metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4
Hardness: 3-6 (variable), Color: Dark green to black with white speckles/veins, Luster: Waxy to greasy, Crystal structure: Monoclinic, Cleavage: Poor, Specific Gravity: 2.5-2.6
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Physical properties
Hardness: 3-6 (variable), Color: Dark green to black with white speckles/veins, Luster: Waxy to greasy, Crystal structure: Monoclinic, Cleavage: Poor, Specific Gravity: 2.5-2.6
Formation & geological history
Formed through serpentinization, an exothermic process where ultramafic rocks (like peridotite) from the Earth's mantle are hydrated and metamorphosed at low temperatures and high pressures near tectonic plate boundaries.
Uses & applications
Used as decorative architectural stone, in jewelry (often as a jade simulant), as a source of asbestos in the past, and for sculptures
Geological facts
Serpentinite is the official state rock of California. It can often contain trace amounts of chrysotile asbestos and is associated with unique soils that host rare plant species.
Field identification & locations
Identify by its characteristic 'snake-skin' appearance, dark green color, and waxy feel. Commonly found in ophiolite complexes and fault zones. Use a knife to check hardness; it is softer than quartz.
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