metamorphic
Dark green metamorphic rock, likely serpentinite
Serpentinite, composed mainly of serpentine-group minerals (antigorite, lizardite, or chrysotile), commonly with magnetite and minor chlorite/talc
AI-generated identification · may be incorrectFine- to medium-grained, mottled dark green-gray, with dull to waxy luster and irregular fracturing; serpentine hardness is about 2.5–4 Mohs, with a typical specific gravity near 2.5–2.6. The photograph does not show diagnostic crystal faces or cleavage clearly.
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Physical properties
Fine- to medium-grained, mottled dark green-gray, with dull to waxy luster and irregular fracturing; serpentine hardness is about 2.5–4 Mohs, with a typical specific gravity near 2.5–2.6. The photograph does not show diagnostic crystal faces or cleavage clearly.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite hydrate during hydrothermal alteration, commonly along oceanic crust, subduction zones, and major faults; ages range from Precambrian to modern tectonic settings.
Uses & applications
Used as decorative stone, carvings, lapidary material, and historically for architectural panels; fibrous chrysotile-rich varieties may contain asbestos and should not be cut or powdered.
Geological facts
Serpentinite is often associated with chromite, magnetite, talc, and occasionally jade-like green rocks. Its green color results from iron- and magnesium-rich serpentine minerals.
Field identification & locations
Look for a soft, greasy or waxy feel, green-black mottling, and possible magnetism from magnetite; it may scratch readily with a steel nail. Confirmatory identification requires hardness, streak, magnetism, and thin-section or XRD testing.
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