metamorphic
Serpentinite
Serpentinite (composed primarily of Serpentine group minerals: (Mg,Fe)3Si2O5(OH)4)
Hardness: 3–6 on Mohs scale; Color: typically dark green to grayish-black with waxy streaks; Luster: greasy, waxy, or dull; Crystal structure: monoclinic; Cleavage: poor; Specific gravity: 2.5–2.6.
- Hardness
- 3–6 on Mohs scale
- Color
- typically dark green to grayish-black with waxy streaks
- Luster
- greasy, waxy, or dull
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Physical properties
Hardness: 3–6 on Mohs scale; Color: typically dark green to grayish-black with waxy streaks; Luster: greasy, waxy, or dull; Crystal structure: monoclinic; Cleavage: poor; Specific gravity: 2.5–2.6.
Formation & geological history
Formed through the hydration and metamorphic transformation of ultramafic rocks (like peridotite) from the Earth's mantle, typically at low temperatures and high pressures in subduction zones.
Uses & applications
Used as a source of asbestos in the past; currently used for decorative stone, architectural carvings, and as a source of magnesium.
Geological facts
Serpentinite is the state rock of California. It can contain small amounts of magnetite, making some specimens slightly magnetic, and it is frequently associated with rare minerals like jadeite.
Field identification & locations
Identify in the field by its characteristic 'snake-skin' appearance, dark green color, and slippery or waxy feel. Common in ophiolite complexes and tectonic plate boundaries.
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