High Quality Content by WIKIPEDIA articles! Fused quartz and fused silica are types of glass containing primarily silica in amorphous (non-crystalline) form. They are manufactured using several different processes. Note that glasses formed by the traditional 'melt-quench' methods, are often referred to as 'vitreous', as in 'vitreous silica'. The term 'vitreous' is synonymous with 'glass', when used in the melt-quench context. Fused quartz is manufactured by melting naturally occurring quartz crystals of high purity at approximately 2000°C, using either an electrically heated furnace (electrically fused) or a gas/oxygen-fuelled furnace. Fused quartz is normally transparent.