Description: The condensed-phase system Cu–Pd–Se was investigated by means of dry syntheses from elements in evacuated silica glass tubes at 650 °C, 550 °C, 400 °C, and 300 °C. Synthetized phases were analysed by electron microprobe and textural studies in polished sections. At 650 °C an extensive selenide liquid field covers central portions of the system, coexisting with a limited choice of Pd selenides, Cu 2– x Se, alloys, and a (Cu,Pd)Se 2 solid solution. The selenide melt recedes to the Pd side of the system at 550 °C and its remnants persist at 400 °C. At the lower temperature, the gamut of Pd selenides becomes richer, and especially Pd 4 Se and Pd 17 Se 15 display significant solubility of Cu. The composition range of (Cu,Pd)Se 2 broadens and moves towards Cu-richer compositions as temperature decreases; CuSe and CuSe 2 appear at 300 °C. The synthetic analogue of jaguéite, Cu 2 Pd 3 Se 4 , is present at 400 °C and 300 °C, at Se concentrations above the Cu 2– x Se–Pd 17 Se 15 line. At all examined temperatures, the individualized CuPd alloy dissolves Se, up to ~5 at% at low temperatures.

Description: Detailed electron-microprobe investigations and crystal-structure determinations established that ‘sartorite’ represents a group of distinct mineral species, each with unique chemistry and crystal structure. These manifest themselves as the 7-, 9- and 11-fold P 2 1 / c superstructures of the basic 4.2 Å substructure. Heptasartorite is Tl 7 Pb 22 As 55 S 108 [based on 192 atoms per formula unit ( apfu ), 84Me + 108S] with a = 29.269(2), b = 7.8768(5), c = 20.128(2) Å, β = 102.065(2)° and unit-cell volume V = 4537.8 Å 3 ; enneasartorite is Tl 6 Pb 32 As 70 S 140 (based on 248 apfu , 108Me + 140S) with a = 37.612(6), b = 7.8777(12), c = 20.071(3) Å, β = 101.930(2)° and V = 5818.6(15) Å 3 ; hendekasartorite is Tl 2 Pb 48 As 82 S 172 (based on 304 apfu , 132Me + 172S) (empirical Me = 132.48) with a = 31.806(5), b = 7.889(12), c = 28.556(4) Å and β = 99.034(2)° with V = 7076.4(15) Å 3 . Physical and optical properties (grey with metallic lustre, in polished section white with visible bireflectance, red internal reflections; reflectance curves span 28.7–42.5%; Mohs hardness 3–31/2) of these phases are very similar so that chemical analysis and/or single-crystal X-ray diffraction is needed to distinguish them. A brief description of complicated As m S n crank-shaft chains in the walls of double-ribbons which form the As-based slabs of these structures is given. The three new mineral species differ in their structures by 4.2 Å modular increments, not just by cation substitutions. They represent anion-omission derivatives of the ‘ideal’ PbAs 2 S 4 composition with an important role for thallium in charge compensation. The described minerals belong to the late sulfide phases in the Pb–Tl–Ag–As deposit of Lengenbach, Wallis, Switzerland.

