Dolerite

Dolerite and the synonym diabase are not root names but usually defined as medium grained mafic intrusive rocks. It can include microgabbro, basalt, andesite, microdiorite and other rock types. i. In the United States, a syn. of diabase Ref: AGI ii. In British and Australian usage: A medium grained mafic intrusive rock whose main components are calcic plagioclase and clinopyroxene and which is characterized by ophitic to subophitic texture; usually found in sills and dykes. The preferred term for what is called diabase in the United States. Of similar mineralogy to basalt and gabbro, and intermediate in grain size between them. Compare with: diorite, trap.