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Brief Description: Its name derives from its composition. Its chemical formula is FeCr2O4 and it belongs to the Oxides category (spinel group). Its colour ranges from iron-black, brownish-black to pitch-black. It is opaque and its lustre is metallic or semi-metallic. Its specific gravity is 4.5-4.8, its hardness 5½ and its fusibility 7. Its crystals are rarely octahedral and the crystal system is cubic. It usually occurs in solid, granular aggregates. It can be found mainly in ultramafic rocks with olivine, pyroxene, serpentine, uvarovite, magnetite, magnetopyrite, corundum etc and in black sand. It constitutes the fundamental copper ore. 
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.