metamorphic
Polished serpentine-rich rock (likely serpentinite)
Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄, with possible magnetite, chlorite, and carbonate
AI-generated identification · may be incorrectTypically green to yellow-green, mottled, waxy to greasy luster, and fine-grained with no visible crystal faces; Mohs hardness about 2.5–4, commonly with irregular fracture and specific gravity around 2.5–2.6. The reddish-brown patches may be iron oxides or associated rock inclusions.
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Physical properties
Typically green to yellow-green, mottled, waxy to greasy luster, and fine-grained with no visible crystal faces; Mohs hardness about 2.5–4, commonly with irregular fracture and specific gravity around 2.5–2.6. The reddish-brown patches may be iron oxides or associated rock inclusions.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite hydrate during hydrothermal alteration, commonly along faults and oceanic crust; ages vary from ancient Precambrian occurrences to modern tectonic zones.
Uses & applications
Used as a decorative and carving stone, tumbled-stone material, countertops, and historically as a source of asbestos-bearing minerals; avoid cutting or abrading unknown specimens because some serpentinite contains chrysotile asbestos.
Geological facts
Its distinctive green color results from hydration and alteration of magnesium-rich minerals. It is often confused with jade, but is generally softer and less tough.
Field identification & locations
Common in convergent-margin and ophiolite belts, including California, Italy, New Zealand, and Canada; field clues are green mottling, waxy feel, low hardness, and occasional magnetism. A definitive identification requires microscopy or X-ray analysis.
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