Lopatkaite, ideally Pb10As2Sb6S22 (Z=4), is a new arsenic-bearing sulfosalt found in the Madoc deposit, Taylor Pit, Ontario, Canada. Associated minerals in the holotype specimen are boulangerite, veenite, and sterryite, all embedded in a calcite matrix. Lopatkaite is greyish black and opaque, with metallic lustre and dark-grey streak. It is brittle without any discernible cleavage and parting and has a Mohs hardness of 3-3.5. In reflected light lopatkaite is greyish white, with distinct bireflectance and pleochroism from white to grey, especially in oil. Under crossed polarisers, anisotropism is distinct, with rotation tints in shades of grey. Reflectance measurements in air yield the following Rmin/Rmax values based on the standard wavelengths (Commission on Ore Mineralogy, COM): 37.0 % / 39.3 % (470 nm), 34.1 % / 36.9 % (546 nm), 33.1 % / 36.2 % (589 nm), and 31.3 % / 34.1 % at (650 nm). The average result of four electron probe microanalyses for the structurally investigated grain is as follows (in wt %): Pb 57.81(4), As 3.53(8), Sb 20.03(6), S 19.08(6), and total 100.46(22), corresponding to Pb10.28(3)As1.74(4)Sb6.06(3)S21.92(3) (based on 18Me + 22S = 40 atoms per asymmetric unit). The density calculated using the empirical formula is 6.168 Mg m-3. Single-crystal X-ray diffraction data show lopatkaite to be monoclinic, space group P21/c (no. 14), with a=8.0806(6), b=23.3597(18), c=21.4880(16) & Aring;, beta=100.7090(10)degrees, V=3985.4(5) & Aring;3, and Z=4. The seven strongest lines in the (calculated) powder diffraction pattern are as follows (d in & Aring; (intensity) (hkl)): 3.728(39) 211, 3.712(100) 035, 3.653(35) 062, 2.804(41) -261, 2.780(43) 260, 2.779(38) -262, and 2.020(47) -402. The ideal formula is in accordance with the results of the crystal structure analysis, Pb10.336As1.567Sb6.088S22 , and may be derived from the ideal boulangerite formula, Pb10Sb8S22 (Z=4), by means of substitution of two Sb atoms with two As atoms. Lopatkaite is an isotype of boulangerite, differing by dominant As occupancy at two crystallographically independent mixed (Sb, As) sites. This dominant-site substitution defines lopatkaite as the arsenic-dominant isotype of boulangerite and justifies its recognition as a distinct mineral species. Lopatkaite is also a new member of the rod-based family of sulfosalts.

Abstract. Spaltiite is a new thallium sulfosalt with the ideal formula of Tl2Cu2As2S5. It was found on a dump of the famous mineral locality Lengenbach (Binntal, Canton Valais, Switzerland). A small piece of pure white Triassic dolomite belonging to the Penninic Monte Leone Nappe hosts three euhedral long prismatic to lath-like spaltiite crystals, each approximately 2 mm in length but only ∼0.2 mm thin. The hand specimen contains small quantities of pyrite, drechslerite and hatchite. The spaltiite crystals are greyish to black in colour and extremely soft. The Mohs' hardness is 1.5–2 (VHN15 ranges from 30 to 65, mean 47 kg mm−2). The mono-clinic crystals have a perfect cleavage parallel to {100}, which produces minute and plastic slabs. Reflectance measurements in air yield the following Rmin/Rmax values based on the standard wavelengths (Commission on Ore Mineralogy, COM): 27.0 % / 32.6 % (470 nm); 26.8 % / 32.1 % (546 nm); 26.0 % / 31.1 % (589 nm); and 24.8 % / 29.3 % (650 nm). Averaged electron-microprobe analyses (n=10) gave (in wt %) Tl 47.41(19), Cu 15.46(12), Ag 0.15(6), As 17.36(14), Sb 0.41(5) and S 19.20(8), total 99.99(32). The empirical formula is Tl1.94Cu2.04Ag0.01As1.95Sb0.03S5.03, calculated based on 11 apfu. The large crystals exhibit a remarkably homogeneous composition. Spaltiite crystallises in space group P21/c (a=15.791(8), b=10.000(5), c=6.323(3) Å, β=99.25(8)°, V=985.5(8) Å3). The crystal structure was determined from single-crystal X-ray diffraction data (R1=12.18 % for 4753 data, with Fo>4σ (Fo) and 101 variable parameters). Spaltiite exhibits a pronounced layered atomic arrangement: two polar Cu–As layers in (1/4 y z) and (3/4 y z), respectively, are related by inversion symmetry. Sandwiched between them are the Tl atoms. These two layers are centred in (0 y z) and (1/2 y z), centrosymmetric but topologically and crystallographically distinct. The eight strongest intensities in the X-ray powder diagram are [d in Å (intensity) hkl]: 3.914 (40) 021; 2.988 (63) 510; 3.496 (45) 311; 2.869 (45) 5‾11; 2.652 (36) 3‾31; 3.646 (34) 2‾21; 2.506 (29) 040; 2.762 (26) 202. The name of the new mineral originates from the nickname “spalti”, which was used during laboratory studies, illustrating the extremely pronounced cleavage (in German, “spalten” means cleave).

