The Formation of Basalt David Attenborough talks about the formation of Basalt (Bluestone) Basalt is an aphanitic (fine-grained) igneous rock with less than 20% quartz and less than 10% feldspathoid by volume, and where at least 65% of the feldspar is in the form of plagioclase. Basalt features a glassy matrix interspersed with minerals. The … Continue reading The Formation Of Basalt