metamorphic
Serpentinite
Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), with possible magnetite, chlorite, and talc
AI-generated identification · may be incorrectTypically green to gray-green, mottled or veined, with a waxy to dull luster and fibrous, platy, or massive texture; Mohs hardness about 2.5–5.5. Cleavage is generally poor to indistinct, and specific gravity is commonly 2.5–2.6.
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Physical properties
Typically green to gray-green, mottled or veined, with a waxy to dull luster and fibrous, platy, or massive texture; Mohs hardness about 2.5–5.5. Cleavage is generally poor to indistinct, and specific gravity is commonly 2.5–2.6.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during low-temperature metamorphism, commonly along oceanic crust and fault zones. Specimen age depends on its source terrane, often Paleozoic to Mesozoic or younger.
Uses & applications
Used as decorative facing stone, carvings, countertops, and historically for ornamental objects; attractive specimens are collected. Chrysotile-bearing material should not be cut, crushed, or used where fibers may become airborne.
Geological facts
The green color results from serpentine minerals and alteration of iron- and magnesium-rich rocks. Serpentinite is California’s former state rock and commonly marks ancient oceanic lithosphere or subduction zones.
Field identification & locations
Identify it by its green mottling, slick or waxy surfaces, softness, and association with sheared ultramafic rocks; it may scratch easily with a knife. Common localities include California, Italy, New Zealand, Canada, and the Appalachian and Alpine belts.
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