metamorphic
Weathered gray-green metamorphic rock, likely serpentinite or altered basalt
Serpentinite, chiefly serpentine-group minerals (antigorite/lizardite); identification is provisional from the photograph
AI-generated identification · may be incorrectFine-grained, rounded cobble with dull to weakly waxy luster, gray-green color, dark veins, and pits; typically Mohs 3–5, massive rather than visibly crystalline, with poor cleavage and specific gravity about 2.5–2.7.
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Physical properties
Fine-grained, rounded cobble with dull to weakly waxy luster, gray-green color, dark veins, and pits; typically Mohs 3–5, massive rather than visibly crystalline, with poor cleavage and specific gravity about 2.5–2.7.
Formation & geological history
Likely formed by hydration and alteration of ultramafic mantle rock during tectonic activity, commonly in ophiolites and fault zones; age depends on locality and may range from Paleozoic to modern tectonic settings.
Uses & applications
Serpentinite is used as decorative stone, carving material, aggregate, and historically as a source of asbestos-bearing minerals; attractive polished pieces are collected, though fibrous material should not be cut or abraded.
Geological facts
The rounded shape indicates stream or shoreline transport and weathering. Green coloration, a waxy surface, and black veining support serpentinite, but a chemical test or locality information is needed to distinguish it from altered basalt or chlorite-rich metamorphic rock.
Field identification & locations
Common in tectonically active belts and ophiolite complexes, including California, Oregon, Italy, New Zealand, and parts of Canada. Check for a greasy/waxy feel, low hardness, and possible white-green streak; avoid inhaling dust.
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