A world-unique association of staročeskéite, izoklakeite and terywallaceite from Kutná Hora ore district, Czech Republic

The new mineral radvaniceite, GeS2, was found on the burning coal mine dump of the abandoned Kateřina coal mine at Radvanice, near Trutnov, northern Bohemia, Czech Republic. It occurs as aggregates resembling cotton tufts up to 5 mm in size; they are composed of acicular crystals up to fibres about 1–5 μm thick and up to 3 mm in length. Individual fibres are distorted and partly resemble bent wires nucleated on rock fragments or on black, crumbly ash, in association with minerals of solid solutions of Bi-Sb and stangersite, herzenbergite, and greenockite. Radvaniceite was also observed as irregular grains in a range of 10–50 μm in size, forming part of earlier multicomponent aggregates upon which the above-described crystals grow. These aggregates are formed, in addition to radvaniceite, by minerals of Bi-Sb, Bi2S3-Sb2S3 and Bi2S3-Bi2Se3 solid solutions, Bi3S2, Bi-sulpho/seleno/tellurides, tellurium, unnamed PbGeS3, Cd4GeS6, GeAsS, Sn5Sb3S7, stangersite, greenockite, cadmoindite, herzenbergite, teallite, and Sn- and/or Se-bearing galena. Radvaniceite is formed under reducing conditions by direct crystallization from hot gasses (250–350 °C) containing Cl and F at a depth of 30–60 cm under the surface of a burning coal mine dump; the mine dump fire started spontaneously, and no anthropogenic material was deposited there. Acicular crystals up to fibres of radvaniceite are elastic to flexible; are white to yellowish grey in colour, with white streaks; are translucent in transmitted light; and have vitreous to adamantine lustre. Cleavage and fracture were not observed. The calculated density is 3.05 and 2.99 g·cm−3 for the empirical and ideal formulae, respectively. Radvaniceite is transparent under the microscope, with a very weak pleochroism (from colourless to pale greenish yellow), and has a refraction index > 1.8. Under reflected light, radvaniceite is light grey; bireflectance and pleochroism were not observed due to abundant, white to grey, internal reflections. Anisotropy in crossed polars is distinct with grey rotation tints. Reflectance values of radvaniceite in air (Rmin–Rmax, %) are: 15.4–18.8 at 470 nm, 16.1–20.4 at 546 nm, 16.4–20.8 at 589 nm, and 16.9–20.9 at 650 nm. The empirical formula, based on electron-microprobe analyses, is (Ge0.99Bi0.01)Σ1.00(S1.97Se0.03)Σ2.00. The ideal formula is GeS2, which requires Ge 53.10, S 46.90, total 100 wt. %. Radvaniceite is monoclinic, Pc, a = 6.8831(12), b = 22.501(3), c = 6.8081(11) Å, β = 120.365(9)°, with V = 909.8(4) Å3 and Z = 12. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I) (hkl)] are: 5.7395 (100) (11-1, 110), 5.2067 (16) (021), 3.3650 (33) (111, 11-2), 2.8417 (33) (022), 2.8236 (16) (170, 17-1), 2.8134 (20) (080) and 2.6257 (19) (240, 24-2). According to X-ray powder diffraction data and Raman spectroscopy, radvaniceite is a natural analogue of synthetic monoclinic low-temperature β-GeS2 with distorted GeS4 tetrahedra forming four corner-sharing tetrahedral chains, which are connected by corner-sharing tetrahedra in a three-dimensional structure. We named the mineral after its type locality, Radvanice, one of the past centres of coal mining in the Czech limb of the Intra-Sudetic Basin. This mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (number 2021-052).

