An Etymological Dictionary of Astronomy and Astrophysics

A dark fine-grained → igneous rock typically composed of → plagioclase with → pyroxene and → olivine and often displaying a columnar structure.

See also: From L.L. basaltes, misspelling of L. basanites “very hard stone,” from Gk. basanites, from basanos “touchstone,” from Egyptian baban “a stone used by the Egyptians as a touchstone of gold.”