Quartz facts for kids
Quartz crystal cluster from Tibet
|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|
|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
|Twinning||Common Dauphine law, Brazil law and Japan law|
|Mohs scale hardness||7 – lower in impure varieties (defining mineral)|
|Luster||Vitreous – waxy to dull when massive|
|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)|
|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 is the second most common mineral in Earth's continental crust. Its crystal structure is a framework of SiO4 silicon–oxygen 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.
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.
Images for kids
Fatimid ewer in carved rock crystal (clear quartz) with gold lid, c. 1000.
Quartz Facts for Kids. Kiddle Encyclopedia.