jarosewichite

Jarosewichite is a rare manganese arsenate mineral with formula: Mn2+3Mn3+(AsO4)(OH)6. It was first described in Franklin, New Jersey which is its only reported occurrence. Its chemical composition and structure are similar to chlorophoenicite. This mineral is orthorhombic with 2/m2/m2/m point group. Its crystals are prismatic or barrel-shaped. The color of jarosewichite is dark red to black. It has subvitreous luster of fracture surfaces and reddish-orange streak. This mineral occurs with flinkite, franklinite, andradite and cahnite.

==Composition== The chemical composition of jarosewichite was obtained in 1982. These data were obtained by electron microprobe analysis with a voltage of 15 kV and a current of 0.025μA. Manganite(Mn), synthetic olivenite(As), synthetic ZnO(Zn), and hornblende(Ca, Mg, Fe) are used as standards for the analysis. Water percentage of the sample cannot be measured directly because of lacking large size of sample. The composition of jarosewichite is as follows: As2O5 24.0 Mn2O3 17.7 FeO 0.4 MnO 42.3 ZnO 1.2 MgO 2.1 CaO 0.2 H2O 12.1 Total 100.0