Ca2Al2SiO7

Ca2Al2SiO7 is the chemical formula for a mineral belonging to the melilite group. Minerals in this group share a common structure and general formula of A2B2TO5, where A is typically a divalent cation, B is a trivalent cation, and T is a tetravalent cation, although substitutions can occur. In Ca2Al2SiO7, calcium (Ca) occupies the A site, aluminum (Al) occupies the B site, and silicon (Si) along with some aluminum can occupy the T site, often in a disordered arrangement. This specific composition can be considered a member of the gehlenite series, where the end-member gehlenite is Ca2Al2SiO7.

Ca2Al2SiO7 typically forms in high-temperature, low-pressure metamorphic environments, such as in contact metamorphosed limestones and skarns. It can also be found in some volcanic rocks and meteorites. The mineral is known for its glassy luster and is often found as euhedral to subhedral crystals, or as masses. Its color can vary, commonly appearing colorless, white, gray, or pale yellow. Due to its specific formation conditions, Ca2Al2SiO7 is not a widespread rock-forming mineral. Its presence can indicate particular geological processes and conditions.