Crednerite from the Gozaisho Mine, Iwaki City, Fukushima Prefecture, Japan
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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 Cu<SUB>2</SUB>O 47.25, Mn<SUB>2</SUB>O<SUB>3</SUB> 41.78, Fe<SUB>2</SUB>O<SUB>3</SUB> 10.34, total 99.37%, corresponding to Cu<SUB>1.00</SUB>(Mn<SUB>0.80</SUB>Fe<SUB>0.20</SUB>)<SUB>Σ1.00</SUB>O<SUB>2</SUB> on the basis of O=2, or ferrian crednerite. The X-ray powder pattern is indexed on a monoclinic cell with <I>a</I>=5.552Å, <I>b</I>=2.894Å, <I>c</I>=5.899Å, β=104.29°, <I>Z</I>=2. The valence loaded ideal formula is Cu<SUP>1+</SUP>Mn<SUP>3+</SUP>O<SUB>2</SUB>. The mineral is not of secondary but primary formation as a metamorphic mineral under the oxidizing condition, which had annihilated Fe<SUP>2+</SUP> and influenced the chemical compositions of the associated rhodonite and ganophyllite both devoid of FeO despite their capabilities to involve Fe<SUP>2+</SUP>. Also, the metamorphic condition enabled the formation of solid solution containing 20 mole% of CuFeO<SUB>2</SUB>, but this was not attained under the superficial oxidizing condition under which all the known crednerites have been formed.
- Mineralogical Journal
Mineralogical Journal 17(1), 21-27, 1994-01-01
Japan Association of Mineralogical Sciences