Although crystal quartz is made of SiO2, it is different from fused silica, it is a positive uniaxial birefringent crystal. It features its very small birefringent refractive index difference, so it is always used in waveplates and other polarization control application.
Transmission Range: 200 nm~2500 nm
Thermal Expansion Coefficient: ||a=13.2 x 10-6/K, ||c=7.1 x 10-6/K
Density: 2.65 g/cm3