Pyroxenes are a group of important rock-forming minerals found in many igneous and metamorphic rocks. They are typically characterized by their two distinctive cleavage angles of about 90 degrees and are composed mainly of silicate minerals containing iron, magnesium, and calcium. Common types of pyroxenes include augite and diopside. These minerals play a crucial role in understanding the composition and evolution of the Earth's crust and mantle. Pyroxenes are also significant in petrology, the study of rocks, as they help geologists identify the conditions under which rocks formed.