metamorphic
Serpentinite (likely polished/tumbled)
Serpentinite; chiefly serpentine-group minerals, commonly antigorite, lizardite, and chrysotile, with magnetite and accessory carbonates
AI-generated identification · may be incorrectUsually dark green to black with pale green, cream, or yellow veining; waxy to subvitreous luster and massive texture. Hardness is about 2.5–4 Mohs, with poor cleavage and variable specific gravity around 2.5–2.6; this specimen may also contain harder quartz or carbonate patches.
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Physical properties
Usually dark green to black with pale green, cream, or yellow veining; waxy to subvitreous luster and massive texture. Hardness is about 2.5–4 Mohs, with poor cleavage and variable specific gravity around 2.5–2.6; this specimen may also contain harder quartz or carbonate patches.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite hydrate during low-temperature metamorphism, commonly along faults and plate boundaries. Serpentinization is generally Phanerozoic, though the host rocks can be much older.
Uses & applications
Used as ornamental stone, carvings, countertops, and historically as a source of magnesium and asbestos-bearing material. Attractive polished pieces are collected as lapidary specimens.
Geological facts
Its mottled “snake-skin” appearance and contrasting veining are characteristic. Chrysotile-bearing serpentinite can release hazardous fibers when cut or abraded, so avoid sawing or making dust without proper controls.
Field identification & locations
Identify it by its low hardness, greasy or waxy feel, dark green-black color, and patchy veining; it commonly occurs in ophiolites and mountain belts. Common localities include California, Italy, New Zealand, Canada, and Afghanistan.
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