A dark coloured, medium grained igneous rock.
Dark-gray, orange- to brown- to gray-weathering, medium- to fine-grained intrusive igneous rock, commonly fractured into well-developed columnar joints, compositionally similar to basalt; occurs as dikes and sills in both the lowlands and uplands; locally known as traprock. Dolerite is quarried for use as crushed stone.
Medium grained igneous rock with composition similar to basalt. Usually found in dykes or sills.
A medium grained igneous rock which is emplaced within the earth's crust in the form of dykes and sills, and has the same mineralogy as basalt.
(geology): An igneous rock with fine grains, consisting of equal quantities of the minerals feldspar and pyroxene. During the Jurassic Period, enormous quantities of dolerite were injected into the Karoo Sequence deposits as vertical dykes and horizontal sills. Because of its resistance to erosion, dolerite dykes and sills have shaped many landscapes, especially the eastern Karoo.
a dark igneous rock typically occurring in dykes and sills.
Hard black rocks found as small nodules; used for mining.
intrusive dyke rock made up mostly of feldspar and pyroxene
fine-grained hypabyssal eruptive rock, having a basaltic composition.
A mafic intrusive rock, similar in composition to, but finer-grained than, gabbro
A dark igneous rock of medium grain size which is relatively rich in iron and magnesium minerals.