AbstractŠkáchaite (IMA2022–143) is a new mineral species discovered in samples from the hydrothermal vein B117, shaft No. 6 at the Brod deposit of the uranium and base-metal Příbram ore district, central Bohemia, Czech Republic. Škáchaite is a Co-dominant member of the dolomite group and forms anhedral grains up to 50 μm in size and as 20–100 μm thick growth zones in škáchaite–dolomite crystals as a part of carbonate (dolomite, calcite, siderite, spherocobaltite, ankerite, kutnohorite and minrecordite) gangue, associated with native silver, sulfides and arsenides. Škáchaite is pale to bright pink with vitreous lustre. The Mohs hardness is ca. 3½–4, similar to other members of the dolomite group. The calculated density is 3.140 g.cm–3. Škáchaite is optically uniaxial (–); the indices of refraction are ω = 1.741(3) and ɛ = 1.535(3). On the basis of electron-microprobe analyses, its empirical formula is Ca1.00(Co0.45Mg0.38Ca0.08Fe0.05Mn0.03Zn0.01)Σ1.00(CO3)2. The ideal formula is CaCo(CO3)2, which requires (in wt.%) CaO 25.60, CoO 34.21, CO2 40.19, a total of 100.00. Škáchaite is trigonal, R$\bar{3}$, with unit-cell parameters a = 4.8177(18), c = 16.093(7) Å, V = 323.5(2) Å3 and Z = 3. The strongest reflections of the calculated powder X-ray diffraction pattern [d, Å, (Irel, %) hkl] are: 3.704 (13) 10$\bar{2}$; 2.896 (100) 104; 2.409 (15) 110; 2.019 (17) 202; 1.812 (19) 10$\bar{8}$; and 1.792 (16) 11$\bar{6}$. According to the single-crystal X-ray diffraction data (R1 = 0.0304 for 94 reflections with [I > 3σ(I)]), the crystal structure of škáchaite is isotypic with its Mg-analogue, dolomite. The Raman spectrum of škáchaite, as well as the tentative assignment of observed bands, are given in this paper. The mineral is named in honour of Pavel Škácha, a Czech mineralogist and curator of the mineralogical collection of the Mining Museum Příbram, Czech Republic.

Selenodantopaite is a new mineral species discovered in a sample collected from the mine dumps of the abandoned Princ Evžen deposit near Potůčky, the Krušné hory Mts., Czech Republic. Selenodantopaite occurs as anhedral grains, up to 100 μm 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 . ∼3½, 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 [ R max , R min (%) (λ 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 Cu 0.24(4) Ag 5.09(7) Fe 0.17(5) Pb 0.51(4) Bi 12.32(21) Se 15.11(21) S 6.89(21) and Cu 0.05(3) Ag 5.23(11) Fe 0.06(4) Pb 0.62(12) Bi 12.38(13) Se 14.77(16) S 7.23(16) for Cu-bearing and Cu-poor variety, respectively. The ideal formula is Ag 5 Bi 13 Se 22 ( Z = 1), which requires (in wt.%) Ag 10.80, Bi 54.41, and Se 34.79, total 100.00. Selenodantopaite is monoclinic, C 2 /m , with unit-cell parameters a = 13.670(4), b = 4.1400(11), c = 19.282(6) Å, β = 106.385(11)° and V = 1046.9(5) Å 3 . According to the single-crystal X-ray diffraction data ( R 1 = 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)

The new mineral přibramite was found on the dump of shaft No. 16, one of the mines in the Přibram uranium and base-metal district, central Bohemia, Czech Republic. Přibramite is associated with antimonselite, permingeatite, dzharkenite, ferroselite, hakite, tetrahedrite, chameanite, giraudite, a new Hg-, Sb-, Cu selenide, a new Sb-, Cu selenide and uraninite in a calcite-dominant gangue. The new mineral occurs as columnar crystals up to 60 × 12 μm (in the section), growing together in aggregates up to 150 μm across in the calcite gangue. Přibramite crystals form intergrowths and replace older permingeatite; antimonselite crystals were observed in close association as well. Přibramite is brittle, is lead grey in colour, and has a metallic lustre. Mohs hardness is ca . 3–4; the calculated density is 5.884 g cm −3 . In reflected light přibramite is grey with a yellowish hue, bireflectance is medium, and pleochroism is weak with grey tints. Anisotropy is strong with grey to brownish rotation tints. Internal reflections were not observed. The empirical formula, based on electron-microprobe analyses, is Cu 1.00 (Sb 1.02 As 0.01 ) 1.03 (Se 1.81 S 0.15 ) 1.96 . The ideal formula is CuSbSe 2 , which requires Cu 18.52, Sb 35.47 and Se 46.01, total 100.00 wt%. Additional elements as Fe, Pb, Tl and Hg were found in small concentrations above detection limits. Přibramite is orthorhombic, Pnma , a = 6.3042(15), b = 3.980(1), c = 14.989(4) A, with V = 376.09(2) A 3 and Z = 4. The strongest reflections of the calculated powder X-ray diffraction pattern [ d , A (I)( h k l )] are: 3.152(40) (2 0 0), 3.113(100)(0 1 3), 3.085(40)(2 0 1), 3.395(63)(0 1 5), 1.9900(38)(0 2 0), 1.8442(42)(3 1 1) and 1.8329(33)(3 0 4). According to single-crystal X-ray diffraction data ( R obs = 0.0480), přibramite is unequivocally isostructural with chalcostibite and emplectite. The structure of přibramite contains one Cu, one Sb and two Se sites (last mentioned is occupied both by Se and S atoms). It is built up from square Sb pyramids linked to form chains of SbSe 2 along b and CuSe 4 tetrahedra forming chains of CuSe 3 parallel to b . These two types of infinite chains are then linked to form sheets that are stacked perpendicular to c . The effect of the larger Se atom, compared with S, is well reflected by the increased unit-cell volume of přibramite ( V přibramite ~ 380 A 3 ) compared with that of chalcostibite ( V chalcostibite ~ 330 A 3 ). Přibramite is named after the type locality, the Přibram uranium and base-metal district.

