Gerstleyite

General Information: Chemical Formula:Na2(Sb,As)8S13·2(H2O) Composition:(Molecular Weight = 1,426.04 gm)Sodium 3.22 % NaAntimony 59.76 % SbArsenic 5.25 % AsHydrogen 0.28 % H Sulfur 29.23 % S Oxygen 2.24 % O  Empirical Formula: Na2Sb7AsS13·2(H2O) Environment:Sedimentary borate deposits. Locality:Baker Mine, Boron, Kern Co. California. Name Origin:Named for J. M. Gerstley (1907-), President, Pacific Coast Borax Company.Physical Properties: Cleavage:[010] Perfect, [100] Perfect, [001] Indistinct Color:vermilion or black. Density:3.62 Habits:Platy - Sheet forms (e.g. micas)., Fibrous - Crystals made up of fibers., Spherical - Spherical, rounded aggregates. Hardness:2.5 - Finger Nail Luster:Adamantine Streak:vermilionMore details...