Horomanite, (Fe,Ni,Co,Cu)9S8, and samaniite, Cu2(Fe,Ni)7S8, new mineral species from the Horoman peridotite massif, Hokkaido, Japan

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Horomanite and samaniite are found in the interstices among grains of silicate minerals in lherzolite from the Horoman peridotite massif, Samani-cho, Hokkaido, Japan. The mean analytical data for the horomanite, as determined by electron-probe micro-analysis (EPMA), are Cu: 0.43, Fe: 41.82, Ni: 23.76, Co: 0.52 and S: 33.29 for a total of 99.82 wt%. The empirical formula is (Fe5.77Ni3.12Co0.07Cu0.05)Σ9.01S8.00. Crystallographic data for the horomanite acquired by X-ray single-crystal (precession) and powder (Gandolfi) diffraction methods. They revealed a tetragonal symmetry, space group P4/mmm, a = 8.707 Å, c = 10.439 Å, V = 791.4 Å3, and Z = 4.The mean chemical composition of samaniite obtained by EPMA is Cu: 16.90, Fe: 34.60, Ni: 15.48, Co: 0.16, and S: 32.87 for a total of 100.01 wt%. The empirical formula is Cu2.08(Fe4.84Ni2.06Co0.02)Σ6.92S8.00. The crystallographic data for samaniite, which were obtained by X-ray single-crystal and powder-diffraction methods, are tetragonal symmetry, space group P42/mnm, a = 10.089, c = 10.402Å, V = 1058.9Å3, and Z = 4.