The crystal structure of Na2Mg(SO4)2 has been redetermined from X-ray diffraction on a larger, higher-quality synthetic single crystal than that used for the original determination. This allowed the correction of important details of the crystal structure. The substitution of equal amounts of Mg and Na has been shown to occur at sites different from those previously believed to be involved. It explains the large, unusually anisotropic atomic displacement parameters (ADPs) and the splitting of many O sites as adjustments to the significantly different sizes of Mg and Na atoms that enter the same coordination environment. An orientation disorder at one S site has been identified and explained; likewise, splitting of a nearby Na site and its exceptionally large, anisotropic ADPs are due to movement within a large structural cavity within the [100] structural channel. The complex crystal structure contains [MgO6] octahedral coordinations, of which one has partial Mg/Na occupancy, with six [SO4] tetrahedral coordinations attached in a pinwheel arrangement. An exception is one Mg octahedron that shares an edge with an S tetrahedron. The Mg-S coordination units are assembled in three-layer (101) slabs, interconnected by additional Mg in octahedral coordination. Na atoms are located in voids within this framework, with coordination numbers ranging from 5 to 9.

The new mineral argentopearceite (IMA2020-049) was found at the mine dump of the abandoned Lehnschafter mine, Mikulov-Hrob district (holotype), and later at museum samples (cotypes) from the Moldava fluorite deposit, both in the Kru & scaron;n & eacute; hory Mountains, Czech Republic. Argentopearceite is associated with proustite in quartz gangue (Mikulov) or acanthite and proustite in fluorite gangue (Moldava). The new mineral occurs as tabular (pseudo)hexagonal crystals up to 0.8 mm (Mikulov) and 3 mm (Moldava), and as groups and aggregates up to 1 cm. Argentopearceite from Mikulov is steel grey to black. Mohs hardness is ca. 3; the calculated density is 6.29 g.cm(-3). In reflected light, argentopearceite is grey with a greenish shade. Bireflectance was not observed and pleochroism is very weak. Anisotropy under crossed polars is moderate with weak greenish and green-blue tints. Internal reflections were not observed. Reflectance values of argentopearceite in air (R-min/R-max, %) are: 27.3/30.0 at 470 nm, 26.6/29.3 at 546 nm, 26.2/28.8 at 589 nm, and 25.9/28.1 at 650 nm). The empirical formula for argentopearceite, based on electron-microprobe analyses (n = 15), is (Ag15.95Cd0.02)(Sigma 15.97)(As1.82Sb0.11)(Sigma 1.93)(S11.03Cl0.05Te0.01)(Sigma 11.09). The ideal formula is Ag16As2S11, which requires (in wt.%) Ag 77.45, As 6.72 and S 15.83, total of 100.00. Argentopearceite is trigonal, P321, a = 14.8583(5), c = 12.3038(15) & Aring;, with V = 2352.38(15) & Aring;(3) and Z = 4. Its crystal structure was refined by single-crystal X-ray diffraction data to a final R-1 = 0.0773 on the basis of 6594 unique reflections with F-o > 3 sigma(F) and 242 refined parameters. The structure of argentopearceite mostly conforms to the general architecture of the As-dominant members of the pearceite-polybasite family of minerals.

