Ca2MgSi2O7

Ca2MgSi2O7, commonly referred to as akermanite, is a calcium magnesium silicate mineral and the magnesium-rich end-member of the melilite group. The melilite minerals form a solid solution between gehlenite (Ca2Al2SiO7) and akermanite, with aluminum able to substitute for magnesium in the crystal structure. Akermanite represents the composition at the Mg-rich end of that series.

Akermanite occurs in high-temperature environments such as certain igneous rocks including nephelinite and other alkali-rich rocks, as well as in zones affected by contact metamorphism near intrusive bodies. It is typically found in granular to igneous textures, and can be associated with other melilites along with minerals such as diopside and garnet in suitable rock assemblages.

In terms of physical properties, akermanite is usually colorless to pale yellow-brown, with a vitreous luster and a Mohs hardness around 5.5 to 6. It crystallizes in the tetragonal system and generally exhibits a specific gravity of about 3.3 to 3.4. The mineral can appear as euhedral to subhedral crystals or as part of a granular aggregate, depending on the rock type and cooling history.

Geologically, akermanite serves as a marker for high-temperature, calcium- and magnesium-rich silicate assemblages. It is mainly of interest to mineralogists and petrologists, rather than as a bulk ore mineral. Its study helps illuminate melilite-bearing parageneses in igneous and contact-metamorphic rocks.

See also: Melilite group, Gehlenite.