metamorphic
Serpentine
Serpentinite (group of hydrous magnesium iron phyllosilicate minerals, e.g., Lizardite, Antigorite)
Hardness: 3-6 Mohs (variable), Color: Pale to dark green (often mottled), Luster: Waxy to greasy, Crystal structure: Monoclinic, Cleavage: Poor, Specific Gravity: 2.5-2.6
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Physical properties
Hardness: 3-6 Mohs (variable), Color: Pale to dark green (often mottled), Luster: Waxy to greasy, Crystal structure: Monoclinic, Cleavage: Poor, Specific Gravity: 2.5-2.6
Formation & geological history
Formed at low temperatures and high pressures through the hydrothermal alteration of ultramafic rocks (like peridotite) containing olivine and pyroxene, typically at tectonic plate boundaries or seafloor spreading centers.
Uses & applications
Used for architectural cladding, decorative carvings, jewelry (as 'New Jade'), and historically as a source of asbestos. High-quality varieties are popular for lapidary arts.
Geological facts
It gets its name from its resemblance to the skin of a serpent. Serpentinite is the state rock of California and is often associated with unique ecosystems that support rare plant species due to its high magnesium and low calcium content.
Field identification & locations
Identify in the field by its distinctive green 'waxy' appearance, soapy feel, and relatively low hardness. It is commonly found in mountain belts (ophiolites) like the Coast Ranges of California or the Appalachian Mountains.
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