On the basis of extensive studies of synthetic perovskite-structured compounds it is possible to derive a hierarchy of hettotype structures which are derivatives of the arisotypic cubic perovskite structure (ABX3), exemplified by SrTiO3 (tausonite) or KMgF3 (parascandolaite) by: (1) tilting and distortion of the BX6 octahedra; (2) ordering of A- and B-site cations; (3) formation of A-, B- or X-site vacancies. This hierarchical scheme can be applied to some naturally-occurring oxides, fluorides,hydroxides, chlorides, arsenides, intermetallic compounds and silicates which adopt such derivative crystal structures. Application of this hierarchical scheme to naturally-occurring minerals results in the recognition of a perovskite supergroup which is divided into stoichiometric and non-stoichiometricperovskite groups, with both groups further divided into single ABX3 or double A2BB'X6 perovskites. Subgroups, and potential subgroups, of stoichiometric perovskites include: (1) silicate single perovskites of the bridgmanite subgroup;(2) oxide single perovskites of the perovskite subgroup (tausonite, perovskite, loparite, lueshite, isolueshite, lakargiite, megawite); (3) oxide single perovskites of the macedonite subgroup which exhibit second order Jahn-Teller distortions (macedonite, barioperovskite); (4) fluoride singleperovskites of the neighborite subgroup (neighborite, parascandolaite); (5) chloride single perovskites of the chlorocalcite subgroup; (6) B-site cation ordered double fluoride perovskites of the cryolite subgroup (cryolite, elpasolite, simmonsite); (7) B-site cation orderedoxide double perovskites of the vapnikite subgroup [vapnikite, (?) latrappite]. Non-stoichiometric perovskites include: (1) A-site vacant double hydroxides, or hydroxide perovskites, belonging to the söhngeite, schoenfliesite and stottite subgroups; (2) Anion-deficient perovskitesof the brownmillerite subgroup (srebrodolskite, shulamitite); (3) A-site vacant quadruple perovskites (skutterudite subgroup); (4) B-site vacant single perovskites of the oskarssonite subgroup [oskarssonite]; (5) B-site vacant inverse single perovskites of the coheniteand auricupride subgroups; (6) B-site vacant double perovskites of the diaboleite subgroup; (7) anion-deficient partly-inverse B-site quadruple perovskites of the hematophanite subgroup.

Gold occurrences have been reported in the northeastern part of Goiás State since the beginning of the 18th Century. The main mineralization is associated with Paleoproterozoic peraluminous, syntectonic granites of the Aurumina Suite and associated metasedimentary,graphite-bearing country rocks of the Ticunzal Formation. In the Buraco do Ouro gold mine, the mineralization is hosted in muscovite-quartz mylonite in a silicified shear zone near the contact between biotite-muscovite granite and paragneiss of the Ticunzal Formation. The ore mineralogy consistsof gold, paraguanajuatite (Bi2Se3), kalungaite (PdAsSe), isomertieite [Pd11Sb2As2], mertieite II [Pd8(Sb,As)3], sperrylite (PtAs2), padmaite (PdBiSe), bohdanowiczite (AgBiSe2), clausthalite (PbSe),krutaite (CuSe2), ferroselite (FeSe2), uraninite (UO2) and unnamed Ag-Pb-Bi-Se minerals. Local magnetite concentrations and rare chalcopyrite and pyrite are also associated with both mineralized and barren mylonites in a gangue consisting of muscovite, quartzand rare tourmaline. High TiO2 muscovite clasts in the ore are interpreted as the magmatic muscovite of the original granite, and the mineralization is considered to be synchronous with the syntectonic granite intrusion during syn-emplacement shearing and alteration. The associationbetween granitic rocks and platinum-group element (PGE)-bearing gold mineralization observed in the Buraco do Ouro mine is uncommon and unique in the context of the Aurumina Suite and the Ticunzal Formation, where gold deposits and occurrences are gold-only. The chemical data suggest the possibilityof a solid solution between paraguanajuatite and bohdanowiczite. In addition, a complex intergrowth occurs between paraguanajuatite, clausthalite and Ag-Pb-Bi-Se phases, one of which, a Pb-Bi-Se phase could represent a new mineral. Uraninite is identified for the first time in this mineralassemblage and its concentration in the ore seems important, as revealed by high gamma spectrometric measurements in the samples collected in the mine. The association between gold and uranium constitutes a regional signature, observed in both gold and uranium deposits in the Cavalcante region.

