Arfvedsonite

General Information: Chemical Formula:NaNa2(Fe++4Fe+++)Si8O22(OH)2 Composition:(Molecular Weight = 958.89 gm)Sodium 7.19 % NaIron 29.12 % FeSilicon 23.43 % SiHydrogen 0.21 % H Oxygen 40.04 % O  Empirical Formula: Na3Fe-2+4Fe-3+(Si8O22)(OH)2 Environment:Igneous syenites and pegmatites. IMA Status:Approved IMA 1978 Locality:Boulder Co., Colorado. Name Origin:Named after the Swedish chemist, J. A. Arfvedson (1792-1841).Physical Properties: Cleavage:[110] Perfect, [???] Imperfect Color:black, grayish green, or bluish gray. Density:3.44 - 3.45, Average = 3.44 Diaphaniety:Translucent to opaque Habits:Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite), Fibrous - Crystals made up of fibers., Stellate - Occurs as spherical, radial aggregates radia ting from a "star" like point. Hardness:5.5-6 - Knife Blade-Orthoclase Luminescence:Non-fluorescent. Luster:Vitreous (Glassy) Streak:bluish grayMore details...

General Information: Chemical Formula:NaNa2(Mg4Fe++)Si8O22(OH)2 Composition:(Molecular Weight = 832.72 gm)Sodium 8.28 % NaMagnesium 11.67 % MgIron 6.71 % FeSilicon 26.98 % SiHydrogen 0.24 % H Oxygen 46.11 % O  Empirical Formula: Na3Mg4Fe3+(Si8O22)(OH)2 IMA Status:Approved IMA 1978Physical Properties: Color:black or gray. Density:3.17 Diaphaniety:Subopaque Hardness:5-6 - Between Apatite and Orthoclase Luster:Vitreous (Glassy)More details...

Na3(Fe,Mg)4FeSi8O22(OH)2