igneous
Coarse-grained mafic igneous rock, likely gabbro
Gabbro; chiefly calcium-rich plagioclase feldspar and pyroxene, with possible olivine and amphibole
AI-generated identification · may be incorrectDark greenish-gray, massive, granular texture with visible interlocking crystals; typically Mohs 6–7, dull to weakly vitreous luster, no obvious cleavage as a whole, and specific gravity about 2.8–3.1. The image suggests weathered or altered gabbro, though exact identification requires a fresh surface or testing.
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Physical properties
Dark greenish-gray, massive, granular texture with visible interlocking crystals; typically Mohs 6–7, dull to weakly vitreous luster, no obvious cleavage as a whole, and specific gravity about 2.8–3.1. The image suggests weathered or altered gabbro, though exact identification requires a fresh surface or testing.
Formation & geological history
Forms when basaltic magma cools slowly deep within oceanic or continental crust, producing coarse crystals; commonly Precambrian to Phanerozoic, depending on the intrusion. Green coloration may reflect chlorite, epidote, or serpentinization during later alteration.
Uses & applications
Used as crushed aggregate, road stone, dimension stone, and occasionally decorative building material; generally not a jewelry stone.
Geological facts
Gabbro is the intrusive equivalent of basalt and is a major component of oceanic crust. Some varieties contain economically important chromium, nickel, titanium, or platinum-group minerals.
Field identification & locations
Identify by its dark color, coarse interlocking grains, high density, and lack of layering or fossils; a streak, hardness, magnetism, and fresh broken surface help distinguish it from basalt, amphibolite, and serpentinite. Common in layered mafic intrusions and exposed oceanic crust worldwide.
