Aegirinehedenbergite

Aegirinehedenbergite is a mineral belonging to the clinopyroxene group. It is an end-member of the aegirine-hedenbergite solid solution series, which is a part of the larger alkali pyroxene series. The chemical formula for aegirinehedenbergite is ideally CaFe³⁺Si₂O₆. It is characterized by its dark color, typically black or dark green, and its monoclinic crystal system. The mineral forms prismatic crystals, often elongated and striated.

Aegirinehedenbergite is found in a variety of igneous rocks, particularly those that are alkaline in composition. It commonly occurs in alkaline basalts, syenites, and carbonatites. It can also be found in some metamorphic rocks, such as granulites. Its formation is often associated with environments rich in iron and calcium. Examples of localities where aegirinehedenbergite has been described include Greenland, Norway, and various volcanic regions.

The optical properties of aegirinehedenbergite include a relatively high refractive index and a distinct pleochroism, meaning it appears to have different colors when viewed from different angles. Its hardness is typically around 5.5 to 6 on the Mohs scale. While not a common ore mineral, its presence can be indicative of specific geological conditions and magmatic processes.