Optically, crystalline quartz is used extensively as a wave retardation medium, using the birefringent properties for use in quarter-wave plates and in polarizers. Quartz is mined naturally, but more commonly produced synthetically in large long faceted crystals. Quartz is positive birefringent. Be careful not to confuse terminology in this material, as "fused quartz" is often used to denote the glassy non-crystalline form better known as silica.

Optical Quality Cultured Crystalline Quartz is available in three grades defined by optical absorption at two wavelength: 190 nm and 2800 nm (a - index of absorption, 1/cm).