metamorphic
Serpentinite
Serpentinite (complex silicate mineral group (Mg,Fe)3Si2O5(OH)4)
Hardness: 3-6 (variable), Color: dark green to black with mottled patterns, Luster: waxy to greasy, Crystal structure: monoclinic (usually massive), Cleavage: poor, Specific Gravity: 2.5-2.6
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Physical properties
Hardness: 3-6 (variable), Color: dark green to black with mottled patterns, Luster: waxy to greasy, Crystal structure: monoclinic (usually massive), Cleavage: poor, Specific Gravity: 2.5-2.6
Formation & geological history
Formed by the hydration of ultramafic rocks (like peridotite) from the Earth's mantle through a process called serpentinization, typically at tectonic plate boundaries or subduction zones.
Uses & applications
Used as decorative stone in architecture, as a source of magnesium, historically for asbestos, and occasionally in jewelry as 'New Jade'.
Geological facts
Serpentinite is the state rock of California; it is often associated with unique ecosystems because the soil it produces is high in magnesium and heavy metals but low in essential nutrients.
Field identification & locations
Identify by its characteristic 'snake-skin' appearance, dark green mottled color, and slightly waxy feel. It is common in ophiolite complexes and coastal mountain ranges.
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