igneous
Gabbro
Gabbro
Hardness: 6 on the Mohs scale. Color: Dark gray to black, often with a speckled appearance due to white plagioclase. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained), consisting mainly of calcium-rich plagioclase feldspar and clinopyroxene. Specific gravity: 2.7 to 3.3.
- Hardness
- 6 on the Mohs scale
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6 on the Mohs scale. Color: Dark gray to black, often with a speckled appearance due to white plagioclase. Luster: Vitreous to dull. Crystal structure: Phaneritic (coarse-grained), consisting mainly of calcium-rich plagioclase feldspar and clinopyroxene. 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, creating a coarse-grained intrusive igneous rock. It is the intrusive equivalent of basalt.
Uses & applications
Used in construction, as crushed stone for roadbeds, as dimension stone (often sold commercially as 'black granite'), and occasionally for monuments and countertops.
Geological facts
Gabbro makes up a large portion of the Earth's oceanic crust. Because of its dark color and durability, it is heavily quarried and polished for architectural and decorative purposes under the trade name 'black granite'.
Field identification & locations
Identify in the field by its dark color, coarse crystalline texture, and lack of quartz. Commonly found in oceanic crust, layered intrusions, and ophiolite complexes worldwide.
