igneous
Gabbro
Gabbro
Hardness: 6 on Mohs scale, Color: Dark grey to black, Luster: Vitreous to dull, Crystal Structure: Phaneritic (coarse-grained) intrusive igneous texture, Cleavage: Varies by mineral component (plagioclase and pyroxene), Specific Gravity: 2.7 to 3.3
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Physical properties
Hardness: 6 on Mohs scale, Color: Dark grey to black, Luster: Vitreous to dull, Crystal Structure: Phaneritic (coarse-grained) intrusive igneous texture, Cleavage: Varies by mineral component (plagioclase and pyroxene), Specific Gravity: 2.7 to 3.3
Formation & geological history
Formed from the slow cooling of magnesium-rich and iron-rich magma beneath the Earth's surface, resulting in a coarse-grained intrusive rock.
Uses & applications
Used as crushed stone for construction, road base, riprap, and when polished, it is sold as black granite for architectural tiles and kitchen countertops.
Geological facts
Gabbro is the chemical equivalent of basalt; while gabbro cools slowly underground to form coarse crystals, basalt cools quickly on the surface resulting in fine grains.
Field identification & locations
Identified by its dark color and coarse interlocking grains of plagioclase feldspar and pyroxene. Common in oceanic crust and layered intrusive complexes worldwide.
