Basalt is an igneous rock that contains more than 45 and less than 52% of SiO 2 and less than five percent of total alkalies (K 2 O + Na 2 O) 3. Neighboring rock types like basaltic andesite, basanite, picrite (picrobasalt), trachybasalt and even more distant rocks like phonotephrite or andesite may have very similar look and can be easily mistaken for basalt in many cases. .