igneous
Gabbro
Gabbro
Hardness: 6-7 on the Mohs scale. Color: Dark green, dark gray, or black with lighter flecks. Luster: Dull to sub-vitreous. Crystal structure: Phanertic (coarse-grained) with visible plagioclase feldspar and pyroxene crystals. Specific gravity: 2.7-3.3.
- Hardness
- 6-7 on the Mohs scale
- Color
- Dark green, dark gray, or black with lighter flecks
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on the Mohs scale. Color: Dark green, dark gray, or black with lighter flecks. Luster: Dull to sub-vitreous. Crystal structure: Phanertic (coarse-grained) with visible plagioclase feldspar and pyroxene crystals. Specific gravity: 2.7-3.3.
Formation & geological history
Formed from the slow cooling of magnesium- and iron-rich magma beneath the Earth's surface, creating an intrusive igneous rock equivalent to basalt.
Uses & applications
Used in construction, as crushed stone for road bases, as dimension stone, and polished for kitchen countertops and monuments under the trade name 'black granite'.
Geological facts
Gabbro makes up a large portion of the Earth's oceanic crust and is commonly found in layered intrusions worldwide.
Field identification & locations
Identify by its dark, speckled appearance containing predominantly plagioclase feldspar and clinopyroxene. Found globally in ancient shield areas and ophiolite complexes.