Description: Écrinsite, ideally AgTl 3 Pb 4 As 11 Sb 9 S 36 , is a new thallium sulphosalt species found in the Jas Roux As–Sb–Pb–Tl–Hg–Ag deposit, Parc national des Écrins, Département des Hautes-Alpes, France. Associated minerals in four different samples are jasrouxite, stibnite, smithite, guettardite, chabournéite, pierrotite and As-bearing zink enite. Écrinsite is opaque with metallic lustre. It is brittle without any discernible cleavage and with conchoidal fracture. In reflected light écrinsite is white, pleochroism is not discernible. Internal reflections are absent. In crossed polarisers, anisotropism is distinct, with rotation tints in shades of grey. The reflectance data (%, air) are: 37.3, 38.6 at 470 nm, 35.2, 36.7 at 546 nm, 34.0, 35.5 at 589 nm and 32.0, 33.3 at 650 nm. Mohs hardness is 3–31/2, microhardness VHN 25 is in the range 175–201, with a mean value of 189 kg mm –2 . Average results of 20 electron-microprobe analyses for the structurally investigated grain are (in wt%): Ag 2.03(10), Cu 0.02(1), Tl 14.57(20), Pb 16.23(32), Sb 23.97(25), As 17.87(17), S 25.20(15), total 99.88 (15), corresponding to Ag 0.87 Cu 0.02 Tl 3.28 Pb 3.61 Sb 9.06 As 10.98 S 36.19 (on the basis of 28 Me + 36S = 64 apfu ). The simplified formula, AgTl 3 Pb 4 Sb 9 As 11 S 36 , is in accordance with the results of the crystal-structure analysis and may be derived from the ideal baumhauerite formula, Pb 12 As 16 S 36 , by substitution of Sb for As and [(Tl,Ag) + + (As,Sb) 3+ ] 2Pb 2+ . The density, 4.96 g cm –3 , was calculated using the ideal formula. Écrinsite has a triclinic cell, space group P 1, with a = 8.080(2), b = 8.533(2), c = 22.613(4) Å, α = 90.23(3) ° , β = 97.17(3) ° , = 90.83(3) ° , V = 1546.7(6) Å 3 , and Z = 1. The strongest five lines in the (calculated) powder-diffraction pattern are [ d in Å ( I )( h k l )]: 4:14(68)(1 0 5), 3.72(92)(1 0 5), 3:56 N (100)(1 0 6); 3:53(80) (1 2 2) and 3.48(72)(1 2 2). Écrinsite is a new member of the sartorite homologous series with 1,2 = 3, 4, i.e ., N = 3.5. Four other members share the same N value as écrinsite: baumhauerite, argentobaumhauerite, boscardinite and bernarlottiite. By comparison to the closely related boscardinite (ideally Tl 2 Pb 8 Sb 14 As 4 S 36 ), écrinsite is characterised by both an excess of As over Sb and a distinctly higher substitution of [(Tl,Ag) + (As,Sb) 3+ ] 2Pb 2+ . Baumhauerite and bernarlottiite are basically unsubstituted members, whereas argentobaumhauerite has a Ag substitution, without Tl.

Description: Jasrouxite, Ag 16 Pb 4 (Sb 25 As 15 ) 40 S 72 , is triclinic, space group P- 1, lattice parameters a = 8.2917(5), b = 19.101(1), c = 19.487(1) Å, α = 89.731(1)°, β = 83.446(1)°, and = 89.944(1) °. Unit-cell volume is V = 3066.1(3) Å 3 , Z = 1 for the title formula. It is the N =4 member of the lillianite homologous series of modular structures created by unit-cell twinning of (311) slabs of the PbS archetype. The structure contains 30 independent cation sites, from which 12 are mixed sites, and 36 independent sulphur sites ( i.e . six times the sites of the lillianite-like subcell). Only the c parameter copies that of lillianite, a is doubled and b is about 3/2 of a diagonal to (001) of lillianite. In agreement with the "2Pb-〉 Ag + (Sb,As) oversubstitution" against ideal PbAgSb 3 S 6 , the trigonal prismatic sites on composition planes of twinning are occupied by two Pb-Sb rows and one Sb-Sb row, and the PbS-like slabs contain excess number of Ag sites. Unlike lillianite, the alternating (311) PbS slabs are non-equivalent and each of them has two types of differently occupied diagonal planes of atoms, always present in a 2:1 ratio. This results in triclinic symmetry with only small distortions from monoclinic metrics. In both slab types lone electron pairs of As and Sb congregate in large micelles with elliptic cross-section. Among lillianite homologues, jasrouxite exhibits hitherto unseen complications of cation ordering, resulting from the presence of two distinct metalloids in the structure, oversubstitution by (Ag + M 3+ ), and highly expressed lone electron pair activity of trivalent cations.

