One of the major uses of crystalline silica is as a raw material for glass manufacture. The first glass was probably made in Egypt more than 5,000 years ago. Today, the process has become highly refined. To ensure a very pure product, the specifications for glass are exceptionally stringent. Pure crystalline silica is used, and there are

strict limits on the amounts of other impurities. Even the grain size of the crystals is specified. In the finished glass, the silica content must be at least 98.5%.

Commercial glass in often: 75% silica, 10% lime, and 15% soda ash. The ingredients are heated in a furnace to about 1300 degrees.

Silica is the major ingredients in virtually all types of glass. The principal glass products include containers (bottles and jars), flat glass (windows, mirrors, vehicle glazing, etc.), Lighting glass (light bulbs, fluorescent, tubes, etc.), tableware (lead crystal, drinking glasses, etc.), TV tubes and screens, decorative glass, fiberglass, optical glass and vacuum flasks.

Pure silica is needed to make clear glass, Colored glass has iron or other minerals added to it.