ALBERT

Description: The members of the sartorite homologous series are complex sulfides $$M{e}_{8\mathrm{N}-16-2\mathrm{X}}^{2+}$$ Me 3+ 16+X $$M{e}_{\mathrm{X}}^{+}$$ S 8N+8 where Me 2+ is Pb and Me 3+ is As and Sb, whereas Me + is Ag and/or Tl. This paper presents calculation formulae for the homologue order N and for the separate substitution percentages for Tl + (As,Sb) 2Pb and Ag + (As,Sb) 2Pb substitutions. This enables one to evaluate the crystal chemistry and build a systematic classification of the sartorite homologues.

Description: The layer-like crystal structure of franckeite from the mine of San Jose, Bolivia, exhibits a pronounced one-dimensional transversal wave-like modulation and a non-commensurate layer match in two dimensions. It consists of alternating pseudohexagonal (H) layers and pseudotetragonal (Q) slabs and forms a homologous pair with cylindrite, which has thinner Q slabs. The Q slabs in franckeite are four atomic layers thick. The two components have their own lattices and a common modulation. The Q slab of the refined franckeite structure, Pb21.74Sn9.34Fe3.95Sb8.08S56.87, is an MS layer (M = Pb2+, Sn2+, Sb3+) four atomic planes thick, with a = 5.805(8), b = 5.856(16) A, and the layer-stacking vector c = 17.338(5) A. The lattice angles are = 94.97(2){degrees}, {beta} = 88.45(2){degrees}, {gamma} = 89.94(2){degrees}; the modulation vector q = -0.00129(8) a* + 0.128436(10) b* - 0.0299(3) c*. The H layer is a single-octahedron MS2 layer (M = Sn4+, Fe2+) with a = 3.665(8), b = 6.2575(16), c = 17.419(5) A, = 95.25(2){degrees}, {beta} = 95.45(2){degrees}, {gamma} = 89.97(2){degrees}; the modulation vector is q = -0.00087(8) a* + 0.13725(16) b* - 0.0314(4) c*. The a and b vectors of both subsystems are parallel; the c vectors diverge. (3+2)D superspace refinement was performed in the superspace group C[IMG]f1.gif" ALT="1" BORDER="0"〉, using 7397 observed reflections. It resulted in the overall R(obs) value equal to 0.094. The Q slabs are composed of two tightly bonded double-layers, separated by an interspace hosting non-bonding electron pairs. Average composition of cations on the outer surface was refined as Pb0.74(Sn,Sb)0.26, whereas that of cations, which are adjacent to the interspace with lone electron pairs, with a configuration analogous to that observed in orthorhombic SnS, corresponds to (Sn,Sb)0.73Pb0.27. Iron is dispersed over the octahedral Sn4+ sites in the H layer. Transversal modulation of the Q slab is achieved by local variations in the Pb:(Sn,Sb) ratios at its surface and interior. Its purpose is to re-establish a one-dimensional commensurate contact along [010] between the curved Q and H surfaces to the greatest extent possible. Layer-stacking disorder and divergence of the Q and H stacking directions, and the divergence between modulation wave-front and these stacking directions are typical for the composite structures of franckeite and cylindrite. Because of the increased rigidity of the Q component, franckeite usually forms masses of curved crystals rather than cylindrical aggregates. The existence of this family depends critically on the radius ratios of the cations involved, especially those involving (Pb2+, Sn2+) and Sn4+. Their replacement by a Pb2+:Bi3+ combination leads to misfit layer structures of a very different type, typified by cannizzarite.

