metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4
Hardness: 3-6 (Mohs scale), Color: dull to mottled green with light veining, Luster: waxy to greasy, Crystal structure: monoclinic (often fibrous or platy), Specific Gravity: 2.5-3.3
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Physical properties
Hardness: 3-6 (Mohs scale), Color: dull to mottled green with light veining, Luster: waxy to greasy, Crystal structure: monoclinic (often fibrous or platy), Specific Gravity: 2.5-3.3
Formation & geological history
Formed by the low-grade metamorphism of ultramafic rocks (like peridotite) from the Earth's mantle through a process called serpentinization, usually at tectonic plate boundaries or mid-ocean ridges.
Uses & applications
Used as a decorative stone in architecture (terrazzo, countertops), as a source of magnesium, historically for asbestos, and as a popular material for carving and jewelry.
Geological facts
Serpentinite is the official state rock of California. It often hosts unique ecosystems because the soil derived from it is high in heavy metals and low in essential nutrients.
Field identification & locations
Identify by its typically greasy or waxy feel, green mottled appearance, and susceptibility to being scratched by a steel blade. Commonly found in ophiolite complexes and subduction zones.
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