metamorphic
Serpentinite (serpentinized ultramafic rock), possibly with chromite
Serpentine-group minerals, chiefly lizardite and chrysotile; commonly derived from peridotite or pyroxenite, with possible chromite and magnetite
AI-generated identification · may be incorrectTypically green to black, mottled, waxy to greasy luster; Mohs hardness 2.5–5.5, nonfoliated to weakly schistose, with poor cleavage. The specimen shows green-yellow alteration, dark opaque grains, and rusty iron-oxide staining.
Identified More metamorphic →
Explore Serpentinite (serpentinized ultramafic rock), possibly with chromite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Typically green to black, mottled, waxy to greasy luster; Mohs hardness 2.5–5.5, nonfoliated to weakly schistose, with poor cleavage. The specimen shows green-yellow alteration, dark opaque grains, and rusty iron-oxide staining.
Formation & geological history
Forms when mantle-derived peridotite hydrates during low-temperature metamorphism, commonly along oceanic crust, faults, and subduction zones; ages vary widely from Precambrian to recent tectonic exposure.
Uses & applications
Used as decorative stone, carving material, aggregate, and historically as a source of asbestos-bearing serpentine; attractive pieces are collected, though fibrous material should not be cut or powdered.
Geological facts
Serpentinite often contains magnetite and may be weakly magnetic; associated chromite can produce black, granular patches. It is the characteristic rock of many ophiolite belts.
Field identification & locations
Identify by its green-black mottled color, waxy surface, low hardness, and association with dark ultramafic cobbles; a streak, magnet, and acid test can help, but avoid disturbing possible asbestos fibers. Common in California, the Appalachians, New Zealand, and ophiolite zones worldwide.
More like this
