metamorphic
Serpentine (likely greenstone)
Serpentine-group minerals, chiefly antigorite, lizardite, and chrysotile; commonly with magnesite or magnetite
AI-generated identification · may be incorrectTypically mottled apple- to olive-green, waxy to greasy luster, fine-grained and massive; Mohs hardness 2.5–4, specific gravity about 2.5–2.6, with poor cleavage. The rounded surface appears naturally weathered or possibly polished, and the gray-green patches may be host rock or alteration zones.
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Physical properties
Typically mottled apple- to olive-green, waxy to greasy luster, fine-grained and massive; Mohs hardness 2.5–4, specific gravity about 2.5–2.6, with poor cleavage. The rounded surface appears naturally weathered or possibly polished, and the gray-green patches may be host rock or alteration zones.
Formation & geological history
Forms when magnesium-rich ultramafic rocks such as peridotite are hydrated and metamorphosed during ocean-floor alteration or mountain-building, commonly from the Precambrian through the Cenozoic. This specimen may be associated with serpentinite mélange.
Uses & applications
Used as ornamental stone, carvings, beads, countertops, and historically as a jade substitute; massive serpentinite is also used locally as decorative aggregate. Fibrous chrysotile varieties are asbestos-bearing and require safe handling.
Geological facts
Serpentine is California’s state rock and commonly forms in tectonic zones where mantle rock reaches the surface. Green color results from iron and nickel-bearing serpentine minerals.
Field identification & locations
Identify by its low hardness, greasy feel, green mottling, and inability to scratch glass; a steel nail may scratch it. Common localities include California, New Zealand, Italy, Canada, and the Himalaya.
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