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Brief Description: Quartz has several names. In the ancient times (Theophrastus) and until the mid-17th century, the clear colourless quartz was called crystal = ice, from the Greek words kryos (cold) and stello (send). It has the chemical formula SiO2 and it belongs to the category Tectosilicates (SiO2 group). Its lustre is vitreous in microcrystalline varieties and dull or sebaceous in cryptocrystalline varieties. It is white or colourless. Often, it contains small inclusions that give it colour, like milky, violet, brown, red, yellow, green, black etc. Its specific weight is almost 2.65, its hardness 7 and its fusibility 7 as well. It has prismatic form or rhombohedral that looks like pyramidal. The prismatic sides usually bear horizontal stripes. It occurs in crystals and solid masses. Quartz is a very common and widespread mineral. It can be found in several igneous and transformed rocks and because it is tough against mechanical and chemical decomposition, it also occurs in many sedimentary rocks and in sand. It has various uses. Its various versions are used as precious and semiprecious stones (amethyst, yellow, agate). The quartz sand is used as abrasive, as well as in glass and silicon bricks industry. In powder, it is used in porcelain and colour industry and as rock (sandstone, quartzite) for construction purposes. It is used in scientific optical instruments (lenses, prisms) and because of its powerful piezoelectric properties, it is used in the manufacture of digital watches and elsewhere. 
Bibliography: Ευρετήριο ορυκτών ΑΠΘ στην ιστοσελίδα http://www.geo.auth.gr/ Τσιραμπίδης Α. (2005). Ο ορυκτός πλούτος της Ελλάδας. Εκδόσεις Γιαχούδη Θεσσαλονίκη, σελ. 391. Berry, L.G., Mason, B. and Dietrich, R.V. (1983). Mineralogy. W. H. Freeman and Company, San Francisco, 561 pp. Σαπουντζής, Η. και Χριστοφίδης, Γ. (1985). Ορυκτοδιαγνωστική. University Studio Press, Θεσσαλονίκη, 241 σ.