metamorphic
Serpentinite (likely serpentinized ultramafic rock)
Serpentinite, dominated by serpentine-group minerals (antigorite, lizardite, or chrysotile), commonly with magnetite and relict olivine/pyroxene
AI-generated identification · may be incorrectTypically dark green to gray-green, mottled, waxy to subvitreous, with pale fibrous or granular patches; hardness about 2.5–4 Mohs and specific gravity roughly 2.5–2.7. The rounded specimen appears polished or naturally worn, so cleavage and original texture are partly obscured.
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Physical properties
Typically dark green to gray-green, mottled, waxy to subvitreous, with pale fibrous or granular patches; hardness about 2.5–4 Mohs and specific gravity roughly 2.5–2.7. The rounded specimen appears polished or naturally worn, so cleavage and original texture are partly obscured.
Formation & geological history
Forms when mantle-derived peridotite is hydrated and metamorphosed during tectonic alteration, especially along oceanic crust and subduction zones. Formation ages vary widely, from Precambrian to modern tectonic settings.
Uses & applications
Used as decorative stone, countertops, carvings, and historically as a source of asbestos-bearing material; attractive pieces are collected, though fibrous dust should not be generated.
Geological facts
Often shows a characteristic mottled ‘snake-skin’ pattern and may contain magnetite, giving some specimens weak magnetic response.
Field identification & locations
Common in ophiolites and fault zones, including California, Vermont, Italy, New Zealand, and the Urals. Confirm with a waxy green appearance, low hardness, and possible magnetism; the image alone cannot exclude chlorite-rich schist or altered basalt.
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