Description: Ferdowsiite is a member of a mineral association subsidiary to the principal metamorphic minerals of the Barika ore deposit in NW Iran. The empirical formula of ferdowsiite (based on 32 apfu , 16Me + 16S) is Ag 7.97 Pb 0.08 Sb 4.75 As 3.15 Bi 0.01 S 16.04. The crystal-structure formula is Ag 8 (Sb 5.49 As 2.51 ) 8 S 16 ; the simplified formula is Ag 8 (Sb 5 As 3 ) 8 S 16 . The slightly plumbian variety of ferdowsiite has the idealized formula Pb 2x Ag 4–x Sb 3–x AsS 8 with x =~0.2. Ferdowsiite is monoclinic, space group P 2 1 / n , a 8.677(2) Å, b 5.799(1) Å, c 13.839(3) Å, β 96.175(4)°, V 692.28(10) Å 3 , Z = 1 for the formula Ag 8 (Sb 5 As 3 ) 8 S 16 . Calculated powder X-ray data are listed; main diffraction lines are [ d calc ( I rel ) ( hkl )]: 3.225 (96)(113); 3.205 (100)(12); 2.8995 (78)(020); 2.7559 (90)(301); 2.7073 (79)(05); 1.9401 (22)(206); 1.9226 (22)(04). Plumbian ferdowsiite has the same space group, P 2 1 / n. It has a 8.746(7) Å, b 5.805(4) Å, c 13.929(10) Å, β 96.236(11)°, unit cell volume 703.05 Å 3 . The mineral is greyish black, opaque, with dark grey streak and metallic luster. It is brittle with irregular fracture; no cleavage or parting was observed. Calculated density is 5.3 g/cm 3 . In reflected light ferdowsiite is greyish white. Internal reflections are not observable. Pleochroism is distinct, white to grey. Bireflectance is distinct; reflectance values are [(nm), R min ,R max ]: 470, 34.9, 37.3; 546, 33.4, 35.9; 589, 32.4, 35.1; 650, 30.7, 33.5. Anisotropism is distinct and rotation tints vary between dark brown and bluish grey. Ferdowsiite is associated with large corroded crystals of arsenquatrandorite and is partly replaced by guettardite. It also corrodes smithite. Ferdowsiite is often associated with tetrahedrite/tennantite and forms worm-like symplectites with it. This symplectite is partly replaced on the surface by guettardite. Ferdowsiite is one more member of the group of ABX 2 -type sulfosalts of silver, combining antimony and arsenic, with a crystal structure different from other members of this group. The closest crystallographic and structural affinity is to the ternary sulfosalt diaphorite.

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: 〈span〉Hyršlite, Pb〈sub〉8〈/sub〉As〈sub〉10〈/sub〉Sb〈sub〉6〈/sub〉S〈sub〉32〈/sub〉, is a new member of the sartorite homologous series of Pb–(As,Sb) sulfosalts. It occurs in the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. Compositionally it lies between guettardite and twinnite on the one hand, and hendekasartorite on the other hand. Hyršlite is grey, opaque with metallic lustre. It is brittle, without observable cleavage or parting. Mohs hardness is derived as 4, based on VHN〈sub〉25〈/sub〉 range of microhardness (202–221, mean 215 kg mm〈sup〉−2〈/sup〉). Density (calc.) = 5.26 g cm〈sup〉−3〈/sup〉 using a simplified chemical formula. Reflectance percentages (〈span〉R〈/span〉〈sub〉min〈/sub〉 and 〈span〉R〈/span〉〈sub〉max〈/sub〉) for the four standard COM wavelengths are 32.6, 39.0 (470 nm), 32.1, 38.5 (546 nm), 31.5, 37.9 (589 nm), and 30.7, 36.7 (650 nm), respectively. The formula based on 32 S atoms per formula unit (〈span〉apfu〈/span〉) is Pb〈sub〉7.90〈/sub〉Sb〈sub〉5.98〈/sub〉As〈sub〉10.00〈/sub〉S〈sub〉32〈/sub〉. The unit cell of hyršlite was refined from single-crystal data, with monoclinic symmetry, space group 〈span〉P〈/span〉2〈sub〉1〈/sub〉〈span〉a〈/span〉 = 8.475(3) Å, 〈span〉b〈/span〉 = 7.917(3) Å, 〈span〉c〈/span〉 = 20.039(8) Å, β = 102.070(6)〈sup〉o〈/sup〉, 〈span〉V〈/span〉 = 1314.8(9) Å〈sup〉3〈/sup〉. The crystal structure of hyršlite contains 12 independent cation and 16 distinct sulfur sites. There are four fully occupied Pb sites, two fully occupied As sites, one Sb site and five mixed (As,Sb) sites. In projection parallel to the 8.5 Å axis, the crystal structure is a typical member of the sartorite homologous series, a sartorite homologue 〈span〉N〈/span〉 = 3;3, and homeotype of twinnite and guettardite. Opposing surfaces of the tightly bonded double-layer in the (As,Sb)-rich slabs of the structure have different cation configurations – one resembles coordinations observed in guettardite but the opposite one, with (As,Sb) cation pairs and single polyhedra, appears unique among sartorite homologues.〈/span〉