Abstract. 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) Å, β=100.7090(10)°, V=3985.4(5) Å3, and Z=4. The seven strongest lines in the (calculated) powder diffraction pattern are as follows (d in Å (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.

Julgoldite-(Fe 2+ ) and Fe-rich prehnite were found in pectolite veins filling fissures in basaltic andesite at the Kot'lov quarry near Semily (Liberec region, Czech Republic).Empirical formula of julgoldite-(Fe 2+ ) based on EPMA and Mssbauer spectroscopy considering so-called intervalence electron hopping in the structure may be written as Ca 2.01 (Fe 2+ 0.56 Fe 2.5+ 0.25 Mg 0.14 ) 0.95 (Fe 3+ 1.19 Fe 2.5+ 0.25 Al 0.57 ) 2.01 Si 3 O 9.94 (OH) 4.06 .Refined unit-cell parameters for monoclinic space group A2/m are a = 8.927(3) , b = 6.080(2), c = 19.428(7), = 97.59(4),V = 1045.2(8) 3 .Prehnite with the empirical formula Ca 2.01 (Al 0.53 Fe 0.45 ) 0.98 (AlSi 3 O 10 )(OH) 1.93 F 0.02 is located approximately in the middle of the prehnite-ferriprehnite series.Mssbauer spectroscopy indicated that all Fe is present in the trivalent form.The increased Fe content is also reflected in this unit-cell: a = 18.617(5), b = 5.502(2) , c = 4.672(2) , V = 478.5(2) 3 .Pectolite is the main mineral in the mineral assemblage.Its unit-cell parameters refined from powder X-ray diffraction are a = 7.9848(14) , b = 7.0391(19) , c = 7.0243(11) , = 90.53(2), = 95.19(1), = 102.48(2) and V 383.7(1) 3 .Chemical composition of pectolite corresponds to ideal stoichiometry and give the empirical formula Na 1.00 (Ca 2.02 Mn 0.01 Fe 0.01 ) 2.04 Si 3 O 8 (OH 1.04 ) F 0.02 .Other minor minerals of the association are hematite, pyrite and the youngest calcite.The source of mineralization of the circulating fluids can be found in alteration of rock components (feldspars, olivine, glass); however, external input from the surrounding calcareous sediments cannot be excluded.

