Gabbro is a widespread rock,
particularly in the oceanic crust.
It is an intrusive
with medium to large grain size.
It is a dark rock,
mainly made from dark minerals such as pyroxene,
olivine and biotite.
contains small amounts of lighter minerals such as quartz and sanidine.
By AlishaV via Flickr.com
It is similar to diorite,
but its plagioclase is calcium-rich instead of rich in sodium which is
the case with diorite.
If the magma with the same composition would form an extrusive
it would be basalt.
Mike Beauregard via Flickr.com
are a few variations
such as layered, olivine, and coarse, aka leucogabbro, while basalt is quite uniform
comes to mineral composition.
It is a rock that can contain ore minerals, and is sometimes mined for
iron, titanium, platinum, chromium and nickel.