consists of SiO2. Its density is approximately 2.2 g/cm3, refractive index 1.460. Worth mentioning is its low coefficient of expansion. Its high thermal shock resistance is attributable to this. The high-temperature softening point of quartz glass enables the production of devices that withstand temperatures of up to 1400 °C. Further useful characteristics of quartz glass are a high internal transmittance between approx. 200 to 4000 nm, good resistance to chemicals, and low electric conductivity. A disadvantage of quartz glass is its very difficult machinability.