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[Ag6]4+ clusters are extremely rare in nature (only found in Ag-rich tetrahedrite group minerals). Due to their remarkable structures and some promising applications, a few synthesis phases that contain octahedral [Ag6]4+ clusters have been reported. However, the kinds of natural conditions that promote the formation of subvalent hexasilver clusters in tetrahedrite group minerals are still unclear. Kenorozhdestvenskayaite-(Fe), ideally Ag6(Ag4Fe2)Sb4S12□ is a new tetrahedrite group mineral containing a natural [Ag6]4+ cluster, found in the Yindongpo gold deposit, Weishancheng ore field, Henan Province, China. This new species occurs at the edges of galena crystals as anhedral grains of 2 to 20 μm in size and is associated with pyrargyrite, pyrrhotite, and siderite. Kenorozhdestvenskayaite-(Fe) is black in color with metallic luster. It is brittle with conchoidal fracture and has a calculated density of 5.329 g/cm3. The empirical formula calculated on the basis of cation = 16 apfu is M(2)Ag6M(1)(Ag2.41Cu1.20Fe1.84Zn0.71)Σ6.16X(3)(Sb3.82As0.01)Σ3.83S(1)S11.60S(2)□. It is cubic, with space group I 4 3m, a = 10.7119(6) Å, V = 1229.1(2) Å3, and Z = 2. Since kenorozhdestvenskayaite-(Fe) is a new tetrahedrite group mineral containing a natural [Ag6]4+ cluster, its structure is comparable to the synthetic ternary phosphide (Ag6M4P12) M 6 ′ . The presence of the unusual mineral assemblages, i.e., pyrrhotite and pyrargyrite, as well as the other keno-end-member tetrahedrites, indicates a low-fS2 state for the mineralization stage, probably a result of the fluid boiling process in an open system that likely contributed to the formation of S-deficient tetrahedrites. [ABSTRACT FROM AUTHOR]