metamorphic
Serpentinite (likely brecciated serpentinite)
Serpentinite; primarily serpentine-group minerals (antigorite, lizardite, chrysotile), commonly with magnetite, brucite, and relict olivine/pyroxene
AI-generated identification · may be incorrectDark green to black, mottled and rough, with a waxy to dull luster; typically Mohs 2.5–4, variable cleavage, and relatively high specific gravity (~2.5–2.7). The specimen appears brecciated, with angular lighter fragments in a green serpentinized matrix.
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Physical properties
Dark green to black, mottled and rough, with a waxy to dull luster; typically Mohs 2.5–4, variable cleavage, and relatively high specific gravity (~2.5–2.7). The specimen appears brecciated, with angular lighter fragments in a green serpentinized matrix.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite undergo hydration during low-temperature metamorphism, commonly along faults and oceanic crust; ages vary widely from Precambrian to modern tectonic settings.
Uses & applications
Used as decorative dimension stone, carvings, aggregate, and historically as a source of asbestos where chrysotile is present; attractive pieces are collected, though fibrous material should not be cut or abraded.
Geological facts
Serpentinite often preserves ghostly textures of former olivine and pyroxene and may contain magnetite, making some specimens weakly magnetic.
Field identification & locations
Common in ophiolites and tectonic mélange zones, including California, the Appalachians, New Zealand, Italy, and Cyprus. Confirm with a waxy green appearance, low hardness, and possible magnetism; exact identification may require microscopy or XRD.
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