Description: The thallium-rich sulfosalt deposit of Jas Roux, situated in the Pelvoux Massif (Hautes-Alpes département , France), occurs in a Triassic sedimentary series. Jasrouxite belongs to the early lead-containing stages of the Tl–As–Sb period of mineralization. It occurs in a silicified gangue, along with smithite and late realgar. Jarouxite forms dark gray anhedral grains with metallic luster, up to several millimeters in size, as well as aggregates of grains which range to more than 10 mm in diameter. From their surface, grains of jasrouxite are embayed by a three-phase myrmekite aggregate composed of stibnite, boscardinite and smithite. The mineral is brittle, with irregular fracture; no cleavage or parting was observed. In reflected light, color is off-white. Bireflectance is weak, in off-white tones; anisotropy is distinct. Rare straight twin lamellae occur in otherwise untwinned crystals. The empirical formula, on the basis of 132 apfu derived from the crystal-structure determination, is Cu 0.79 Ag 14.64 Pb 4.10 T l0.05 As 15.37 Sb 24.87 S 72.18 . Calculated density is 4.87 g.cm –3 . The simplified formula is Ag 16 Pb 4 (Sb 25 As 15 ) 40 S 72 ; the only notable variation is the partial substitution AsSb. Jasrouxite is triclinic, space group P -1. Lattice parameters are a 8.2917(5) Å, b 19.101(1) Å, c 19.487(1) Å, α 89.731(1)°, β 83.446(1)°, 89.944(1)°, V 3066.1(3) Å 3 , Z= 1 for Ag 16 Pb 4 (Sb 24 As 16 ) 40 S 72 . Jasrouxite is a member of the lillianite homologous series, its order number is 4 and degree of Ag + (Sb, As) 2 Pb substitution is 36.5 % above the theoretical 100 % substitution expressed as PbAg(Sb,As) 3 S 6 . The most important features of the crystal structure are: substantial replacement of lead in selected trigonal prismatic sites by Sb, formation of a string of large volumes for accommodation of lone electrons of Sb and As in the central portions of galena-like slabs, and high contents of Ag and (Sb,As).

Description: Chovanite, a new representative of the group of oxysulphosalts of Pb and Sb was found in three hydrothermal deposits of antimony ore, Dúbrava, Malé Zelezné, and Klacianka, situated on the northern slopes of the Low Tatra Mountains, Slovakia. It is associated with other Pb–Sb sulphosalts, especially boulangerite, robinsonite and dadsonite. In reflected light, chovanite is white, bireflectance is distinct already in air. Pleochroism is present; colour varies from white with a yellowish green tint (darkest position) to white with a faint bluish tint (lightest position). Reflectance values in air are R max – R min (%) ( nm): 43.6–37.7 (470), 43.0–36.7 (546), 41.3–35.4 (589), 39.2–34.0 (650). Anisotropy is moderate to strong both in air and in oil, with blue grey to brown grey polarization colours. Internal reflections and twinning are absent. The optical properties are very similar to boulangerite. Micro-indentation hardness is 222.5 with a range 213–238. Derived Mohs hardness is 3. Cleavage is good, parallel to the c axis. Simplified chemical formula based on electron-microprobe analyses is Pb 14.42(35) Sb 14.33(11) S 36.04(23) , Z = 4, which corresponds to Pb 50.74, Sb 29.63, S 19.62, total 100.00 wt%. No other elements exceed detection limits; chlorine is absent and oxygen was not measured. Structural formula is Pb 15–2 x Sb 14+2 x S 36 O x ( Z = 4) for which the above mean of microprobe measurement data and the structure refinement give the value of x equal to ~0.2. Density (calc.) is 7.14 g/cm 3 . Crystal system is monoclinic, space group C 2/ m, lattice parameters a = 48.189(48) Å, b = 4.1104(40) Å, c = 34.235(35) Å, β = 106.059(15)°, V = 6517(11) Å 3 , Z = 4. Chovanite belongs to a sulphosalt family of boxwork structures, together with pellouxite, scainiite, pillaite, marruccite, vurroite, neyite, and several synthetic sulphosalts. Its crystal structure contains 11 independent lead sites, 13 coordination polyhedra of antimony, some of them with Sb sites split into two partially occupied non-overlapping positions, and five mixed Pb, Sb sites. The boxwork structure of chovanite is formed by a combination of three types of structural modules: (a) continuous walls with a complex structure of rod-layer type; these walls are interconnected by (b) rod-like partitions, and the resulting box-like channels (c) are filled by still another type of structure rods. Chovanite has the largest box-like channel system and infill elements known at present. In spite of differences in chemical composition, chovanite is structurally closest to pellouxite (Cu,Ag) 2 Pb 21 Sb 23 S 55 ClO which has a moderately large boxwork channel system.