ABSTRACTThe new mineral bytízite was found in the dump of shaft No. 16, one of the mines in the Příbram uranium and base-metal district, central Bohemia, Czech Republic. Bytízite is associated with chaméanite, příbramite, giraudite, berzelianite, umangite, eskebornite, hakite, tetrahedrite, bukovite, crookesite and uraninite in a calcite-dominant gangue. The new mineral occurs as anhedral grains up to 40 µm, growing together in aggregates up to 300 µm across. Bytízite is steel-grey in colour and has a metallic lustre. Mohs hardness isca. 2–3; the calculated density is 6.324 g cm–3. In reflected light bytízite is grey with a yellowish hue, yellowish and brownish. Bireflectance and pleochroism are weak. Anisotropy is strong with grey to brownish rotation tints. Internal reflections were not observed. The empirical formula, based on electron-microprobe analyses, is (Cu3.00Fe0.01Ag0.01)3.02(Sb0.97As0.06)1.03Se2.94. The ideal formula is Cu3SbSe3, which requires Cu 34.71, Sb 22.16 and Se 43.13, total 100.00 wt.%. Bytízite is orthorhombic,Pnma,a= 7.9594(12),b= 10.5830(14),c= 6.8240(11) Å, withV= 574.82(15) Å3andZ= 4. The strongest reflections of the calculated powder X-ray diffraction pattern [d, Å (I)(hkl)] are: 3.73(37)(210), 3.27(62)(211), 2.867(40)(022), 2.698(100)(122) and 2.646(37)(040). According to the single-crystal X-ray diffraction data (Robs= 0.0437), bytízite is isostructural with synthetic Cu3SbSe3. The structure of bytízite contains two Cu, one Sb, and two Se sites (the latter is occupied both by Se and S atoms). In the structure of both synthetic Cu3SbSe3and bytízite, there are groups of threecis-edge-sharing tetrahedra [Cu3Se8], which are interlinked to a 3D framework by SbSe3groups. Bytízite is named after its type locality, the Bytíz deposit, near the village Bytíz.

Kvačekite is a new mineral species discovered in a sample collected from the now abandoned Bukov uranium mine, western Moravia, Czech Republic. It occurs as rare anhedral grains, up to 15 μm in size, associated with nickeltyrrellite, tyrrellite, berzelianite, hakite-(Zn), hakite-(Cd), eucairite, clausthalite, and gold in calcite gangue. In reflected light, kvačekite is white with a faint yellowish shade; bireflectance, pleochroism and anisotropy are absent. Internal reflections were not observed. Reflectance values for the four COM wavelengths for kvačekite in air [R (%) (λ in nm)] are: 54.9 (470); 53.5 (546); 52.6 (589); and 52.2 (650). The empirical formula, based on electron-microprobe analyses (EPMA), is (Ni0.95Cu0.04Co0.03)Σ1.02Sb1.00(Se0.97S0.01)Σ0.98. The ideal formula is NiSbSe, which requires (in wt.%) Ni 22.63, Sb 46.93, Se 30.44, total 100.00. Kvačekite is cubic, P213, with unit-cell parameters a = 6.09013(13) Å, V = 225.881(15) Å3 and Z = 4. The strongest reflections in the X-ray powder diffraction pattern of synthetic kvačekite [d, Å (I) hkl] are: 3.0458 (11) 200; 2.7242 (100) 201, 210; 2.4867 (71) 211; 1.8632(39) 311; 1.6277(29) 321, 312; and 1.3290 (13) 421. Given the similarity with ullmannite, NiSbS, the crystal structure was refined from the powder X-ray diffraction data starting from those atomic coordinates using the synthetic analogue of kvačekite. Its crystal structure is formed by corner-sharing [NiSb3Se3] octahedra which form a three-dimensional network. The identity of the natural kvačekite and synthetic cubic NiSbSe were confirmed by a study of their chemical composition, reflectance measurements, Raman spectroscopy and electron back-scattered diffraction (EBSD) measurements on the mineral. Kvačekite is named after Milan Kvaček (1930–1993), a prominent Czech mineralogist. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2023-095).

