Tennantite-(Hg), Cu6(Cu4Hg2)As4S13, was approved as a new mineral species (IMA2020-063) from the Lengenbach quarry, Imfeld, Binn Valley, Canton Valais, Switzerland. It was identified as an aggregate of black metallic tetrahedral crystals, less than 0.1 mm in size, intimately associated with sinnerite, and grown on realgar. In reflected light, tennantite-(Hg) is isotropic, grey in colour, with creamy tints. Minimum and maximum reflectance data for COM wavelengths in air are [λ (nm): R (%)]: 470: 29.1; 546: 29.1; 589: 28.5; 650: 27.7. Electron microprobe analysis gave (in wt.% – average of 7 spot analyses): Cu 32.57(42), Ag 6.38(19), Tl 0.29(14), Zn 0.04(5), Hg 17.94(2.27), Pb 0.70(51), As 17.83(61), Sb 0.34(8), S 24.10(41), total 100.19(1.04). The empirical formula of the sample studied, recalculated on the basis of ΣMe = 16 atoms per formula unit, is (Cu4.69Ag1.04Tl0.03)Σ5.76(Cu4.35Hg1.58Pb0.06Zn0.01)Σ6.00(As4.20Sb0.05)Σ4.25S13.26. Tennantite-(Hg) is cubic, I$\overline 4$3m, with a = 10.455(7) Å, V = 1143(2) Å3 and Z = 2. The crystal structure of tennantite-(Hg) has been refined by single-crystal X-ray diffraction data to a final R1 = 0.0897 on the basis of 214 unique reflections with Fo > 4σ(Fo) and 22 refined parameters. Tennantite-(Hg) is isotypic with other members of the tetrahedrite group. Mercury is hosted at the tetrahedrally coordinated M(1) site, in accord with the relatively long M(1)–S(1) distance (2.389 Å), similar to that observed in tetrahedrite-(Hg). Minor Ag is located at the triangularly-coordinated and split M(2) site. Other occurrences of tennantite-(Hg) are briefly reviewed and the Lengenbach finding is described within the framework of previous knowledge about the Hg mineralogy at this locality.

The new mineral species ralphcannonite, AgZn2TlAs2S6, was discovered in the Lengenbach quarry, Binn Valley, Wallis, Switzerland. It occurs as metallic black equant, isometric to prismatic crystals, up to 50 μm, associated with dufrénoysite, hatchite, realgar and baryte. Minimum and maximum reflectance data for COM wavelengths in air are [λ (nm): R (%)]: 471.1: 25.8/27.1; 548.3: 25.2/26.6; 586.6: 24.6/25.8; 652.3: 23.9/24.8. Electron microprobe analyses give (wt.%): Cu 2.01(6), Ag 8.50(16), Zn 10.94(20), Fe 3.25(8), Hg 7.92(12), Tl 24.58(26), As 18.36(19), Sb 0.17(4), S 24.03(21), total 99.76(71). On the basis of 12 atoms per formula unit, the chemical formula of ralphcannonite is Ag0.63(2)Cu0.25(2)Zn1.35(5)Fe0.47(1)Hg0.32(2)Tl0.97(3)[As1.97(6)Sb0.01(1)]Σ1.98(5)S6.03(8). The new mineral is tetragonal, space group I42m, with a = 9.861 (2), c = 11.125(3) Å, V = 1081.8(4) Å3, Z = 4. The main diffraction lines of the calculated powder diagram are [d (in Å), intensity, hkl]: 4.100, 85, 211; 3.471, 40, 103; 2.954, 100, 222; 2.465, 24, 400; 2.460, 39, 303. The crystal structure of ralphcannonite has been refined by X-ray single-crystal data to a final R1 = 0.030, on the basis of 140 observed reflections [Fo > 4σ(Fo)]. It shows a three dimensional framework of (Ag,Zn)-centred tetrahedra (1 M1 + 2 M2), with channels parallel to [001] hosting TlS6 and (As,Sb)S3 disymmetric polyhedra. Ralphcannonite is derived from its isotype routhierite M1CuM2Hg2TlAs2S6 through the double heterovalent substitution M1Cu+ + M2Hg2+ → M1Zn2+ + M2Ag+. This substitution obeys a steric constraint, with Ag+, the largest cation relative to Zn2+ and Cu+, entering the largest M2 site, as observed in arsiccioite. The ideal crystal-chemical formula of ralphcannonite is M1ZnM2(Zn0.5Ag0.5)2TlAs2S6.

The new mineral species ferrostalderite, CuFe2TlAs2S6, was discovered in the Lengenbach quarry, Binn Valley, Wallis, Switzerland. It occurs as minute, metallic, black, equant to prismatic crystals, up to 50 mu;m, associated with dolomite, realgar, baumhauerite (?) and pyrite. Minimum and maximum reflectance data for COM wavelengths in air are [λ (nm): R (%)]: 471.1: 24.2/25.4; 548.3: 23.7/24.7; 586.6: 22.9/23.8; 652.3: 21.0/22.0. Electron microprobe analyses give (wt.%): Cu 6.24(25), Ag 4.18(9), Fe 9.95(83), Zn 4.46(91), Hg 1.22(26), Tl 26.86(62), As 19.05(18), Sb 0.63(6),S 25.39(47), total 97.98(72). On the basis of 12 atoms per formula unit, the chemical formula of ferrostalderite is Cu0.75(2)Ag0.30(1)Fe1.36(10) Zn0.52(11) Hg0.05(1) Tl1.00(1)[As1.94(4)Sb0.04(1)]∑1.98(4)S6.04(4). The new mineral is tetragonal, space group I4̄2 m, with a = 9.8786(5), c = 10.8489(8) Å, V = 1058.71(11) Å3, Z = 4. The main diffraction lines of the calculated powder diagram are [d (in Å), intensity, hkl]: 4.092, 70, 211; 3.493, 23, 220; 3.396, 35, 103; 3.124, 17, 310; 2.937, 100, 222; 2.656, 19, 321; 2.470, 19, 400; 2.435, 33, 303. The crystal structure of ferrostalderite has been refined by Xray single-crystal data to a final R1 = 0.050, on the basis of 1169 reflections with F0 > 4σ(F0). It shows a three dimensional framework of (Cu,Fe)-centred tetrahedra (1M1 + 2 M2), with channels parallel to [001] hosting disymmetric TlS6 and (As,Sb)S3 polyhedra. Ferrostalderite is derived from its isotype stalderite M1CuM2Zn2TlAs2S6 through the homovalent substitution M2Zn2+ → M2Fe2+. The ideal crystal-chemical formula of ferrostalderite is M1CuM2Fe2TlAs2S6.