diopsidehedenbergite

Diopsidehedenbergite, often written diopside–hedenbergite, is not a separate mineral species but a continuous solid-solution series within the clinopyroxene group. The series describes compositions in which calcium and the SiO4 tetrahedra form a fixed framework while the Mg2+ and Fe2+ content varies through substitution, producing intermediate members between diopside and hedenbergite.

The end-members are diopside, CaMgSi2O6, and hedenbergite, CaFeSi2O6. The general formula for the series is Ca(Mg,Fe)Si2O6, with Fe2+ substituting for Mg2+ in the pyroxene structure. Minor substitutions, such as aluminum for silicon and trace alkalis, can occur in natural samples and modulate crystal chemistry and color.

Occurrence and textures: Diopside-hedenbergite is common in a wide range of igneous and metamorphic rocks, particularly in mafic to ultramafic compositions and in contact metamorphic settings like skarns. It forms as prismatic, elongated crystals or as granular to granoblastic masses. The color varies from green in more Mg-rich compositions to greenish-brown in Fe-rich varieties.

Significance: The diopside-hedenbergite series is a key component of the clinopyroxene group and is used in petrographic analysis and geothermobarometry. The Fe/Mg ratio in these pyroxenes provides information about crystallization temperature, pressure, and oxidation state during rock formation or metamorphism. In some classifications, this series is grouped with the augite family of pyroxenes.