Ortopyroxenes

Ortopyroxenes are a group of silicate minerals belonging to the pyroxene family. They are characterized by their orthorhombic crystal structure. Ortopyroxenes are solid solutions of magnesium and iron, with their chemical formula generally represented as (Mg,Fe)SiO3. The end-members of the ortopyroxene series are enstatite (Mg2Si2O6) and ferrosilite (Fe2Si2O6). In natural samples, intermediate compositions containing both magnesium and iron are common, often referred to by specific names such as bronzite and hypersthene depending on their iron content.

These minerals typically form in igneous rocks, particularly those that are relatively magnesium-rich, such as peridotites and gabbros. They are also found in some metamorphic rocks that have undergone high-temperature metamorphism. Ortopyroxenes are generally hard and brittle, with a Mohs hardness typically ranging from 5.5 to 6.5. They exhibit cleavage along two directions that are nearly perpendicular to each other. Their color can vary from colorless or pale green in magnesium-rich varieties to dark brown or black in iron-rich compositions. Ortopyroxenes are important components in understanding the petrogenesis and geological history of many rock formations.