metamorphic
Serpentinite pebble
Serpentinite, dominated by serpentine-group minerals (antigorite, lizardite, or chrysotile), commonly with magnetite and carbonate veins
AI-generated identification · may be incorrectDark greenish-black, fine-grained, waxy to slightly greasy luster with pale veining; Mohs hardness about 2.5–4, typically massive rather than visibly crystalline, with poor cleavage and specific gravity around 2.5–2.7.
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Physical properties
Dark greenish-black, fine-grained, waxy to slightly greasy luster with pale veining; Mohs hardness about 2.5–4, typically massive rather than visibly crystalline, with poor cleavage and specific gravity around 2.5–2.7.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite hydrate during low-temperature metamorphism, often near tectonic plate boundaries and subduction zones; ages range from Precambrian to modern tectonic settings.
Uses & applications
Used as decorative stone, landscaping material, carvings, and occasionally countertops; attractive polished pieces are collected, though chrysotile-bearing material should not be cut or powdered because of asbestos risk.
Geological facts
The pale veins are commonly magnesite, calcite, or fibrous serpentine. Serpentinite can feel unusually smooth or soapy and may contain magnetite, making some specimens weakly magnetic.
Field identification & locations
Identify by its dark green-black color, smooth waxy surface, light veins, low hardness, and possible magnetism; common in California, the Appalachians, New Zealand, Italy, and oceanic ophiolites. Image-based identification is provisional because similar basalt or slate can look alike.
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