Quartz facts for kids

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Quartz
Quartz, Tibet.jpg
Quartz crystal cluster from Tibet
General
Category oxide mineral
Formula
(repeating unit)
SiO2
Strunz classification 4.DA.05 (Oxides)
Dana classification 75.01.03.01 (tectosilicates)
Unit cell a = 4.9133 Å, c = 5.4053 Å; Z=3
Identification
Color Colorless through various colors to black
Crystal habit 6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive
Crystal system α-quartz: trigonal
β-quartz: hexagonal
Twinning Common Dauphine law, Brazil law and Japan law
Cleavage {0110} Indistinct
Fracture Conchoidal
Tenacity Brittle
Mohs scale hardness 7 – lower in impure varieties (defining mineral)
Luster Vitreous – waxy to dull when massive
Streak White
Diaphaneity Transparent to nearly opaque
Specific gravity 2.65; variable 2.59–2.63 in impure varieties
Optical properties Uniaxial (+)
Refractive index nω = 1.543–1.545
nε = 1.552–1.554
Birefringence +0.009 (B-G interval)
Pleochroism None
Melting point 1670 °C (β tridymite) 1713 °C (β cristobalite)
Solubility Insoluble at STP; 1 ppmmass at 400 °C and 500 lb/in2 to 2600 ppmmass at 500 °C and 1500 lb/in2
Other characteristics lattice: hexagonal, Piezoelectric, may be triboluminescent, chiral (hence optically active if not racemic)
Quartz oisan
Quartz crystal
QuartzUSGOV
Quartz

Quartz is the second most common mineral in Earth's continental crust. Its crystal structure is a framework of SiO4 siliconoxygen tetrahedra. Each shares an oxygen atom oxygen with another tetrahedron, so the overall chemical formula is SiO2 or silica.

There are many different varieties of quartz, some of which are semi-precious gemstones. Varieties of quartz have been used for a long time in the making of jewelry and hardstone carving. Agate, amethyst, rose quartz are all forms of quartz.

Quartz is a component used to make quartz clocks. Sand often has a lot of small quartz bits. This mineral contains silica. Quartz has a mineral hardness of 8. (mohs scale).

The word "quartz" comes from the German word "quarz".

'Fused quartz' is glass made of silica in non-crystalline form. It does not contain other ingredients. These are usually added to glass to lower the melt temperature. Fused silica has high working and melting temperatures. The properties of fused quartz are superior to those of other types of glass due to its purity. The glass is used in a number of high-tech products.

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Quartz Facts for Kids. Kiddle Encyclopedia.