metamorphic
Serpentinite (likely)
Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄, with probable magnetite, carbonate, and altered olivine/pyroxene
AI-generated identification · may be incorrectDark gray-green, mottled and massive with a waxy to dull luster; typically Mohs 3–5.5, low-to-moderate density, poor visible crystal structure, and no prominent cleavage. The pale veining and rusty patches are consistent with alteration minerals and iron oxides.
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Physical properties
Dark gray-green, mottled and massive with a waxy to dull luster; typically Mohs 3–5.5, low-to-moderate density, poor visible crystal structure, and no prominent cleavage. The pale veining and rusty patches are consistent with alteration minerals and iron oxides.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite undergo hydrothermal hydration, commonly along oceanic crust and plate-boundary fault zones. Individual alteration events may range from Paleozoic to Cenozoic, depending on locality.
Uses & applications
Used as decorative stone, carving material, aggregate, and occasionally architectural facing; historically used for stone objects. Collector value is usually modest unless the specimen has exceptional color, polished patterns, or associated minerals.
Geological facts
Serpentinite can contain chrysotile, a fibrous asbestos mineral, so avoid cutting, grinding, or creating dust. Magnetite may make some pieces weakly magnetic.
Field identification & locations
Field clues include a greenish-gray color, greasy or waxy surface, irregular pale veins, and unusually soft, massive texture. Common occurrences include California, Italy, New Zealand, Canada, and the Appalachian and Alpine belts; confirm with hardness, streak, density, and laboratory testing.
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