Kyawthuite, Bi3+Sb5+O4, is a new gem mineral found as a waterworn crystal in alluvium at Chaung-gyi-ah-le-ywa in the Chaung-gyi valley, near Mogok, Burma (Myanmar). Its description is based upon a single sample, which was faceted into a 1.61-carat gem.The composition suggests that the mineral formed in a pegmatite. Kyawthuite is monoclinic, space group I2/c, with unit cell dimensions a = 5.4624(4), b = 4.88519(17), c = 11.8520(8) Å, β = 101.195(7)°, V = 310.25(3) Å3and Z = 4. The colour is reddish orange and the streak is white. It is transparent with adamantine lustre. The Mohs hardness is 5½. Kyawthuite is brittle with a conchoidal fracture and three cleavages: {001} perfect, {110} and {110} good. The measured density is 8.256(5) g cm–3and the calculated density is 8.127 g cm–3. The mineral is optically biaxial with 2V = 90(2)°. The predicted indices of refraction are α = 2.194, β = 2.268, γ = 2.350. Pleochroism is imperceptible and the optical orientation is X = b; Y≈ c; Z ≈ a. Electron microprobe analyses, provided the empirical formula (Bi0.823+Sb0.183+)∑1.00(Sb0.995+Ta0.015+)∑1.00O4. The Raman spectrumis similar to that of synthetic Bi3+Sb5+O4. The infrared spectrum shows a trace amount of OH/H2O. The eight strongest powder X-ray diffraction lines are [dobs in Å(I)(hkl)]: 3.266(100)(112), 2.900(66)(112), 2.678(24)(200), 2.437(22)(020,114), 1.8663(21)(024), 1.8026(43)(116,220,204), 1.6264(23)(224,116) and 1.5288(28)(312,132). In the crystal structure of kyawthuite (R1 = 0.0269 for 593 reflections with Fo > 4σF), Sb5+O6 octahedrashare corners to form chequerboard-like sheets parallel to {001}. Atoms of Bi3+, located above and below the open squares in the sheets, form bonds to the O atoms in the sheets, thereby linking adjacent sheets into a framework. The Bi3+ atom is in lopsided 8 coordination,typical of a cation with stereoactive lone electron pairs. Kyawthuite is isostructural with synthetic β-Sb2O4 and clinocervantite (natural β-Sb2O4).

Two new members of the atacamite family were discovered recently in the Sadamisaki Peninsula, Ehime Prefecture, Japan. Iyoite, MnCuCl(OH)3, is an Mn-Cu ordered analogue of botallackite, while misakiite, Cu3Mn(OH)6Cl2, is an Mn-rich analogueof kapellasite. Both minerals occur in manganese ore crevices in close association with one another. Iyoite forms radial and dendritic aggregates consisting of pale green, bladed crystals. Misakiite commonly exists in emerald green, tabular, hexagonal crystals. The densities of iyoite andmisakiite were calculated to be 3.22 and 3.42 g cm–3 based on their empirical formulae and powder X-ray diffraction data. Under the same axial setting of botallackite, iyoite is monoclinic, space group P21/m, a = 5.717(2), b = 6.586(2), c= 5.623(3) Å, β = 88.45(3)° and V = 211.63(15) Å3. Misakiite is trigonal, space group P3m1, with a = 6.4156(4), c = 5.7026(5) Å and V = 203.27(3) Å3. The structures of both mineralsare classified as layer type and the two are closely related. These new minerals were formed by the reaction between seawater and naturally-occurring manganese ores including native copper. These minerals are challenging to produce synthetically. Misakiite was synthesized successfully usinga hydrothermal method, while iyoite could not be made.

