Calcite is well known material for polarization optics. Due to structural anisotropy it has two refractive indices. So it divides an entering beam of monochromatic light into two beam having opposite polarization. This phenomenon is used to build polarization components. As the difference in the two refractive indices is very large calcite has become the most popular crystal in polarization applications.

Calcite is a negative uniaxial crystal that has high birefringence, wide spectral transmission and availability in reasonably-sized rhombs. Although it is a soft crystal and is easily scratched, it is an ideal material used as visiable and IR polarizers, such as Glan Taylor, Glan Thompson and Glan laser.