metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)3Si2O5(OH)4
Hardness: 3-6 (Mohs), Color: olive green to dark blackish-green, Luster: greasy, waxy, or silky, Crystal Structure: Monoclinic, Cleavage: Poor, Specific Gravity: 2.5-3.2, Texture: smooth to scaly.
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Physical properties
Hardness: 3-6 (Mohs), Color: olive green to dark blackish-green, Luster: greasy, waxy, or silky, Crystal Structure: Monoclinic, Cleavage: Poor, Specific Gravity: 2.5-3.2, Texture: smooth to scaly.
Formation & geological history
Formed at low temperatures through the hydration of ultramafic rocks (like peridotite) from the Earth's mantle, a process called serpentinization. Common in subduction zones and oceanic crust.
Uses & applications
Used as decorative building stone, in high-end carving and jewelry (sometimes as a jade stimulant), and historically as a source of asbestos and magnesium.
Geological facts
Serpentinite is the state rock of California. It can often contain trace amounts of asbestos and is known for producing poor, nutrient-deficient soils where only rare 'serpentine-endemic' plants can grow.
Field identification & locations
Identify by its characteristic 'snake-skin' green color and waxy feel. It is commonly found in mountain belts and along fault lines where deep crustal rocks have been pushed to the surface.
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