The new mineral gazeevite, BaCa6(SiO4)2(SO4)2O (R3m, a = 7.1540(1), c = 25.1242(5) Å, V = 1113.58(3) Å3, Z = 3), was found in an altered xenolith in rhyodacites ofthe Shadil-Khokh volcano, Southern Ossetia and at three localities in larnite pyrometamorphic rocks of the Hatrurim Complex; Nahal Darga and Jabel Harmun, Judean Mountains, Palestinian Autonomy, and Har Parsa, Negev Desert, Israel. Larnite, fluorellestadite–fluorapatite, srebrodolskite–brownmilleriteand mayenite-supergroup minerals are the main minerals commonly associated with gazeevite. Gazeevite is isostructural with zadovite and aradite; the 1:1 type AB6(TO4)2(TO4)2W, occurs together with the structurallyrelated minerals of the nabimusaite series, 3:1 type AB12(TO4)4(TO4)2W3, where A = Ba, K, Sr...; B = Ca, Na...; T = Si, P, V5+, S6+, Al...; W = O2–,F–. Single antiperovskite layers {[WB6](TO4)2} in the structure type of gazeevite–zadovite and triple {[W3B12](TO4)4} layers in arctite–nabimusaite areintercalated with single A(TO4) layers. These minerals with an interrupted antiperovskite structure are characterized by a modular layered structure derived from hatrurite, Ca3(SiO4)O. Gazeevite is colourless, transparent, with a white streakand vitreous lustre. Gazeevite is brittle, shows pronounced parting and imperfect cleavage on {001}; it is uniaxial (–), ω = 1.640(3), ε = 1.636(2) (λ = 589 nm) and nonpleochroic; Mohs' hardness is ∼4.5, VHN50 = 417 kg mm–2. The calculateddensity is = 3.39 g cm–3. The main lines of the calculated powder X-ray diffraction pattern are as follows (d(Å)/I/hkl): 3.58/100/110, 3.07/91/021, 2.76/47/116, 1.789/73/220, 3.29/60/113, 2.78/36/024, 2.12/25/125, 2.21/21/208. Raman spectra of gazeeviteare compared with spectra of other minerals. The formation of gazeevite and minerals of the nabimusaite–dargaite series is connected with high-temperature alteration of an early assemblage of clinker minerals affected by later fluids generated by volcanic activity or combustion processes.

It is common practice to estimate a mean diameter for spherical or sub-spherical particles or vesicles in a rock by multiplying the average diameter of the approximately circular cross-sections visible in thin section by a factor of 1.273. This number-weighted average may be dominatedby the hard-to-measure fine tail of the size distribution, and is unlikely to be representative of the average particle diameter of greatest interest for a wide range of geological problems or processes. Average particle size can be quantified in a variety of ways, based on the mass or surfacearea of the particles, and here we provide exact relations of these different average measures to straightforward measurements possible in thin section, including an analysis of how many particles to measure to achieve a desired level of uncertainty. The use of average particle diameter isillustrated firstly with a consideration of the accumulation of olivine phenocrysts on the floor of the 135 m thick picrodolerite/crinanite unit of the Shiant Isles Main Sill. We show that the 45 m thick crystal pile on the sill floor could have formed by crystal settling within about a year.The second geological example is provided by an analysis of the sizes of exsolved Fe-rich droplets during unmixing of a basaltic melt in a suite of experimental charges. We show that the size distribution cannot be explained by sudden nucleation, followed by either Ostwald ripening or Browniancoalescence. We deduce that a continuous process of droplet nucleation during cooling is likely to have occurred.