Description: Cairncrossite is a new phyllosilicate species found in manganese ore on dumps of the Wessels Mine, Kalahari Manganese Field, South Africa. Associated minerals are richterite, sugilite, lizardite and fibrous pectolite. It occurs as radiating platy micaceous aggregates of up to 1 cm in size. Cairncrossite is colourless, appearing white, and the crystals are translucent to transparent with a white streak and vitreous to pearly lustre. The crystals are sectile before brittle fracture, with a Mohs hardness of 3. A perfect cleavage parallel (001) is observed. The calculated density is 2.486 g cm –3 . The mineral is biaxial positive with n α = 1.518(2), n β = 1.522(2), n = 1.546(2), 2 V obs = 33.9(6)° (2 V calc = 44.97°) at 589.3 nm and 24°C. The orientation of the indicatrix is Z ^ c * = 10°. The dispersion is weak ( r 〈 v ) and no pleochroism is observed. An intense light-blue fluorescence is emitted under shortwave UV radiation. Cairncrossite is triclinic, space group P $$\overline{1}$$ , a = 9.6265(5), b = 9.6391(5), c = 15.6534(10) Å, α = 100.89(1), β = 91.27(1), = 119.73(1)°, V = 1227.08(13) Å 3 , Z = 1. The strongest lines in the Gandolfi X-ray powder-diffraction pattern [ d in Å( I )( hkl )] are 15.230 (100)(001), 8.290 (15)(1–10), 5.080(25)(003), 3.807(30)(004), and 3.045(20)(005). The chemical composition obtained by electron-microprobe analysis is Na 2 O 3.06, K 2 O 0.11, CaO 18.61, SiO 2 54.91, SrO 11.75, total 88.44 wt%. The relevant empirical formula, based on 16 Si atoms per formula unit ( apfu ) and TGA data is: Sr 1.99 K 0.02 Ca 5.81 Na 1.73 Si 16 O 55.84 H 30.33 . Taking variable sodium contents into account, the idealized structural formula is Sr 2 Ca 7–x Na 2x (Si 4 O 10 ) 4 (OH) 2 (H 2 O) 15–x with 0 ≤ x ≤ 1, and the simplified formula for sodium-rich crystals is SrCa 3 Na(Si 4 O 10 ) 2 (OH)(H 2 O) 7 with Z = 2. The structure of cairncrossite was refined on single-crystal X-ray data (Mo K α radiation) to R 1 = 0.047. Cairncrossite belongs to the gyrolite and reyerite mineral groups, it is characterized by sheets consisting of edge-sharing CaO 6 octahedra, which are corner-linked on both sides to silicate layers. These units are intercalated by layers formed by SrO 8 polyhedra, which are arranged in pairs via a common edge, and further bound to disordered NaO 6 polyhedra. A complex system of hydrogen bonds strengthens the linkage to adjacent silicate layers. Cairncrossite exhibits a two-phase endothermic weight loss of the H 2 O molecules in the range 25–400°C; however, the mineral shows a nearly complete rehydration capability up to 400°C. The new mineral is named in honour of Bruce Cairncross, Professor and Head of the Department of Geology, University of Johannesburg.

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: 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.