Hauyne

General Information: Chemical Formula:(Na,Ca)4-8Al6Si6(O,S)24(SO4,Cl)1-2 Composition:(Molecular Weight = 1,032.43 gm)Sodium 8.91 % NaCalcium 7.76 % CaAluminum 15.68 % AlSilicon 16.32 % SiSulfur 9.32 % S Chlorine 1.72 % ClOxygen 40.29 % O  Empirical Formula: Na4Ca2Al6Si6O22S2(SO4)Cl0.5 Environment:Igneous rocks low in silica and rich in alkalies. Locality:Vesuvian lavas, on Mte Somma, Italy. Name Origin:Named after the French crystallographer, R. J. Hauy (1743-1822).Physical Properties: Cleavage:[110] Perfect, [011] Perfect, [101] Perfect Color:blue, green, red, yellow, or gray. Density:2.4 - 2.5, Average = 2.45 Diaphaniety:Subtransparent to translucent Habits:Crystalline - Coarse - Occurs as well-formed coarse sized crystals., Twinning Common - Crystals are usually twinned., Euhedral Crystals - Occurs as well-formed crystals showing good e xternal form. Hardness:5-6 - Between Apatite and Orthoclase Luminescence:None. Luster:Vitreous - Greasy Streak:bluish whiteMore details...