Norilskite, (Pd,Ag)7Pb4 is a new platinum-group mineral discovered in the Mayak mine of the Talnakh deposit, Russia. It forms anhedral grains in aggregates (up to ∼400 μm) with polarite, zvyagintsevite, Pd-rich tetra-auricupride, Pd-Pt bearing auricupride,Ag-Au alloys, (Pb,As,Sb) bearing atokite, mayakite, Bi-Pb-rich kotulskite and sperrylite in pentlandite, cubanite and talnakhite. Norilskite is brittle, has a metallic lustre and a grey streak. Values of VHN20 fall between 296 and 342 kg mm–2, with a mean valueof 310 kg mm–2, corresponding to a Mohs hardness of ∼4. In plane-polarized light, norilskite is orange-brownish pink, has moderate to strong bireflectance, orange-pink to greyish-pink pleochroism, and strong anisotropy; it exhibits no internal reflections. Reflectancevalues of norilskite in air (Ro, Re' in %) are: 51.1, 48.8 at 470 nm, 56.8, 52.2 at 546 nm, 59.9, 53.5 at 589 nm and 64.7, 55.5 at 650 nm. Sixteen electronmicroprobe analyses of natural norilskite gave an average composition: Pd 44.33, Ag 2.68, Bi 0.33 and Pb 52.34, total99.68 wt.%, corresponding to the empirical formula (Pd6.56Ag0.39)∑6.95(Pb3.97Bi0.03)∑4.00 based on 4 Pb + Bi atoms; the average of eight analyses on synthetic norilskite is: Pd 42.95, Ag 3.87 and Pb 53.51, total 100.33wt.%, corresponding to (Pd6.25Ag0.56)∑6.81Pb4.00. The mineral is trigonal, space group P3121, with a = 8.9656(4), c = 17.2801(8) Å, V = 1202.92(9) Å3 and Z = 6. The crystalstructure was solved and refined from the powder X-ray diffraction data of synthetic (Pd,Ag)7Pb4. Norilskite crystallizes in the Ni13Ga3Ge6 structure type, related to nickeline. The strongest lines in the powder X-ray diffraction patternof synthetic norilskite [d in Å (I) (hkl)] are: 3.2201(29)(023,203), 2.3130(91)(026,206), 2.2414(100)(220), 1.6098(28)(046,406), 1.3076(38)(246,462), 1.2942(18)(600), 1.2115(37)(22.12,12.13), 0.9626(44) (06.12,60.12). The mineral is named for the locality, the Noril'sk district in Russia.

The new mineral hansesmarkite (IMA2015-067), Ca2Mn2Nb6O19·20H2O, was discovered at the AS Granit larvikite quarry in Tvedalen, Larvik, Vestfold, Norway. Hansesmarkite forms faintly yellow crystals up to 0.3 mm or thin coatingsin patches on gonnardite. Hansesmarkite is biaxial (+) with refractive indices (white light): α = 1.683(2), β = 1.698(2) and γ = 1.745(3); 2V(meas.) = 60.7(6)° and 2V(calc.) = 60.3°. The mineral exhibits moderate dispersion (r > v)and is pleochroic with X (almost colourless) < Y ( pale yellow) << Z (orangey yellow). The optical orientation is X ^ c = 20°, Y ^ b = 16° and Z ^ a = 5°. The empirical formula based on five electron probemicroanalyses and calculated based on Nb = 6 apfu is (Ca1.93Na0.02K0.01)∑1.96(Mn1.79Fe0.11)∑1.90Nb6O18.84·20H2O, with H2O determined from the structure solution.The mineral is triclinic, P1, with a = 9.081(4), b = 9.982(8), c = 10.60(1) Å, α = 111.07(8), β = 101.15(6), γ = 99.39(5)°, V = 850.8(13) Å3 and Z = 1. The structure was solved at 120 K because of thermalinstability of the mineral and refined to R1 = 2.50% for Fo > 4σ. The strongest reflections in the x-ray diffraction diagram are: [dobs. in Å (I)(hkl)] 9.282(36)(001), 8.610(100)(100, 011), 3.257(30)(031, 131)and 3.058(18)(130, 212). Hansesmarkite is the third naturally occurring hexaniobate in which six edge-sharing Nb-octahedra form the Lindqvist ion. These are linked via Mn-octahedra forming rods along [100] and Ca is located between the rods, creating a three dimensional structure via hydrogen bonds.

