Ferroglaucophane

General Information: Chemical Formula:[ ]Na2(Fe++3Al2)Si8O22(OH)2 Composition:(Molecular Weight = 878.17 gm)Sodium 5.24 % NaAluminum 6.14 % AlIron 19.08 % FeSilicon 25.59 % SiHydrogen 0.23 % H Oxygen 43.73 % O  Empirical Formula: Na2Fe2+3Al2(Si8O22)(OH)2 IMA Status:Approved IMA 1978Physical Properties: Cleavage:[110] Perfect Color:blue, blue black, gray, or gray blue. Density:3.04 - 3.23, Average = 3.13 Diaphaniety:Transparent to Translucent Hardness:6 - Orthoclase Luster:Vitreous - Dull Streak:blue grayMore details...