metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)3Si2O5(OH)4
Hardness: 3-6 (Mohs scale), Color: dull green to deep blackish-green, Luster: waxy or greasy when polished, Structure: massive or fibrous, Cleavage: poor, Specific Gravity: 2.2-2.9. This specimen shows a smooth, river-worn or beach-worn texture.
Identified More metamorphic →
Explore Serpentinite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3-6 (Mohs scale), Color: dull green to deep blackish-green, Luster: waxy or greasy when polished, Structure: massive or fibrous, Cleavage: poor, Specific Gravity: 2.2-2.9. This specimen shows a smooth, river-worn or beach-worn texture.
Formation & geological history
Formed by the low-temperature hydrothermal alteration of ultramafic rocks (like peridotite) from the Earth's mantle, a process known as serpentinization. This typically occurs at tectonic plate boundaries or mid-ocean ridges.
Uses & applications
Used as a decorative stone in architecture (terrazzo), as a source of magnesium, historically for asbestos (in fibrous varieties), and currently popular for sculpture and jewelry (California jade).
Geological facts
Serpentinite is the official state rock of California. It is often found in 'ophiolite sequences' which are slivers of ocean floor thrust onto continents. It creates unique, nutrient-poor soil that supports endemic plant species.
Field identification & locations
Identify in the field by its characteristic 'serpentine' green color and greasy feel. Look for it in areas of high tectonic activity or subduction zones. Common in California, Cornwall (UK), and New Zealand.
More like this
