If you need a glossary of mining terms, here is one...
http://www.infomine.com/dictionary/
Definition: gabbro
1. A group of dark-colored, basic intrusive igneous rocks composed principally of basic plagioclase (commonly labradorite or bytownite) and clinopyroxene (augite), with or without olivine and orthopyroxene; also, any member of that group. It is the approximate intrusive equivalent of basalt. Apatite and magnetite or ilmenite are common accessory minerals.
Source: AGI
Hope this help !