metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)3Si2O5(OH)4
Hardness: 2.5-5; Color: Dark green to black with mottled patches; Luster: Waxy, greasy, or silky; Crystal Structure: Monoclinic; Cleavage: Poor; Specific Gravity: 2.5-2.6.
- Hardness
- 2
- Color
- Dark green to black with mottled patches
- Luster
- Waxy, greasy, or silky
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Physical properties
Hardness: 2.5-5; Color: Dark green to black with mottled patches; Luster: Waxy, greasy, or silky; Crystal Structure: Monoclinic; Cleavage: Poor; Specific Gravity: 2.5-2.6.
Formation & geological history
Formed through serpentinization, an exothermic metamorphic process where ultramafic rocks (like peridotite) from the Earth’s mantle are hydrated by low-temperature water at tectonic plate boundaries.
Uses & applications
Used as decorative architectural stone, a source of magnesium, and historically as a source of asbestos. High-quality varieties are carved into figurines or jewelry.
Geological facts
Serpentinite is the official state rock of California. It often creates unique, nutrient-poor soils that support rare, endemic plant species that have evolved to tolerate high levels of heavy metals.
Field identification & locations
Identify in the field by its characteristic 'snake-skin' appearance, waxy texture, and dark green color. Often found in ophiolite complexes and subduction zones where oceanic crust meets continental crust.
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