metamorphic
Serpentinized ultramafic rock with chromite
Serpentinite; chiefly serpentine-group minerals, Mg-rich silicates, with probable chromite and minor magnetite
AI-generated identification · may be incorrectTypically Mohs 2.5–4, waxy to greasy luster, green, gray, or black mottling, and a massive texture with no obvious cleavage. The specimen appears pale serpentine-rich with dark green-black, granular chromite/magnetite zones; exact identification requires testing.
Identified More metamorphic →
Explore Serpentinized ultramafic rock with chromite in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Typically Mohs 2.5–4, waxy to greasy luster, green, gray, or black mottling, and a massive texture with no obvious cleavage. The specimen appears pale serpentine-rich with dark green-black, granular chromite/magnetite zones; exact identification requires testing.
Formation & geological history
Forms when mantle peridotite is hydrated and metamorphosed by circulating water, commonly along oceanic crust and tectonic fault zones. Serpentinization is mostly Mesozoic to Recent depending on the host terrane.
Uses & applications
Used as decorative stone, carvings, countertops, and historically for asbestos-bearing serpentinite products; chromite is an important chromium ore. Collecting value is generally modest unless unusually attractive or locality-specific.
Geological facts
Serpentinite can feel unusually smooth or greasy and may be relatively low density. Some serpentinites contain chrysotile asbestos, so avoid cutting, drilling, or generating dust.
Field identification & locations
Look for a mottled green-black color, waxy surface, low hardness, and possible attraction to a magnet from magnetite; chromite is usually dark and weakly magnetic or nonmagnetic. Common in California, the Appalachians, the Alps, New Zealand, and other ophiolite belts.
More like this
