Gabbro
“The deep ocean's dark heart”
Igneous
Gabbro is a dark, coarse-grained intrusive igneous rock that forms deep beneath oceanic spreading ridges. It's essentially the slow-cooled, plutonic equivalent of basalt and makes up a significant portion of the lower oceanic crust.
Composition
plagioclase feldspar, pyroxene (augite), olivine, hornblende
Where Found
Bushveld Complex (South Africa), Oman Ophiolite, Stillwater (Montana, USA), Scotland
Mohs Hardness
6-7
Fun Fact
Commercially, much of the polished stone sold as 'black granite' for countertops is actually gabbro.
Test Your Knowledge
At what type of tectonic boundary does the majority of Earth's gabbro form?
Related Specimens
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