Erzwiesite, ideally Ag8Pb12Bi16S40, Z= 1, is a new sulfosalt mineral discovered in the Erzwies mining area, Gastein Valley, Salzburg Province, Austria. The mineral occurs as small black, irregular needle-like crystals mixed with galena and heyrovsk & yacute;ite in a quartz matrix. In reflected light, erzwiesite is greyish white. Under crossed polars it is distinctly anisotropic, and the rotation tints change from pale brown to pale bluish grey to dark brown. Reflectance measurements in air yield the following R-min/R-max values based on the standard wavelengths (Commission on Ore Mineralogy, COM): 44.5/47.6 (470 nm), 41.9/45.0 (546 nm), 41.5/44.5 (589 nm), and 40.4/43.6 (650 nm). The Mohs' hardness is 3-3.5 (VHN50 ranges from 195 to 224, mean 210 kg mm(-2)). Averaged electron-microprobe analyses (n= 6) gave (in wt %) Ag 11.10(27), Cu 0.04(3), Pb 29.50(77), Cd 0.17(1), Bi 42.90(63), Te 0.21(14), Se 0.08(5), and S 16.08(11), with a total of 100.10(63). The empirical formula is Ag8.18Cu0.05Pb11.31Cd0.12Bi16.30Sb0.01S39.81Te0.13Se0.06 (based on 76 apfu). The calculated density is 7.075 g cm(-3) using the empirical formula. Erzwiesite crystallises in space group Cmcm (a= 4.085(5), b= 13.462(15), c= 33.92(4) & Aring;, and V= 1866(4) & Aring;3). The crystal structure was determined from single-crystal X-ray diffraction data (R-1= 5.24 % for 308 data with F-o > 4 sigma(F-o) and 51 variable parameters). The structural formula is Ag8.64Pb11.04Bi16.32S40. The seven strongest lines in the X-ray powder diagram are [d in & Aring; (intensity) hkl] 3.588 (64) 028, 3.387 (98) 115, 3.349 (37) 041, 3.288 (85) 029, 2.919 (100)133, 2.846 (99)134, and 2.039(43) 157. Erzwiesite is the first natural (8 : 8) homologue of the lillianite homologous series and is named after its type locality.

The crystal structure of l & ouml;weite, Na12Mg7(SO4)(1)(3)(H2O)(1)(5), has been redetermined using single-crystal X-ray diffraction on a synthetic crystal to resolve ambiguities present in the original structure reported by Fang and Robinson (1970). The new data were collected with a modern charge-coupled device (CCD)-equipped diffractometer and refined anisotropically. The resulting structure has a trigonal unit cell [space group R\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\:\overline3$$\end{document}, a = 18.8483(5) & Aring;, c = 13.4190(4) & Aring;, Z = 3, R1 = 0.0269, Rw=0.0345]. It confirms previous results while revealing new details, including anisotropically refined oxygen positions with resolved overlaps and most hydrogen positions. Hydrogen atom positions were determined for the two symmetry-independent water molecules' sites, while they remain unclear for the third one. This redetermination provides a more accurate model of the coordination environments of Mg and Na atoms. It clarifies the features of the hydration and bonding in l & ouml;weite, with a more detailed description of its crystal structure. It is built on a three-dimensional framework with the composition Na12Mg6(SO4)12(H2O)12 in which hydrogen bonding plays a minor role. This part of the structure conforms with the general chemistry of the Na-Mg sulfate hydrate series and explains the high thermal stability of l & ouml;weite. The framework contains channels where additional Mg atoms, sulphate groups, and water molecules are situated. This part of the structure contributes to an unusually low Na:Mg ratio, compared to other hydrated Na-Mg sulfates. The channel water molecules exhibit large, anharmonic displacements, possibly due to a combination of bonding to framework Na atoms and hydrogen bonding to an oxygen atom of the channel sulphate group.

