Brief Description: Its name is due to its content in sodium. Its chemical formula is (Na4Al3(SiO4)3Cl). Sodalite is a rare mineral. Its colour is blue, white, grey or even green, while its lustre is vitreous or sebaceous. Its crystals are transparent or opaque. The massive samples are opaque. The specific gravity is 2.1 ? 2.3 and its hardness is 5.5 ? 6.0. Sodalite is a member of the feldspathoid group. Feldspathoid are minerals whose chemical types are close to that of alkali feldspars, but have lower content in silica (SiO2) and are aluminium silicates of Na and K. It can be found in rocks poor in silicon that do not contain other mineral also poor in silicon and quartz. If quartz were present during the crystallization, it would react with any feldspathoid and form feldspar (mica). Sodalite is difficult to distinguish from other feldspathoids when it has blue colour. It is the only feldspathoid that contains chloride, which is released when it reacts with thin HNO3. It is used in sculpture and jewels manufacture. 
Bibliography: Ευρετήριο ορυκτών ΑΠΘ στην ιστοσελίδα http://www.geo.auth.gr/106/az_gr.htm Από την ιστοσελίδα http://mineral.galleries.com/minerals/ Τσιραμπίδης Α. (2005). Ο ορυκτός πλούτος της Ελλάδας. Εκδόσεις Γιαχούδη Θεσσαλονίκη, σελ. 391.