GABBRO

Appearance and Texture

• Color: Usually dark gray to black, but can be greenish or light gray depending on mineral mix

• Texture: Phaneritic (coarse-grained) – individual crystals can be seen with the naked eye

• Hardness: 6–7 on Mohs scale

Formation

Gabbro forms when mafic magma cools slowly deep underground in large plutons or intrusions. This slow cooling allows large crystals to grow. It is chemically similar to basalt, but while basalt erupts at the surface, gabbro crystallizes beneath the surface.

Where It’s Commonly Found?

Gabbro is commonly found in:

• Oceanic crust – especially at mid-ocean ridges

• Continental crust – in large igneous intrusions

• Famous locations:

• Skaergaard Intrusion (Greenland)

• Bushveld Complex (South Africa)

Uses and Importance

Thanks to its toughness and availability, gabbro is used for:

• Construction aggregate – crushed for roads, foundations, and rail beds

• Dimension stone – polished and used for countertops, tiles, and facades

• Mining – source of metals like nickel, copper, chromium, and platinum

Fun Fact / Trivia

When polished, gabbro is often sold as “black granite” in construction and interior design, even though it's a different type of rock. Granite is felsic and lighter in color, while gabbro is mafic and darker.