metamorphic
Serpentinite
Serpentinite, composed chiefly of serpentine-group minerals (antigorite, lizardite, chrysotile)
AI-generated identification · may be incorrectUsually dark green to gray-green with mottled or veined patterns, waxy to greasy luster, and a fine-grained massive texture; Mohs hardness is about 2.5–4, with poor cleavage and specific gravity around 2.5–2.6.
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Physical properties
Usually dark green to gray-green with mottled or veined patterns, waxy to greasy luster, and a fine-grained massive texture; Mohs hardness is about 2.5–4, with poor cleavage and specific gravity around 2.5–2.6.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are chemically altered by water during seafloor spreading or tectonic subduction. Most examples formed during ancient oceanic and plate-boundary processes, commonly from Paleozoic to Mesozoic rocks.
Uses & applications
Used as decorative stone, carvings, countertops, and ornamental aggregate; attractive polished pieces are collected, though chrysotile-bearing material should not be cut or powdered because of asbestos risk.
Geological facts
Its slick, mottled appearance commonly resembles reptile skin, inspiring the name. Black veins may contain magnetite, while pale patches can include carbonate minerals or talc.
Field identification & locations
Identify it by its green-black color, waxy surface, soft-to-moderate hardness, and abundant veining; common in ophiolites and subduction-zone mélanges, including California, Italy, New Zealand, and the Canadian Appalachians.
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