Three new members of the hakite series, Cu₆(Cu₄<i>Me</i>²⁺₂)Sb₄Se₁₃: hakite-(Cd), hakite-(Fe) and hakite-(Zn) from the Bytíz deposit, uranium and base-metal Příbram ore district, Czech

Abstract Hakite-(Cd), hakite-(Fe) and hakite-(Zn) are new minerals belonging to the tetrahedrite group and forming, along with hakite-(Hg), the hakite series. They have been discovered in samples collected from the Bytíz deposit, in the uranium and base-metal Příbram ore district, Central Bohemia, Czech Republic. They occur as anhedral grains, up to 300 μm in size, in a calcite gangue, associated with clausthalite, cadmoselite, hakite-(Hg) [for hakite-(Cd)], berzelianite, bukovite, bytízite, crookesite, chaméanite, eskebornite, příbramite, the not yet approved giraudite-(Hg) and giraudite-(Cu) , hakite-(Hg), umangite, chalcopyrite, tetrahedrite-(Zn) and a new Cu–As selenide [for hakite-(Fe) and -(Zn)]. The three new species are black, with a metallic lustre. Mohs hardness is ca . 3½–4; calculated density is 6.019 (Hak-Cd), 6.011 (Hak-Fe) and 6.081 g.cm –3 (Hak-Zn). In reflected light, they are isotropic, pale grey with bluish (Hak-Cd) or brownish (Hak-Fe and Hak-Zn) shades. Empirical formulae of hakite-(Cd), hakite-(Fe), and hakite-(Zn) are Cu 9.71 Ag 0.24 Cd 1.51 Hg 0.43 Zn 0.03 (Sb 3.94 As 0.13 ) Σ4.07 Se 11.35 S 1.57 , Cu 10.11 Ag 0.18 Fe 0.81 Zn 0.50 Hg 0.26 (Sb 3.72 As 0.41 ) Σ4.13 Se 12.65 S 0.12 , and Cu 10.03 Ag 0.24 Zn 0.61 Fe 0.53 Hg 0.45 (Sb 3.55 As 0.60 ) Σ4.15 Se 12.82 S 0.08 , respectively. These formulae correspond to the end-member formulae Cu 6 (Cu 4 Cd 2 )Sb 4 Se 13 (Hak-Cd), Cu 6 (Cu 4 Fe 2 )Sb 4 Se 13 (Hak-Fe), and Cu 6 (Cu 4 Zn 2 )Sb 4 Se 13 (Hak-Zn). All these new members of the hakite series are cubic, I $\bar{4}$ 3 m , Z = 2, with unit-cell parameters a = 10.8860(6) Å, V = 1290.0(2) Å 3 (Hak-Cd); a = 10.7983(4) Å, V = 1259.12(14) Å 3 (Hak-Fe); and a = 10.8116(14) Å, V = 1263.8(5) Å 3 (Hak-Zn). These species are isotypic with the other members of the tetrahedrite group, and their crystal structures have been refined on the basis of single-crystal X-ray diffraction data down to R 1 values of 0.0230 (Hak-Cd), 0.0254 (Hak-Fe), and 0.0302 (Hak-Zn). These structural data allow us to describe the S-to-Se partitioning in hakite-series minerals and to understand the mechanisms avoiding too short Me –Se distances in these selenides.