Quartz belongs to the trigonal crystal system at room temperature, and to the hexagonal crystal system above 573 ☌ (846 K 1,063 ☏). Today, the term rock crystal is sometimes used as an alternative name for transparent coarsely crystalline quartz. The Ancient Greeks referred to quartz as κρύσταλλος ( krustallos) derived from the Ancient Greek κρύος ( kruos) meaning "icy cold", because some philosophers (including Theophrastus) understood that the mineral to be a form of supercooled ice. The word "quartz" is derived from the German word Quarz, which had the same form in the first half of the 14th century in Middle High German and in East Central German and which came from the Polish dialect term kwardy code: pol promoted to code: pl, which corresponds to the Czech term tvrdý ("hard"). Quartz is the mineral defining the value of 7 on the Mohs scale of hardness, a qualitative scratch method for determining the hardness of a material to abrasion. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia. There are many different varieties of quartz, several of which are classified as gemstones. Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold. The transformation from α-quartz to β-quartz takes place abruptly at 573 ☌ (846 K 1,063 ☏). Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral.
Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. The atoms are linked in a continuous framework of SiO 4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO 2. Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). Lattice: hexagonal, Piezoelectric, may be triboluminescent, chiral (hence optically active if not racemic) Insoluble at STP 1 ppm mass at 400 ☌ and 500 lb/in 2 to 2600 ppm mass at 500 ☌ and 1500 lb/in 2 181) Ĭolorless through various colors (pink, orange, purple, dark brown)Ħ-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massiveĬommon Dauphine law, Brazil law and Japan lawħ – lower in impure varieties (defining mineral)Ģ.65 variable 2.59–2.63 in impure varietiesġ670 ☌ (β tridymite) 1713 ☌ (β cristobalite)
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