“Basalt is an effusive rock of volcan origin, it has a dark or black colour and has a relatively low (from 45 to 52%) silica content (SiO2). Basalt is manily composed by lime plagioclase and pyroxenes; some basalts can also have high content of olivine. Basalt can have different shapes as microcrystalline porphyry or glass.
It comes from magma, quickly solidified with air or water and it is the main rock which make up the superior part of oceanic crust. Basaltic magmas form thanks to fusion from decompression of earth mantle.”