Calcite is a prismatic negative uniaxial crystal with extremely high birefringence and wide transmission range (200 to 2300 nm). Although soft (Mohs hardness 3) and hygroscopic, it is the preferred material for visible-near-infrared polarizing optical components. It can be used to fabricate Glan-Taylor and Glan-Thompson polarizers and beam splitters with extinction ratio higher than 10⁶:1.