Distinctive features:  
Texture, colour, denseness and often contorted by flow on eruption or cindery.

Colour: 
Dark greenish-grey to black.

Texture and granularity: 
Aphanitic with crystals that are too small to identify with the naked eye unless they occur as phenocryusts (e.g. augite and/or olivine). Fine-grained equivalent of gabbro.

Composition: 
Pyroxene and plagioclase, with pyroxene appearing in freater amounts than plagioclase or equal amounts. Olivine is also often present, as well as grains of iron ore (magnetite and/or ilmenite) and bronze-coloured biottie. It may contain olivine or pyroxzene nodules brought up from depth.

Field associations: 
As lava, flows, sills and dykes associated with volcanoes.

Varieties:
Olivine basalt, which is basalt plus olivin phenocrysts, and quartz basalt, which is vasalt plus scarce quantities of quartz.

 

Worldwide, but particularly in Canada (Lake Superior has vast copper deposits), Greenland, India (Deccan traps), Iceland, Scotland, USA (Montana, western states).

 

Roadstone aggregate, source of iron ore, sapphires and native copper.