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Fused quartz is produced by fusing (melting) high-purity silica sand, which consists of quartz crystals. There are four basic types of commercial silica glass: Type I is produced by induction melting natural quartz in a vacuum or an inert atmosphere. Type II is produced by fusing quartz crystal powder in a high-temperature flame.
Melting point: 1670 °C (β tridymite); ... Quartz is a hard, ... Lechatelierite is an amorphous silica glass SiO 2 which is formed by lightning strikes in quartz sand.
Soda–lime glass (for containers) [2] Borosilicate (low expansion, similar to Pyrex, Duran) Glass wool (for thermal insulation) Special optical glass (similar to Lead crystal) Fused silica Germania glass Germanium selenide glass Chemical composition, wt% 74 SiO 2, 13 Na 2 O, 10.5 CaO, 1.3 Al 2 O 3, 0.3 K 2 O, 0.2 SO 3, 0.2 MgO, 0.01 TiO 2, 0. ...
Vitrified sand is a type of natural glass, contrasted with manufactured glass in which soda ash or potash are added to lower the melting point. Pure quartz melts at 1,650 °C (3,002 °F). There are several natural processes that produce more or less melted sand and one man-made form: Fulgurite is sand fused by a lightning bolt hitting sand.
As other minerals are melted with silica, the principle of freezing point depression lowers the melting point of the mixture and increases fluidity. The glass transition temperature of pure SiO 2 is about 1475 K. [ 35 ] When molten silicon dioxide SiO 2 is rapidly cooled, it does not crystallize, but solidifies as a glass. [ 36 ]
Fused quartz is used for high-temperature applications such as furnace tubes, lighting tubes, melting crucibles, etc. [74] However, its high melting temperature (1723 °C) and viscosity make it difficult to work with. Therefore, normally, other substances (fluxes) are added to lower the melting temperature and simplify glass processing. [75]
Melting point: 1,713 °C (3,115 ... Both quartz and cristobalite are polymorphs with all the members of the quartz group, ... a volcanic glass. References
The Gmelin rare earths handbook lists 1522 °C and 1550 °C as two melting points given in the literature, the most recent reference [Handbook on the chemistry and physics of rare earths, vol.12 (1989)] is given with 1529 °C.