metamorphic
Tumbled serpentinite (likely)
Serpentinite; chiefly antigorite/lizardite/chrysotile, Mg3Si2O5(OH)4, with accessory magnetite and possibly chromite
AI-generated identification · may be incorrectDark bluish-green to gray, mottled and waxy to subvitreous, with irregular lighter veins and sparkly granular areas; typically Mohs 2.5–4, massive rather than visibly crystalline, with poor cleavage and specific gravity about 2.5–2.7.
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Physical properties
Dark bluish-green to gray, mottled and waxy to subvitreous, with irregular lighter veins and sparkly granular areas; typically Mohs 2.5–4, massive rather than visibly crystalline, with poor cleavage and specific gravity about 2.5–2.7.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during seafloor spreading or subduction; most specimens are Paleozoic to Cenozoic, though serpentinite occurs in rocks of many ages.
Uses & applications
Used as ornamental stone, carvings, beads, tumbled stones, and occasionally countertops or building stone; attractive material has modest lapidary value.
Geological facts
The green color comes from serpentine-group minerals, while dark grains may be magnetite or chromite. Some serpentinite can contain trace asbestos-form chrysotile, so avoid generating dust when cutting or grinding.
Field identification & locations
Identify it by its green-gray mottling, smooth waxy feel, relatively low hardness, and occasional magnetic response; common in ophiolites and tectonic belts, including California, Italy, New Zealand, and Canada. The image is consistent with serpentinite but cannot confirm locality or exact mineralogy.
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