Basalt

Introduction: Basalt has the same mineral composition as gabbro and dolerite even though it is an extrusive rock. It is a fine-grained rock because of the quick-fire cooling and chilling process it goes through when formed. Its dense microscopic crystals often form colonies and is the most common form of igneous rock.

Distribution: The Waterberg area, Etendeka lavas in north-west Namibia and in the Goboboseb Mountains at Tafelkop, west of Brandberg.

Composition: Basalt contains vesicles (bubbles and hollows) filled with secondary minerals such as calcite, agates and quartz.

Colouration: A dark greenish to grey mafic rock.

Uses: Excavated for minerals.