Abstract
Crednerite from the Gozaisho mine occurs as black tablets in close association with Sr-bearing barite in a coarse-grained rhodonite ore with minor quartz, braunite, spessartine, aegirine, and ganophyllite, rarely with långbanite as a product of regional metamorphism. The microprobe analysis gives Cu2O 47.25, Mn2O3 41.78, Fe2O3 10.34, total 99.37%, corresponding to Cu1.00(Mn0.80Fe0.20)Σ1.00O2 on the basis of O=2, or ferrian crednerite. The X-ray powder pattern is indexed on a monoclinic cell with a=5.552Å, b=2.894Å, c=5.899Å, β=104.29°, Z=2. The valence loaded ideal formula is Cu1+Mn3+O2. The mineral is not of secondary but primary formation as a metamorphic mineral under the oxidizing condition, which had annihilated Fe2+ and influenced the chemical compositions of the associated rhodonite and ganophyllite both devoid of FeO despite their capabilities to involve Fe2+. Also, the metamorphic condition enabled the formation of solid solution containing 20 mole% of CuFeO2, but this was not attained under the superficial oxidizing condition under which all the known crednerites have been formed.
