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Brief Description: Precious stone consisting of transparent red corundum. The term Ruby derives from the Latin word rubeus (red). Initially, this name referred to other red minerals as well, like turmaline, topaz, spinel, quartz and fluorite. It has the chemical formula Al2O3 and belongs to the category of Oxides. Its lustre is pearly or vitreous. Its specific gravity is 3.9 ? 4.1, its hardness is 9 (one of the highest in Mohs scale) and its fusibility 7. Its crystals are prismatic, ending up in pyramids with distinct horizontal stripes on the prismatic and pyramidal sides. Often, they are rounded or barrel-like. It is usually found in transformed rocks (gneiss, schist) and sometimes in igneous poor in silicon dioxide (syenites). It usually occurs with cyanite, sillimanite, cordierite, micas, tourmaline, magnetite, nepheline, garnet etc. 
Bibliography: Ευρετήριο ορυκτών ΑΠΘ στην ιστοσελίδα http://www.geo.auth.gr/106/az_gr.htm 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.