Spaltiite is a new thallium sulfosalt with the ideal formula of Tl2Cu2As2S5. It was found on a dump of the famous mineral locality Lengenbach (Binntal, Canton Valais, Switzerland). A small piece of pure white Triassic dolomite belonging to the Penninic Monte Leone Nappe hosts three euhedral long prismatic to lath-like spaltiite crystals, each approximately 2 mm in length but only similar to 0.2 mm thin. The hand specimen contains small quantities of pyrite, drechslerite and hatchite. The spaltiite crystals are greyish to black in colour and extremely soft. The Mohs' hardness is 1.5-2 (VHN15 ranges from 30 to 65, mean 47 kg mm(-2)). The mono-clinic crystals have a perfect cleavage parallel to {100}, which produces minute and plastic slabs. Reflectance measurements in air yield the following R-min/R-max values based on the standard wavelengths (Commission on Ore Mineralogy, COM): 27.0 % / 32.6 % (470 nm); 26.8 % / 32.1 % (546 nm); 26.0 % / 31.1 % (589 nm); and 24.8 % / 29.3 % (650 nm). Averaged electron-microprobe analyses (n=10) gave (in wt %) Tl 47.41(19), Cu 15.46(12), Ag 0.15(6), As 17.36(14), Sb 0.41(5) and S 19.20(8), total 99.99(32). The empirical formula is Tl1.94Cu2.04Ag0.01As1.95Sb0.03S5.03, calculated based on 11 apfu. The large crystals exhibit a remarkably homogeneous composition. Spaltiite crystallises in space group P2(1/c) (a=15.791(8), b=10.000(5), c=6.323(3) & Aring;, beta=99.25(8)degrees, V=985.5(8) & Aring;(3)). The crystal structure was determined from single-crystal X-ray diffraction data (R-1=12.18 % for 4753 data, with F-o>4 sigma (F-o) and 101 variable parameters). Spaltiite exhibits a pronounced layered atomic arrangement: two polar Cu-As layers in (1/4 yz) and (3/4 yz), respectively, are related by inversion symmetry. Sandwiched between them are the Tl atoms. These two layers are centred in (0 yz) and (1/2 yz), centrosymmetric but topologically and crystallographically distinct. The eight strongest intensities in the X-ray powder diagram are [d in & Aring; (intensity) hkl]: 3.914 (40) 021; 2.988 (63) 510; 3.496 (45) 311; 2.869 (45) 5 & oline;11; 2.652 (36) 3 & oline;31; 3.646 (34) 2 & oline;21; 2.506 (29) 040; 2.762 (26) 202. The name of the new mineral originates from the nickname "spalti", which was used during laboratory studies, illustrating the extremely pronounced cleavage (in German, "spalten" means cleave).

The new minerals auropolybasite, ideally Ag15AuSb2S11, and auropearceite, ideally Ag15AuAs2S11, were found at the & Scaron;ibeni & ccaron;n & yacute; vrch near Nov & aacute; Ba & ncaron;a in Slovakia. They were found as anhedral grains up to 0.2 mm in size, usually rimmed by acanthite. Both new minerals are associated with acanthite, argentopolybasite, argentopearceite, pyrargyrite, proustite, stephanite, selenostephanite, rozhdestvenskayaite-(Zn), zv & ecaron;stovite-(Zn), zv & ecaron;stovite-(Fe), naumannite, Au-Ag alloys, uytenbogaardtite, iodargyrite, and bromargyrite. They are dark grey to black, opaque, with a black streak and metallic luster. The Mohs hardness is similar to 3. They are brittle with no observable cleavage and with a conchoidal fracture. The calculated densities are 6.622 g/cm3 for auropolybasite and 6.606 g/cm3 for auropearceite. In reflected light, auropolybasite and auropearceite are gray with a bluish tint, no observable bireflectance, and very weak pleochroism. They show moderate anisotropy in crossed polars with weak greenish and green-blue tints. The reflectance values for wavelengths recommended by the Commission on Ore Mineralogy of the IMA are (Rmin/Rmax, %): 33.5/31.6 (470 nm), 32.9/31.1 (546 nm), 32.1/30.6 (589 nm), and 30.2/29.3 (650 nm) for auropolybasite and 30.6/29.8 (470 nm), 30.3/29.2 (546 nm), 29.7/28.7 (589 nm), and 28.1/27.4 (650 nm) for auropearceite. The empirical formula (based on 29 apfu) for auropolybasite is Ag15.27Au0.84(Sb1.51As0.46)Sigma 1.97(S10.55Se0.30Cl0.06)Sigma 10.91 and that for auropearceite is Ag15.84Au0.88 (As1.33Sb0.44)Sigma 1.76(S10.46Se0.05Te0.01)Sigma 10.52. The ideal end-member formulas are Ag15AuSb2S11 for auropolybasite and Ag15AuAs2S11 for auropearceite. Their symmetry is trigonal, space group P321. Latice parameters for auropolybasite are: a = 15.1091(5) & Aring;, c = 12.1518(5) & Aring;, V = 2402.42(15) & Aring;3, Z = 4, and those for auropearceite are: a = 14.995(3) & Aring;, c = 12.115(2) & Aring;, V = 2359.3(8) & Aring;3, Z = 4. Crystal-structure analysis of auropolybasite confirmed that its atomic arrangement is isotypic to that of the other members of the polybasite group and it is isostructural with auropearceite. These minerals formed in the waning stages of epithermal systems, where reduced, S-rich, low-salinity fluids transported Au, Ag, Sb, and As as thiocomplexes. These fluids were unable to transport Cu, Pb, and Zn, thus explaining the chemical composition of these minerals and the entire mineral assemblage.

