An aluminium silicate found in both igneous and metamorphic rocks. It is a very large group of minerals which can be broken down into two smaller subgroups -- clinopyroxene and orthopyroxene. This distinction refers to their optical properties when viewed in thin section under the microscope. They are very prolific and consist of several varieties which are part of solid solution series.
Pyroxenes and amphiboles are related minerals -- amphiboles are the hydrated forms of pyroxene.