, dark green, or black; Luster: greasy, waxy, or silky; Crystal structure: Monoclinic; Cleavage: poor; Specific gravity: 2.5–2.6.
Formation & geological history
Formed through the hydration and metamorphic transformation of ultramafic rock (peridotite) from the Earth's mantle. This process occurs at tectonic plate boundaries (subduction zones) and mid-ocean ridges.
Uses & applications
Used as decorative architectural stone, source of magnesium, historically used for asbestos (in specific fibrous varieties), and as a popular carving stone for sculpture.
Geological facts
Serpentinite is the official state rock of California. It is often called 'snake rock' because its mottled green patterns resemble snakeskin. It frequently creates unique ecosystems because its soils are low in nutrients but high in heavy metals.
Field identification & locations
Identify by its characteristic 'greasy' feel and mottled green coloring. It is commonly found in ophiolite complexes and fault zones. Collectors look for high-luster specimens or those with 'Slickensides' (polished surfaces from tectonic movement).
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