Pure fluorite is colorless and transparent under visible and ultraviolet light, but impurities often make it a colored mineral with ornamental and gemstone uses. Industrially, fluorspar is used as a flux in smelting and in the production of certain glasses and enamels. The purest grade of fluorspar is the source of fluoride for the manufacture of hydrofluoric acid, an intermediate source for most fluorine-containing fine chemicals. Optically clear fluorite lenses have low dispersion, so lenses made from fluorite have less chromatic aberration, making them valuable in microscopes and telescopes. Fluorite optics can also be used in the far ultraviolet and mid-infrared ranges where traditional glass is too opaque to be used.