Fused quartz or
fused silica is
glass consisting of
silica in
amorphous (non-
crystalline) form. It differs from traditional
glasses in containing no other ingredients, which are typically added to glass to lower the melt temperature. Fused silica, therefore, has high working and melting temperatures. The optical and thermal properties of fused quartz are superior to those of other types of glass due to its purity. For these reasons, it finds use in situations such as
semiconductor fabrication and laboratory equipment. It has better
ultraviolet transmission than most other glasses, and so is used to make
lenses and other optics for the ultraviolet spectrum. Its low
coefficient of thermal expansion also makes it a useful material for precision mirror substrates.