Pyroxenes are a group of important rock-forming minerals found in many igneous and metamorphic rocks. They are typically characterized by their dark color, high density, and two distinct cleavage angles of about 90 degrees. Pyroxenes are silicate minerals, meaning they contain silicon and oxygen, and they often include elements like magnesium, iron, and calcium. These minerals play a crucial role in understanding the Earth's geology and the formation of volcanic rocks. Common types of pyroxenes include augite and diopside, which can be identified by their unique crystal structures and chemical compositions. Their presence helps geologists interpret the conditions under which rocks were formed.