The crystal structure of löweite, Na₁₂Mg₇(SO₄)₁₃(H₂O)₁₅, has been redetermined using single-crystal X-ray diffraction on a synthetic crystal to resolve ambiguities present in the original structure reported by Fang and Robinson (1970). The new data were collected with a modern charge-coupled device (CCD)-equipped diffractometer and refined anisotropically. The resulting structure has a trigonal unit cell [space group R 3 , a = 18.8483(5) Å, c = 13.4190(4) Å, Z = 3, R1 = 0.0269, Rw=0.0345]. It confirms previous results while revealing new details, including anisotropically refined oxygen positions with resolved overlaps and most hydrogen positions. Hydrogen atom positions were determined for the two symmetry-independent water molecules’ sites, while they remain unclear for the third one. This redetermination provides a more accurate model of the coordination environments of Mg and Na atoms. It clarifies the features of the hydration and bonding in löweite, with a more detailed description of its crystal structure. It is built on a three-dimensional framework with the composition Na12Mg6(SO4)12(H2O)12 in which hydrogen bonding plays a minor role. This part of the structure conforms with the general chemistry of the Na-Mg sulfate hydrate series and explains the high thermal stability of löweite. The framework contains channels where additional Mg atoms, sulphate groups, and water molecules are situated. This part of the structure contributes to an unusually low Na:Mg ratio, compared to other hydrated Na-Mg sulfates. The channel water molecules exhibit large, anharmonic displacements, possibly due to a combination of bonding to framework Na atoms and hydrogen bonding to an oxygen atom of the channel sulphate group.

A rare silver mineral, dervillite (ideally Ag2AsS2), has been found in specimens from the famous Jachymov mining district, Czech Republic. It occurs as very rare long-prismatic crystals up to 0.4 mm across in association with proustite, bismuth and native silver in the thin arsenic veinlets within the Trojicka vein (Svornost mine). Dervillite is monoclinic, space group Pc, with a = 9.6375(3), b = 12.9462(4), c = 6.8497(2) & Aring;, beta = 99.510(2)degrees and V = 842.88(2) & Aring;(3) (Z = 8). The new structure refinement, R-1 = 2.94% for 18767 reflections with [I > 3 sigma(I)] and wR(2) = 7.93% for all 20050 reflections, provided a better fit to the data compared to earlier studies, revealing that silver (8 symmetrically independent atomic sites), which adopts various coordinations (from quasi-linear to tetrahedral) in the structure of dervillite vibrates non-harmonically at room temperature. The Gram-Charlier development, describing the atomic displacement parameters of silver atoms, was used to model their non-harmonic behaviour. A discussion on the use of the approach to the data with limited quality is also provided.

