metamorphic
Weathered green-gray stone, likely serpentinite or chlorite-rich metamorphic rock
Probable serpentinite (antigorite–lizardite), possibly chlorite schist or altered basalt
AI-generated identification · may be incorrectFine-grained, dull to faintly waxy luster, gray-green color, rounded by weathering; typical hardness is about 2.5–4 Mohs for serpentinite, with no visible cleavage or crystals. Exact identification requires testing for hardness, streak, density, and reaction to acid.
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Physical properties
Fine-grained, dull to faintly waxy luster, gray-green color, rounded by weathering; typical hardness is about 2.5–4 Mohs for serpentinite, with no visible cleavage or crystals. Exact identification requires testing for hardness, streak, density, and reaction to acid.
Formation & geological history
Likely formed when ultramafic mantle rock was hydrated during metamorphism, commonly in oceanic crust and subduction zones; ages vary widely from Paleozoic to recent tectonic exposures. The rounded shape indicates stream or surface weathering.
Uses & applications
Unusual pieces may be used as teaching specimens, landscaping stone, or low-grade carving material; attractive polished serpentinite is sometimes used decoratively. This small rough specimen has minimal commercial value.
Geological facts
Serpentinite commonly contains serpentine minerals and may include magnetite, chromite, or asbestos-form minerals; avoid cutting, sanding, or generating dust until identified. Its green color and smooth, soapy feel are characteristic.
Field identification & locations
Common in ophiolites and tectonic belts, including California, Italy, New Zealand, and the Appalachians. A steel nail may scratch it, while it generally will not scratch glass; a close photo cannot distinguish it confidently from altered basalt or chlorite-rich rock.
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