As-bearing renierite from the Higashimatazawa Kuroko deposit of the Furutobe mine, Akita prefecture, occurs as microscopic grains in association with tennantite, bornite, occasionally galena and chalcopyrite or inclusion in them, accompanied by large blocks of Yellow Ore composed of pyrite and minor tennantite in dacitic tuff belonging to Lower Formation of middle Miocene. It is brownish orange in polished section with distinct anisotropism between crossed polars and the interference colors change from orange to bluish gray. No etching reactions with ordinary reagents were observed. The reflectances measured at 586, 546, 497, 436, and 406 nm are: 30.1-32.8, 25.8-26.3, 21.8-22.6, 18.1-19.0, 19.8-21.1%, respectively. Vickers hardness (25g load) ranges VHN 290-340kg/mm
2, The X-ray powder pattern consists of the lines corresponding to stronger lines in the pattern of renierite from the Kipushi mine, Zaire, and is indexed on a tetragonal cell with a=10.57 (1), c=10.57 (1) Å. The average of seven microprobe analyses is: Cu 44.5, Fe 13.4, Zn 0.5, Ge 4.2, Sn 0.3, As 4.9, S 32.8, Total 100.6%, corresponding to Cu
2.68Fe
0.91Zn
0.03Ge
0.22Sn
0.01As
0.25S
3.90 on the basis of 8 atoms per molecule.
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