Macfallite

General Information: Chemical Formula:Ca2(Mn+++,Al)3(SiO4)(Si2O7)(OH)3 Composition:(Molecular Weight = 542.26 gm)Calcium 14.78 % CaManganese 25.33 % MnAluminum 2.49 % AlSilicon 15.54 % SiHydrogen 0.56 % H Oxygen 41.31 % O  Empirical Formula: Ca2Mn3+2.5Al0.5(SiO4)(Si2O7)(OH)3 Environment:Associated with other Mn-silicates. IMA Status:Approved IMA 1979 Locality:Manganese Lake, Copper Harbor, Keweenaw County, Michigan, USA. Name Origin:Named for Russell P. MacFall, a dedicated amateur mineralogist.Physical Properties: Cleavage:[001] Perfect Color:brown, maroon, reddish brown, or pink. Density:3.43 Habits:Acicular - Occurs as needle-like crystals., Aggregates - Made of numerous individual crystals or clusters., Twinning Common - Crystals are usually twinned. Hardness:5-5.5 - Apatite-Knife Blade Luster:Vitreous - Silky Streak:brownMore details...