CaAl2Si2O8NaAlSi3O8

CaAl2Si2O8NaAlSi3O8 is a chemical formula representing a mineral that is a member of the feldspar group. Specifically, it describes a solid solution between anorthite (CaAl2Si2O8) and albite (NaAlSi3O8). This compositional range falls within the plagioclase feldspar series. Plagioclase feldspars are tectosilicate minerals, meaning their atomic structure is built upon a framework of interconnected silica and alumina tetrahedra. The presence of calcium and sodium ions in the structure balances the charges of the aluminum and silicon within the framework.

Minerals with this general composition can be found in a variety of igneous and metamorphic rocks. They are particularly common in felsic and intermediate igneous rocks such as granite, diorite, andesite, and gabbro. In metamorphic environments, they can form during regional and contact metamorphism of pre-existing rocks. The specific proportions of anorthite and albite within the solid solution determine the mineral's precise physical properties, including its hardness, specific gravity, and refractive index. The nomenclature for plagioclase feldspars is often based on the percentage of the albite end-member, with CaAl2Si2O8NaAlSi3O8 encompassing a broad range of compositions.