Paulišite, Ca2Zn(CO3)3·2H2O, is a new mineral species discovered in the underground workings at the abandoned mine adit of the first level of the Staročeské Lode, near the historical shaft Šafary, Kaňk near Kutná Hora, central Bohemia, Czech Republic. Paulišite is associated with hydrozincite and aragonite (holotype sample) or calcite, aragonite, hydrozincite, and monohydrocalcite (other samples). The new mineral occurs as crusts, up to 1 cm thick, formed by parallel or radial aggregates of acicular crystals, elongated on [100], up to 5 mm long. Paulišite is colorless to white, with a white streak. It is transparent and has a vitreous luster. Mohs hardness is ca. 4; the calculated density is 2.756 g/cm3. Paulišite is optically biaxial positive, with α = 1.554(1), β = 1.569(2), γ = 1.605(1) (589 nm), and 2V(meas) = 68(2)°. The empirical formula, based on electron-microprobe analyses (n = 11), is Ca2.00(Zn0.97Mg0.02Cu0.01Al0.01)Σ1.01(CO3)3·2H2O based on three cations (excluding C) per formula unit. The ideal formula is Ca2Zn(CO3)3·2H2O, which requires (in wt%) CaO 31.02, ZnO 22.50, CO2 36.51, H2O 9.97, total 100.00. The strongest reflections of the powder X-ray diffraction pattern [d (Å)/(Irel)/hkl] are: 8.226/(100)/011, 6.492/(100)/002, 4.112/(18)/022, 3.246/(35)/004, 3.085/(19)/130, and 2.458/(21)/042. According to single-crystal X-ray diffraction data, paulišite is monoclinic, space group Ia, Z = 4 with a = 6.3007(6), b = 10.6236(11), c = 12.9837(12) Å, β = 90.840(5)°, V = 868.99(15) Å3. The crystal structure was refined to R1 = 0.0229 for 2330 unique reflections with Fo > 4σ(Fo) and 164 refined parameters. It is characterized by Zn(1)-centered tetrahedra, two independent Ca(1)- and Ca(2)-centered polyhedra, and CO3 groups. Heteropolyhedral Ca-Zn-CO3 {001} layers occur in paulišite and are connected along c through CO3 groups and Ca(2)-centered polyhedra, as well as H-bonds. Along with minrecordite, skorpionite, and znucalite, paulišite is the fourth mineral containing Ca, Zn, and (CO3) groups as species-defining elements. Its origin is related to the supergene alteration of ore deposits following the mining activity, probably at low T and basic pH conditions. The mineral and its name, honoring the Czech mineralogist and geologist Petr Pauliš (b. 1956), have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (no. 2023-031).

Vrančiceite is a new mineral species discovered in a sample collected from the old mine dumps of the abandoned Vrančice deposit near Příbram, central Bohemia, Czech Republic. Vrančiceite occurs as rare anhedral grains, up to 100 μm in size, in a calcite gangue, associated with cinnabar, djurleite, galena and hedyphane. Vrančiceite is black, with metallic lustre. Mohs hardness is ca. 2–3, calculated density is 6.652 g.cm–3. In reflected light, vrančiceite is light grey with a yellowish shade; bireflectance, pleochroism and anisotropy are all weak. Internal reflections were not observed. Reflectance values for the four Commission on Ore Mineralogy wavelengths of vrančiceite in air [Rmax, Rmin (%) (λ in nm)] are: 33.6, 31.2 (470); 33.9, 30.6 (546); 31.1, 30.0 (589); and 32.1, 29.1 (650). The empirical formula, based on electron-microprobe analyses, is Cu10.11(4)Ag0.01(1)Hg2.87(4)Sb0.01(1)Bi0.01(1)S7.99(8). The ideal formula is Cu10Hg3S8 (Z = 2), which requires (in wt.%) Cu 42.54, Hg 40.29 and S 17.17, total 100.00. Vrančiceite is triclinic, P$\bar{1}$, with unit-cell parameters a = 7.9681(2), b = 9.7452(3), c = 10.0710(3) Å, α = 77.759(1), β = 76.990(1), γ = 79.422(1)°, V = 737.01(4) Å3 and Z = 2. The strongest reflections of the calculated powder X-ray diffraction pattern [d, Å (I) hkl] are: 3.354 (76) $\bar{2}$01, 3.111 (68) 222, 2.833 (100) 213, 2.733 (93) 231, 2.705 (76) 2$\bar{2}$1 and 2.647 (71) $\bar{2}\bar{1}$2. According to the single-crystal X-ray diffraction data (R1 = 0.0262), the crystal structure of vrančiceite can be described as comprising Cu–S layers, connected through CuS3 polyhedra, giving rise to a three-dimensional framework with channels running along the a axis and hosting linearly coordinated Hg atoms. Structural relations with gortdrumite are discussed. Vrančiceite is named after its type locality, the Vrančice deposit near Příbram. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2022–114).

