ETYM Latin basaltes (an African word), a dark and hard species of marble found in Ethiopia: cf. French basalte.
The commonest type of solidified lava; a dense dark gray fine-grained igneous rock composed chiefly of calcium-rich plagioclase feldspar and pyroxene.
Greenish-black igneous rock, often forming columns.
Commonest volcanic igneous rock, and the principal rock type on the ocean floor; it is basic, that is, it contains relatively little silica: about 50%. It is usually dark gray but can also be green, brown, or black.
The groundmass may be glassy or finely crystalline, sometimes with large crystals embedded. Basaltic lava tends to be runny and flows for great distances before solidifying. Successive eruptions of basalt have formed the great plateaus of Colorado and the Indian Deccan. In some places, such as Fingal's Cave in the Inner Hebrides of Scotland and the Giant's Causeway in Antrim, Northern Ireland, shrinkage during the solidification of the molten lava caused the formation of hexagonal columns.

ETYM Cf. French basaltique.
Of or relating to or containing basalt.