Gabbro

Main Elements:

Si, Al, Fe, Mg, Ca, Na, O

Chemical Composition:

SiO₂ 45-52%, Al₂O₃ 14-18%, FeO 5-14%, MgO 5-12%, CaO 8-12%, Na₂O 2-5%

Density:

2.9-3.1 g/cm³

Compressive Strength:

150-300 MPa

Melting Point:

1000-1200°C

Formation:

Forms from slowly cooled mafic magma deep beneath the Earth's surface. Makes up much of the oceanic crust.

Composition:

Composed mainly of plagioclase feldspar, pyroxene, and olivine. The intrusive equivalent of basalt.

Types:

• Norite
• Troctolite
• Anorthosite Gabbro

Etymology:

Named after Gabbro, a town in Italy, though the rock was originally called "gabbro" by Italian geologists.

Uses:

• Construction
• Decorative stone
• Countertops
• Monuments

Distribution:

Found worldwide, especially in oceanic crust and layered intrusions

Historical Use:

Used in construction and monuments. The famous "Black Granite" used in buildings is often gabbro.

Symbolism:

Represents strength, density, and Earth's foundation

What is the difference between gabbro and basalt?

Gabbro is the intrusive (slow-cooled) equivalent of basalt. Gabbro has larger crystals due to slower cooling, while basalt has fine-grained texture from rapid cooling.

Where is gabbro found?

Gabbro forms much of the oceanic crust and is also found in continental intrusions and layered igneous complexes.