Quartz glass, also known as fused quartz or fused silica, is composed entirely of amorphous silica (SiO). Its high degree of purity yields superior optical and thermal properties compared to all other types of glass. Laser processing of quartz glass is achieved using either a 10.6 or 9.3 micron CO₂ laser. The 1.06 micron fiber wavelength is not absorbed by this material and will pass through it uninhibited. Laser marking of quartz glass produces a smooth uniform mark with little contrast. Alternatively, dithering can be used to create a pattern of surface microfractures, resulting in a uniform mark that is frosted in appearance. Laser engraving of quartz glass produces a smooth mark with depth and a melted appearance.