Basalt is a type of igneous rock that forms when molten LAVA cools and solidifies. It is usually black or dark gray in color and is composed of minerals such as plagioclase, pyroxene, and olivine. The term 'basalt' is derived from the Latin word for 'very hard stone'. The crossword solutions for the term 'basalt' are 'LAVA' (4 letters) and 'lavas' (5 letters). LAVA is molten rock that is expelled from a volcano during an eruption and can flow over the surface of the Earth. Lavas are the plural form of LAVA, referring to multiple flows of molten rock.