igneous
Likely gabbro or coarse-grained basalt
Gabbro (plagioclase + clinopyroxene ± olivine, Fe-Ti oxides)
AI-generated identification · may be incorrectDark gray to black, coarse crystalline texture with metallic-to-vitreous sparkle; typically Mohs 6–7, massive, with little or no cleavage as a whole rock. The visible pale grains are likely plagioclase, while dark grains are pyroxene and possibly magnetite.
Identified More igneous →
Explore Likely gabbro or coarse-grained basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, coarse crystalline texture with metallic-to-vitreous sparkle; typically Mohs 6–7, massive, with little or no cleavage as a whole rock. The visible pale grains are likely plagioclase, while dark grains are pyroxene and possibly magnetite.
Formation & geological history
An intrusive mafic igneous rock formed by slow cooling of iron- and magnesium-rich magma deep in the crust, commonly during Precambrian to younger oceanic-crust formation. If the texture is less crystalline than it appears, it could instead be basalt, the volcanic equivalent.
Uses & applications
Used as crushed aggregate, road stone, riprap, dimension stone, and polished architectural material; generally low jewelry value unless unusually attractive or associated with crystals.
Geological facts
Gabbro is chemically equivalent to basalt but cools slowly, producing larger crystals. Strong magnetism may indicate abundant magnetite or titanomagnetite.
Field identification & locations
Identify it by its dense black color, visible interlocking crystals, high specific gravity, and possible weak magnetism; common in oceanic crust, layered intrusions, and ancient mafic terranes. The photograph alone cannot distinguish gabbro confidently from basalt, diabase, or magnetite-rich metamorphic rock.
