Weibullite

General Information: Chemical Formula:Pb6Bi8(S,Se)18 Composition:(Molecular Weight = 3,679.81 gm)Bismuth 45.43 % BiLead 33.78 % PbSelenium 8.58 % SeSulfur 12.20 % S  Empirical Formula: Pb6Bi8S14Se4 Locality:Falun, Sweden. Name Origin:Named for Mats Weibull (1856-1923), Swedish mineralogist.Physical Properties: Cleavage:[???] Good Color:steel gray. Density:6.97 - 7.145, Average = 7.05 Diaphaniety:Opaque Habits:Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline)., Massive - Fibrous - Distinctly fibrous fine-grained forms., Hardness:2-3 - Gypsum-Calcite Luster:Metallic Streak:dark grayMore details...