Selenodantopaite is a new mineral species discovered in a sample collected from the mine dumps of the abandoned Princ Ev & zcaron;en deposit near Pot & uring;& ccaron;ky, the Kru & scaron;n & eacute; hory Mts., Czech Republic. Selenodantopaite occurs as anhedral grains, up to 100 mu m in size, in a quartz gangue with abundant coffinitized uraninite, chalcopyrite and pyrite; it is also associated with bohdanowiczite, unnamed selenide (Bi,Ag)3(Se,S,Te)4, minerals of the galena-clausthalite solid solution, sphalerite and tennantite-(Fe). Selenodantopaite is dark grey, with metallic lustre. Mohs hardness is ca. similar to 3 & half;, calculated density is 7.403 g.cm-3. In reflected light, selenodantopaite is white to light grey; bireflectance and pleochroism are weak, anisotropy is distinct with light bluish white - light purplish brown rotation tints. Internal reflections were not observed. Reflectance values for the four COM wavelengths of selenodantopaite in air [Rmax, Rmin (%) (lambda in nm)] are: 48.3, 44.9 (470); 48.8, 45.3 (546); 48.4, 45.1 (589); and 47.7, 44.6 (650). The empirical formulae, based on electron-microprobe analyses, are Cu0.24(4)Ag5.09(7)Fe0.17(5)Pb0.51(4)Bi12.32(21)Se15.11(21)S6.89(21) and Cu0.05(3)Ag5.23(11)Fe0.06(4)Pb0.62(12)Bi12.38(13)Se14.77(16)S7.23(16) for Cu-bearing and Cu-poor variety, respectively. The ideal formula is Ag5Bi13Se22 (Z = 1), which requires (in wt.%) Ag 10.80, Bi 54.41, and Se 34.79, total 100.00. Selenodantopaite is monoclinic, C2/m, with unit-cell parameters a = 13.670(4), b = 4.1400(11), c = 19.282(6) & Aring;, beta = 106.385(11)degrees and V = 1046.9(5) & Aring;3. According to the single-crystal X-ray diffraction data (R1 = 0.0625), the crystal structure of selenodantopaite is isotypic with that of dantopaite and it is composed by two kinds of slabs, parallel to (001), i.e. a PbS-like thick slab and a thin slab, following the classical structural scheme of pavonite homologues. Selenodantopaite is named in accord with its composition and its relationship with dantopaite. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (2023-092)

AbstractThe new mineral argentopolybasite, ideally Ag16Sb2S11, was found at the Kremnica Au–Ag epithermal deposit, Žiar nad Hronom Co., Banská Bystrica Region, Slovakia (type locality), Šibeničný vrch near Nová Baňa, Žarnovica Co., Banská Bystrica Region, Slovakia (cotype locality) and the Arykevaam epithermal Au–Ag deposit, Anadyr’ District, Chukotka Autonomous Okrug, Russian Federation (cotype locality). At the Kremnica deposit argentopolybasite was found as discrete, well-developed (pseudo)hexagonal tabular crystals up to 4 mm in size or as complex crystalline aggregates and groups up to 5 mm in size in cavities of quartz. It is associated with pyrargyrite, polybasite, stephanite, miargyrite, rozhdestvenskayaite-(Zn), argentotetrahedrite-(Zn), naumannite, gold and pyrite. Argentopolybasite is dark grey to black, with a black streak and metallic to opaque lustre. The Mohs hardness is ~3. It is brittle with no observable cleavage and with a conchoidal fracture. The calculated density is 6.403 g⋅cm–3. In reflected light, argentopolybasite is grey, with no observable bireflectance and very weak pleochroism. It shows moderate anisotropy in crossed polarisers with weak greenish and green–blue tints. The reflectance values for wavelengths recommended by the Commission on Ore Mineralogy of the IMA are (Rmin/Rmax, %): 30.3/31.0 (470 nm), 28.8/29.3 (546 nm), 28.1/28.6 (589 nm) and 27.4/27.8 (650 nm). The empirical formulae (based on 29 apfu) are, Kremnica: (Ag15.94Cu0.18)Σ16.12(Sb1.40As0.61)Σ2.01(S10.60Se0.25Cl0.03)Σ10.88, Nová Baňa: Ag16.30(Sb1.74As0.22)Σ1.96(S10.69Cl0.04)Σ10.73and Arykevaam: (Ag15.54Cu0.38)Σ15.92(Sb1.56As0.51)Σ2.07S11.01. The ideal end-member formula for argentopolybasite is Ag16Sb2S11. Argentopolybasite is trigonal, space groupP321,a= 15.0646(5) Å,c= 12.2552(5) Å,V= 2408.61(15) Å3andZ= 2. The seven strongest powder X-ray diffraction lines are [dobsin Å, (I),hkl]: 12.169, (40), 001; 3.162, (100), 041; 3.045, (54), 004; 2.881, (45), 042; and 2.4256, (28), 421. The crystal structure of argentopolybasite from Kremnica, refined toRobs= 0.0741 for 2804 observed reflections, confirmed that the atomic arrangement is isotypic to that of the other members of the polybasite group and it is isostructural with argentopearceite.

