Basalt is a basic igneous effusive rock, dark or black. It is rich in minerals and fine-grained due to rapid cooling of lava at the surface of a planet, in contact with air or water. Basalt is principally composed of plagioclase, pyroxene and frequently olivine. Basaltic lava has a low viscosity and flow easily covering large areas such as the Deccan Plateau in India that extend to 600,000 km2, twice the area of Italy; sometimes it solidifies in particular hexagonal columns.

It’s the most abundant effusive rock of the earth’s crust and ocean floors are predominantly made up of basalt. It’s important to note that the content of silica SiO2 is around about 50%, lower than 70% of glass and common granitic rocks. Moreover, the alkali metals content is higher in basalt as a typical basic rock.

Basalt, as an effusive rock, has a thermoplastic behaviour and melts at a temperature of about 1450°C (2550°F); it has low thermal conductivity, assumed to be 0.035 W/mK, comparable to that of glass fiber or common materials used to production of filaments for structural use.