Hard, dark igneous rock, composed of 45 to 54 percent silica (SiO2) and often rich in iron and magnesium. Basalt is the most common type of rock in the crusts of many terrestrial worlds (especially Selenian, Arean, Venusian, and Gaian worlds.
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Development Notes
Text by M. Alan Kazlev
Initially published on 08 October 2001.