Ornamental adornment of the Kharraqan tomb towers, the most outstanding funeral monuments of the Seljuk era in NW Iran, and those of four best-preserved Seljuq brick minarets in northern Iran, documents the artistic canon of the pre-glaze stage of Iranian Islamic architecture. Despite some later interruptions, these monuments and their plain-brick ornaments, as well as the ‘virtually interlaced’ brick ornaments, stand at the beginnings of a rich development that led to the Safavid architecture of Iran. Besides documentation and study of the geometric character of early Islamic art, which was based on limited technical resources, this study offers insight into symmetry concepts developed at this stage of art and architecture development. This is the last and most complete study of the Kharraqan towers performed before their overwhelming destruction in the 2002 earthquake.

Quasiperiodic ornamental patterns represent only a small percentage of patterns when compared to the entire body of periodic patterns. Decagonal pattern is known since twelfth century Iran and fourteenth century western Islam (Andalusia and Morocco). A rich spectrum of octagonal patterns exists at the latter localities (fourteenth century and later), whereas a sole example of a dodecagonal pattern comes from Morocco. Later copies exist in all these regions. My most recent studies were concentrated upon the Andalusian and Moroccan regions, in which the fourteenth century (and later) wall mosaics occur as uninterrupted coatings of entire walls so that the motif of individual panels had to be adjusted to secure continuity of their underlying bar-and-band structure. In Andalusia, the tetragonal structure of the panels and their complexes were locally adjusted to become octagonal quasiperiodic. Only two geometric types of such octagrids were derived in Andalusia, in agreement with the rarity of quasiperiodic ornaments in general. In Morocco, before the panel substructure became heavily masked by an overflow of rosettes of several sizes, the mosaic panel was based on an octagonal quasiperiodic grid and ornamental rosettes were placed in it, disposed in the form of concentric octagons. As a prominent example, the octagonal motif of the Nejjarine Fountain and its plaster encasement will be discussed.

Mineralogical Society of the UK and IrelandDuring the time when we had to pivot to online-only communications, we found new ways to communicate and new things to communicate about.Some of these continue to be developed and enhanced and will be with us into the future, I believe.Over the past couple of years, the Society has invested heavily in online material, released in support of the community during a challenging time.This included recorded seminars, training material, Public Understanding of Science information, interviews with mineralogists, and much more.For example, go to https://www.youtube.com/

Famous representational and religious bronze vessels of the blossoming Chinese Bronze Age (about 2200 - 700 BC) were made by casting molten bronze into molds composed of several ornamental panels. The latter were prepared with abstract design based on highly schematized animal face (taotie), sometimes with schematic dragon bodies added, and consisting of several orders of hook-to-full spiral elements. The largest, 1st order elements are often covered by arrays of smaller, 2nd order elements, and larger arrays of these, by 3rd order arrays. Linear and/or branched arrays of 3rd order spirals cover spaces and fields between higher order elements, as well. The three-tier design, with a semiregular distribution of different orders dictated by a compromise between the rules of abstraction and zoomorphism, unity of principles over three orders of importance, as well as maintenance of inclusivity condition, and statistical self-similarity of the design, imparts to the Chinese Bronze Age art a fractal character. This character has been preserved and even further intensified over a considerable time span.

Kobellite is a Pb-Bi-Sb sulfosalt with minor amounts of (Cu, Fe) and with the crystal structure composed of two types of rods, one of which has unusual lateral extensions (‘lobes’), which depart from the usual lozenge-shaped rod cross-section in sulfosalts. Several Pb-Bi-Sb and Pb-Sb-rich sulfosalts form a small group built on similar principles. Some of them are related by homology (e.g., izoklakeite), and differ by the perpendicular dimensions of rods (length and multiplicity of atomic layers in a rod; e.g., sterryite), and especially by different combinations of archetypes and archetype portions which participate in the rods (PbS archetype and the two orientations of SnS archetype). The present article summarizes and discusses the published data on the group. Homeotypism makes the group interesting and potentially a fertile source of further structural varieties.