A re-evaluation of data relating to the crystal structures, phase equilibria, and ideal chemical formulae of the key minerals belonging to the PtS–PdS binary, namely vysotskite, braggite, and cooperite, has led to redefinitions of the ideal chemical formulae for vysotskite and braggite. Results show that vysotskite and braggite are isostructural and crystallize in the space group P42/m. Their crystal structures contain three Me sites and a single S site, giving rise to the general crystal-chemical formula Me(1)2Me(2)2Me(3)4S8. Ordering of Pt and Pd leads to the revised ideal formula of Pd2Pd2Pd4S8 (Z = 1) for vysotskite, which can be simplified to PdS (Z = 8), and a revised ideal formula of Pd2Pt2Pt4S8 (Z = 1) for braggite, which can be simplified to PdPt3S4 (Z = 2). Cooperite, ideally PtS (Z = 8), crystallizes in a related, but different, space group, P42/mmc. Its crystal structure contains a single Me and S site. Both Pt and Pd are disordered over the Me site but with Pt > Pd . Oversimplification of the ideal chemical formulae for all these minerals and failure to consider crystal-structure implications has led to confusion in the literature.Consideration of experimental data combined with that for minerals from world-wide occurrences suggests complete solid solution between vysotskite and braggite, but of a more limited degree between cooperite and braggite, consistent with what would be expected when their respective crystal structures are considered. The maximum Pt possible in braggite should correspond to (Pd0.51Pt0.49)Σ1Pt3S4 (or Pd0.51Pt3.49S4); Pt:Pd = 0.87, which requires Pd 6.29, Pt 78.86, S 14.85, total 100.00 wt.%) and the maximum Pd content, to Pd(Pt0.505Pd0.495)Σ1(Pt1.505Pd0.495)Σ2S4 (or Pd1.99Pt2.01S4); Pt:Pd = 0.50, which requires Pd 28.93, Pt 53.56, S 17.52, total 100.00 wt.%). In light of the complete solid solution between vysotskite and braggite, the 50% rule should be applied to compositions between them. Thus, within the PtS–PdS binary, it is recommended that (1) vysotskite be used for those minerals having compositions ranging from 100 to 56.5 mol.% PdS; (2) braggite, for those having compositions that range from 56.5 to 13 mol.% PdS; and (3) cooperite, for those having <13 mol.%.

