Glass

Glass is a uniform material of arguable phase, usually produced when the viscous molten material cools very rapidly to below its glass transition temperature, without sufficient time for a regular crystal lattice to form. The most familiar form of glass is the Silica-based material used for household objects such as light bulbs and windows.

Glass is a biologically inactive material that can be formed into smooth and impervious surfaces. Glass is brittle and will break into sharp shards. These properties can be modified or changed with the addition of other compounds or heat treatment.

Common glass contains about 70-72 weight % of silicon dioxide (SiO₂). The major raw material is sand (or "quartz sand") that contains almost 100% of crystalline silica in the form of quartz. Although it is an almost pure quartz, it may still contain a small amount (< 1%) of iron oxides that would color the glass, so this sand is usually enriched in the factory to reduce the iron oxide amount to < 0.05%. Large natural single crystals of quartz are purer silicon dioxide, and upon crushing are used for high quality specialty glasses. Synthetic amorphous silica (practically 100% pure) is the raw material for the most expensive specialty glasses.

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