Ca2Al2SiO7F2

Ca2Al2SiO7F2 is a chemical formula that would describe a calcium–aluminum silicate with fluorine substituting for oxide within a melilite-type structure. As written, the formula does not appear to balance in simple valence accounting for common oxidation states, which suggests that if such a phase exists it would be synthetic or would require additional substitutions or vacancies to maintain charge balance. Consequently, there is no widely recognized natural mineral with this exact composition.

In mineralogy, geochemical studies often treat gehlenite, Ca2Al2SiO7, as the end-member of the melilite group. Melilites are silicate minerals built from interconnected tetrahedra and octahedral units with calcium occupying interstitial cation sites. The idea of fluorine substituting for oxygen is conceptually plausible within silicate systems, but fluorinated melilite variants are not well established in natural settings and would represent unusual solid-solution behavior or synthetic phases.

If such a fluorinated phase could be realized, it would presumably form under high-temperature conditions typical of igneous or metamorphic environments, potentially in environments where fluorine is abundant. The presence of fluorine would influence lattice parameters, stability, and properties relevant to high-temperature ceramics or refractory applications. Specific physical properties would depend on the exact crystal structure and substitution pattern.

See also: gehlenite, melilite, fluorine-substituted silicates.