Nacareniobsite-(Y), ideally Na3Ca3YNb(Si2O7)2OF3, is a new rinkite-group (seidozerite-supergroup) TS-block mineral from the Darai-Pioz alkaline massif, Tien-Shan mountains, Tajikistan. The mineral is of hydrothermal origin. It occurs as prismatic crystals up to 1 mm long and 0.1 mm thick embedded in an aggregate of coarse-grained reedmergnerite. Associated minerals are reedmergnerite, leucophanite, nordite-(Ce), microcline, zeravshanite, polylithionite, kentbrooksite, yusupovite, fluornatropyrochlore, and quartz. Crystals are pale yellow, transparent, with a vitreous to translucent luster. Nacareniobsite-(Y) has a white streak, uneven to conchoidal fracture, and does not fluoresce under cathode or ultraviolet light. Cleavage is {100} very good, no parting was observed, Mohs hardness is 5, and it is brittle, Dmeas. = 3.49(2) g/cm3, Dcalc. = 3.515 g/cm3. It is biaxial (+) with refractive indices (λ = 590 nm) α = 1.662(2), β = 1.668(2), γ = 1.690(2); 2Vcalc. = 56°. It is nonpleochroic. Nacareniobsite-(Y) is monoclinic, space group P21/c, a = 7.4069(15), b = 5.6540(11), c = 18.787(4) Å, β = 101.36(3)°, V = 771.3(3) Å3. The six strongest reflections in the X-ray powder diffraction data [d(Å), I, (h k l)] are: 3.068, 100, (0 0 6, 1 2, 2 1 0); 2.944, 45, (2 1 1, 1 3); 2.707, 32, (0 2 2, 0 1 6); 5.44, 31, (0 1 1); 1.853, 29, ( 0 2, 2 1 7, 1 9); 3.59, 26, (1 0 4, 0 1 4). The empirical formula calculated on the basis of 18 (O + F) is Na2.82Ca3.06Sr0.14[Y0.37(Nd0.16Ce0.15Dy0.08Gd0.06Sm0.05La0.04Tb0.02Ho0.02Lu0.02Pr0.01Eu0.01Tm0.01Er0.01Yb0.01)Σ0.65]Σ1.02(Nb0.63Ti0.38)Σ1.01(Si4.00O14)O1.00F3.00, Z = 2. The ideal formula is Na3Ca3YNb(Si2O7)2OF3. The crystal structure was refined on a twinned crystal to R1 = 3.50% on the basis of 1788 unique reflections (Fo > 4σFo). It is a framework of TS (Titanium-Silicate) blocks where the TS block consists of HOH sheets (H = heteropolyhedral, O = octahedral) parallel to (100). In the O sheet, the Nb-dominant [6]MO(1) site is ideally occupied by one Nb apfu. The [8]MO(2) and [6]MO(3) sites are ideally occupied by one Na and two Na apfu, respectively. The H sheet contains two unique sites: the [7]MH site, ideally (CaY), is occupied by Ca1.23(Y0.37Ln0.40)Σ0.77, with <MH–φ> = 2.424 Å, and the [7]AP site, ideally Ca2, is occupied by Ca1.61Sr0.14Ln0.25, with <AP–φ> = 2.469 Å. The AP+ MH sites ideally give Ca2(CaY) apfu. The MH and AP polyhedra and Si2O7 groups constitute the H sheet. Linkages of the H and O sheets via common vertices of the MH and AP polyhedra, and Si2O7 groups with MO(1–3) polyhedra, results in the TS block. The TS block in nacareniobsite-(Y) exhibits linkage 1 and has a stereochemistry typical for the rinkite group (Ti + Nb + Zr = 1 apfu) of the seidozerite supergroup. For nacareniobsite-(Y), the ideal structural formula of the form AP2MH2MO4(Si2O7)2(XOM)2(XOA)2 is Ca2(CaY)Na3Nb(Si2O7)2(OF)F2. The mineral is named nacareniobsite-(Y), as it is structurally identical to nacareniobsite-(Ce), ideally Na3Ca3CeNb(Si2O7)2OF3, with Y as the dominant REE. The crystal structure of nacareniobsite-(Ce), has been refined to R1 = 6.80% for 1421 unique (Fo > 4σFo) reflections: space group P21/c, a = 7.4684(15), b = 5.6891(11), c = 18.891(4) Å, β = 101.37(3)°, V = 786.9(3) Å3, Z = 2, Dcalc. = 3.539 g/cm3. The composition of the MH and AP sites in the H sheet has been reassigned as follows: the [7]MH site is occupied by Ca1.28(Ln0.68Y0.04)Σ0.72 where Ce is the dominant lanthanoid, ideally (CaCe) apfu, <MH–φ> = 2.458 Å, and the [7]AP site is occupied by (Ca1.44Na0.09Sr0.04)Σ1.57Ln0.43, ideally Ca2apfu, <AP–φ> = 2.48 Å. The AP+ MH sites ideally give Ca2(CaCe) apfu [cf. (Ca,REE)2(Ca,REE)2apfu, Sokolova & Hawthorne (2008)]. For nacareniobsite-(Ce), the revised ideal structural formula of the form AP2MH2MO4(Si2O7)2(XOM)2(XOA)2 is Ca2(CaCe)Na3Nb(Si2O7)2(OF)F2.