ABSTRACT Stibiogoldfieldite, Cu12(Sb2Te2)S13, was approved as a new mineral species from the Mohawk mine, Goldfield mining district, Esmeralda County, Nevada, USA. It occurs as metallic anhedral grains, dark grey in colour. It is associated with quartz, pyrite and an Ag–Bi–(S,Se) phase (holotype material) and with quartz, pyrite, calaverite, bismuthinite, bohdanowiczite, and the Ag–Bi–(S,Se) phase (cotype material). In reflected light, stibiogoldfieldite is isotropic, grey in colour, with indistinct brownish shade. Reflectance data in air [R (%)] are: 31.1 at 470 nm, 30.9 at 546 nm, 30.8 at 589 nm and 31.0 at 650 nm. Electron microprobe analysis for holotype material gave (in wt.% – average of 60 spot analyses): Cu 45.03(60), Ag 0.26(7), Fe 0.02(3), Zn 0.13(15), Sn 0.02(4), Pb 0.05(6), Sb 8.02(62), As 2.80(65), Bi 2.77(87), Te 15.15(1.24), S 24.50(32), Se 0.52(11), total 99.27(69). On the basis of (As + Sb + Te + Bi) = 4 atoms per formula unit (apfu), the empirical formula of stibiogoldfieldite is (Cu12.05Ag0.04Zn0.03Fe0.01)Σ12.13(Sb1.12As0.63Bi0.23Te2.02)Σ4.00(S12.99Se0.11)Σ13.10. Chemical data on an additional sample from the same locality (cotype material) gave the following results (in wt.% – average of 181 spot analyses): Cu 43.84(63), Ag 0.21(7), Sb 5.92(78), As 2.63(45), Te 20.07(1.19), S 25.13(53), Se 0.97(35), total 99.47(66). On the basis of (As + Sb + Te + Bi) = 4 apfu, the empirical formula of cotype material is (Cu11.30Ag0.03)Σ11.33(Sb0.80As0.57Bi0.06Te2.57)Σ4.00(S12.83Se0.20)Σ13.03. Stibiogoldfieldite is cubic, I$\overline 4$3m, with unit-cell parameters a = 10.3466(17) Å, V = 1107.6(5) Å3 and Z = 2 (holotype). Unit-cell parameters for the cotype sample are a = 10.3035(2) Å and V = 1093.83(7) Å3. The crystal structure of holotype stibiogoldfieldite was refined by single-crystal X-ray diffraction data to a final R1 = 0.032 on the basis of 285 reflections with Fo > 4σ(Fo) and 20 refined parameters. Stibiogoldfieldite is isotypic with other members of the tetrahedrite group.

Stibioastalecite, Cu-12(Sb2Te2)Se-13, was approved as a new mineral species from the Ustalec mine, 15 km west of Horaz'ovice, SW Bohemia, Czech Republic. It occurs as metallic anhedral grains up to 0.1-0.3 mm in size, dark grey in color, in a calcite gangue. It is directly associated with hakite-(Hg), berzelianite, the not-yet approved phase Cu-12(As2Te2) Se-13 and uraninite. Stibioastalecite is brittle, with an indistinct cleavage and a conchoidal fracture; the calculated density is 5.676 g/cm(3). In reflected light, stibioastalecite is isotropic, and grey in color; internal reflections were not observed. Reflectance data for the four COM wavelengths in air are [lambda (nm): R (%)]: 470: 33.3; 546: 33.2; 589: 33.1; 650: 33.0. Electron microprobe analysis for holotype material (grain used for single-crystal X-ray study) gave (in wt. % - average of 7 spot analyses): Cu 34.10, Ag 1.22, Fe 0.04, Zn 0.09, Hg 0.33, Sb 9.39, As 0.70, Te 12.41, S 3.76, Se 37.59, total 99.63. On the basis of (As + Sb + Te) = 4 atoms per formula unit (apfu), the empirical formula of stibioastalecite is (M(2))(Cu5.75Ag0.25)(Sigma 6)(M(1))(Cu5.93Hg0.04Zn0.03Fe0.02)(Sigma 6.02)(X(3))(Te2.12Sb1.68As0.20)(Sigma 4)(Se10.36S2.55)(Sigma 12.91). The ideal formula is Cu6Cu6(Sb2Te2)Se-13, which requires Cu 33.33, Sb 10.64 Te 11.16 Se 44.87, total 100 wt. %. Stibioastalecite is cubic, I (4) over bar 3m, with unit-cell parameters a = 10.828(4) angstrom, V = 1269.6(9) angstrom(3), Z = 2. The crystal structure of stibioastalecite was studied by single-crystal X-ray diffraction data and it is isotypic with other members of the tetrahedrite group. The mineral is named after its type locality Ustalec and its chemical composition, being the (Sb/Te) end-member in the possible astalecite series.