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

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.