Tvrdýite, Fe2+Fe3+2A13(PO4)4(OH)5(OH2)4·2H2O, is a new phosphate mineral from the abandoned Huber open pit, in the Krásno ore district near Horní Slavkov, western Bohemia, Czech Republic. It was found along with Al-rich beraunite, fluorapatite and pharmacosiderite in a cavity of quartz gangue. Tvrdýite forms acicular to fibrous crystals with diameters in the range 0.5–5 μm and lengths up to 300 μm, partly grouped in radiating aggregates up to 3 mm in size. It has a silvery to olive, greyish green colour with pearly lustre, greyish-white streak and is very brittle with an uneven fracture; individual fibres are somewhat flexible. Cleavage on {100} is good; the Mohs hardness is ∼3–4. The calculated density is 2.834 g cm–3. Tvrdýite is optically biaxial (–), with α = 1.650(2), β = 1.671(1) and γ = 1.677(1) (white light); 2V = 56(1)°; dispersion: r > v, strong; optical orientation: Z = b, X ≈ a, Y ≈ c; pleochroism: X = greenish blue, Y = yellowish orange, Z = yellowish orange (X>> Y > Z). Tvrdýite is monoclinic, space group C2/c, a = 20.564(4), b = 5.101(1), c = 18.883(4) Å, β = 93.68(3)° and V = 1976.7(7) Å3, Z = 4, a:b:c= 4.031:1:3.702. The strongest eight lines in the powder X-ray diffraction (XRD) pattern [d in Å (I)(hkl)] are 10.227 (100) (200), 9.400 (6) (002), 7.156 (14) (202), 5.120 (7) (400), 3.416 (11) (600), 3.278 (6) (602), 2.562 (5) (800) and 2.0511 (3) (10,0,0). Chemical analyses by electron microprobe yielded MnO 0.01, ZnO 5.08, , FeO 4.31, Fe2O3 21.16, Al2O316.71, P2O5 32.64, As2O5 2.56, F 0.53, H2O (calc.) 17.84, O = F –0.22, total 100.62 wt.%. The resulting empirical formula, calculated on the base of 27 anions, obtained from the crystal structure, is Zn0.52Fe2+0.50Fe3+2.21Al2.75(PO4)3.86(AsO4)0.19OH4.60F0.23(OH2)4·2H2O. The ideal formula, Fe2+Fe3+2Al3(PO4)4(OH)5(OH2)4-2H2O, requires FeO 8.75, Fe2O3 19.44, Al2O3 18.62, P2O5 34.56, H2O 18.64, total 100.00 wt.%. The crystal structure of tvrdýite was solved from single-crystal data (synchrotron beamline) and refined to R1 = 0.038 for 2276 reflections with I > 2σ(I). Tvrdýite is isostructural with beraunite, but contains dominant Al in two of the four independent M sites, which are all occupied by Fe in beraunite.

An interesting mineral association of paratacamite, nantokite, cuprite and an unnamed NaCuCl-arsenate was found at sample from the Jáchymov ore district (probably 12th level of the Geschieber vein, Svornost mine), Krušné hory Mountains, Czech Republic. Paratacamite occurs as light greenish-blue to whitish green irregular aggregates up to 2 mm in size. It is trigonal, space group R-3, the unit-cell parameters refined from X-ray powder diffraction data are: a 13.656(8), c 14.042(11) Å and V 2268(2) Å3; its chemical analyses correspond to the empirical formula Cu3.00(Cu0.56 Ni0.38Co0.03Ca0.03)Σ1.00Cl1.91(OH)6.09 on the basis of 4 cations apfu. Nantokite forms aggregates up to 200 μm in size replacing earlier native copper. It is cubic, space group F-43m, the unit-cell parameter refined from X-ray powder diffraction data are: a 5.4164(12) Å and V 158.90(11) Å3; its chemical analyses correspond to the empirical formula Cu1.00Cl1.00 on the base of 2 apfu. Cuprite was identified only by X-ray powder diffraction data, it is cubic, space group Pn3m with unit-cell parameter a 4.2736(4) Å and V 78.08(2) Å3. An unnamed NaCuCl-arsenate occurs as lavendulane-like blue crusts with an area of up to 5 × 8 mm on altered rock or earlier paratacamite. The crusts are composed of hemispherical aggregates up to 0.2 mm in size with a very finely crystalline surface. Its X-ray powder diffraction pattern (d(Å)/Iobs: 12.808/100, 4.944/25, 3.114/16, 2.738/17, 2.516/20) does not correspond to any approved mineral species. The chemical composition of NaCuCl-arsenate is close to ideal formula NaCu5(AsO4)2(AsO3OH)2Cl·3H2O and its empirical formula based on As+P+Si+S = 4 apfu is Na1.07Ca0.24(Cu4.70Ni0.27Co0.02Zn0.01Mn0.01)Σ5.01 (AsO4)2.00[(AsO3OH)1.73(AsO4)0.13(SiO4)0.08(SO4)0.04(PO4)0.02]Σ2.00Cl1.26·3H2O. The origin of the described mineral association is connected with (sub)recent weathering of native copper in quartz veinlets in altered granite rocks.

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 Krušné 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 (Ag 15.95 Cd 0.02 ) Σ15.97 (As 1.82 Sb 0.11 ) Σ1.93 (S 11.03 Cl 0.05 Te 0.01 ) Σ11.09 . The ideal formula is Ag 16 As 2 S 11 , which requires (in wt.%) Ag 77.45, As 6.72 and S 15.83, total of 100.00. Argentopearceite is trigonal, P 321, a = 14.8583(5), c = 12.3038(15) Å, with V = 2352.38(15) Å 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 > 3σ( 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.