Lazurite

General Information: Chemical Formula:Na3Ca(Al3Si3O12)S Composition:(Molecular Weight = 498.31 gm)Sodium 13.84 % NaCalcium 8.04 % CaAluminum 16.24 % AlSilicon 16.91 % SiSulfur 6.43 % S Oxygen 38.53 % O  Empirical Formula: Na3CaAl3Si3O12S Locality:District of Badakhshan, Afghanistan. Name Origin:From the Persian lazward - "blue."Physical Properties: Cleavage:[110] Imperfect Color:blue, azure blue, violet blue, or greenish blue. Density:2.38 - 2.42, Average = 2.4 Diaphaniety:Translucent Habits:Massive - Granular - Common texture observed in granite and other igneous rock., , Hardness:5.5 - Knife Blade Luminescence:Fluorescent. Luster:Vitreous - Dull Streak:light blueMore details...