Volborthite

General Information: Chemical Formula:Cu++3V+++++2O7(OH)2·2(H2O) Composition:(Molecular Weight = 474.56 gm)Vanadium 21.47 % V Copper 40.17 % CuHydrogen 1.27 % H Oxygen 37.09 % O  Empirical Formula: Cu3V5+2O7(OH)2·2(H2O)Physical Properties: Cleavage:[???] Imperfect Color:brownish yellow, greenish yellow, yellow, yellow green, or light brown. Density:3.5 Diaphaniety:Translucent to Subtranslucent Habits:Globular - Spherical, or nearly so, rounded forms (e.g. wavellite)., , Hardness:3 - Calcite Luminescence:Non-fluorescent. Luster:Vitreous - Pearly Streak:light greenMore details...