Brief Description: Zeolites are colourless or white to white-green minerals with board-like to needle-like crystals. Their lustre is vitreous to silky. Their specific gravity is from 2.0 to 2.29 and their hardness ranges, depending on the species, from 3.0 to 5.5. The chemical formula of the zeolites is M2/nO.Al2O3xSiO2.yH2O where M = alkali, n = cation valence, x = number from 2 to 10, y= number from 3 to 7. The quantity of the absorbed water ranges from 10-20% of the absorbed part. This water is constantly shed with heating up to 350 degrees C and taken again with gradual temperature decrease to room temperature. In our days, it has been ascertained that they constitute the most abundant and widest spread authigenic silicon materials in sedimentary rocks. Zeolites are used in detergent and fertilizer manufacture, as indifferent medicaments in pharmaceutical products, as soil additives, fodder supplements and as pets? hygienic sand. 
Bibliography: Ευρετήριο ορυκτών ΑΠΘ στην ιστοσελίδα http://www.geo.auth.gr/106/az_gr.htm Τσιραμπίδης Α. Ο ορυκτός πλούτος της Ελλάδας. Εκδόσεις Γιαχούδη Θεσσαλονίκη, 2005, σελ. 391.