Dolorite

Introduction: The intrusive equivalent of gabbro as it has the same mineral and chemical composition. Dolerite is found in either sills, sheet-like compositions that intrude horizontally and dykes, which are vertical or inclined features.

Distribution: Dolerite is harder than surrounding sedimentary rock and can resist weathering. Flat tops can be formed on hills because of this durability. The dolerite boulder-strewn slopes are a common feature in some areas of Namibia.

Composition: Fine-grained. Dolerite can store huge amounts of underground water.

Colouration: A very hard, dark grey rock.

Uses: Dolerite is quarried and used in road construction, often as a crushed aggregate found in tarred roads.