Hydroxycalciomicrolite, Ca1.5Ta2O6(OH) is a new microlite-group mineral found in the Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil. It occurs as isolated octahedral and as a combination of octahedral and rhombic dodecahedral crystals, up to1.5 mm in size. The crystals are yellow and translucent, with a white streak and vitreous to resinous lustre. The mineral is brittle, with a Mohs hardness of 5–6. Cleavage is not observed and fracture is conchoidal. The calculated density is 6.176 g cm–3. Hydroxycalciomicroliteis isotropic, ncalc. = 2.010. The infrared and Raman spectra exhibit bands due to O–H stretching vibrations. The chemical composition determined from electron microprobe analysis (n = 13) is (wt.%): Na2O 0.36(8), CaO 15.64(13), SnO2 0.26(3),Nb2O5 2.82(30), Ta2O5 78.39(22), MnO 0.12(2), F 0.72(12) and H2O 1.30 (from the crystal structure data), O = F –0.30, total 99.31(32), yielding an empirical formula, (Ca1.48Na0.06Mn0.01)∑1.55(Ta1.88Nb0.11Sn0.01)∑2.00O6.00[(OH)0.76F0.20O0.04].Hydroxycalciomicrolite is cubic, with unit-cell parameters a = 10.4205(1) Å, V = 1131.53(2) Å3 and Z = 8. It represents a pyrochlore supergroup, microlite-group mineral exhibiting P4332 symmetry, instead of Fd3m. Thereduction in symmetry is due to long-range ordering of Ca and vacancies on the A sites. This is the first example of such ordering in a natural pyrochlore, although it is known from synthetic compounds. This result is promising because it suggests that other species with P4332or lower-symmetry space group can be discovered and characterized.

Unusual speleothems, associated with hyperalkaline (pH > 12) groundwaters have formed within a shallow, abandoned railway tunnel at Peak Dale, Derbyshire, UK. The hyperalkaline groundwaters are produced by the leaching of a thin layer (<2 m) of old lime-kiln waste on the soil-bedrock surface above the tunnel by rainwater. This results in a different reaction and chemical process to that more commonly associated with the formation of calcium carbonate speleothems from Ca-HCO3-type groundwaters and degassing of CO2. Stalagmites within the Peak Daletunnel have grown rapidly (averaging 33 mm y–1), following the closure of the tunnel 70 years ago. They have an unusual morphology comprising a central sub-horizontally-laminated column of micro- to nano-crystalline calcium carbonate encompassed by an outer sub-vertical assymetricripple-laminated layer. The stalagmites are composed largely of secondary calcite forming pseudomorphs (<1 mm) that we believe to be predominantly after the 'cold climate' calcium carbonate polymorph, ikaite (calcium carbonate hexahydrate: CaCO3·6H2O), withminor volumes of small (<5 μm) pseudomorphs after vaterite. The tunnel has a near constant temperature of 8–9°C, which is slightly above the previously published crystallization temperatures for ikaite (<6°C). Analysis of a stalagmite actively growing at the time ofsampling, and preserved immediately within a dry nitrogen cryogenic vessel, indicates that following crystallization of ikaite, decomposition to calcite occurs rapidly, if not instantaneously. We believe this is the first occurrence of this calcium carbonate polymorph observed within speleothems.

Żabińskiite, ideally Ca(Al0.5Ta0.5)(SiO4)O, was found in a Variscan granitic pegmatite at Piława Górna, Lower Silesia, SW Poland. The mineral occurs along with (Al,Ta,Nb)- and (Al,F)-bearing titanites, a pyrochlore-supergroupmineral and a K-mica in compositionally inhomogeneous aggregates, ∼120 μm × 70 μm in size, in a fractured crystal of zircon intergrown with polycrase-(Y) and euxenite-(Y). Żabińskiite is transparent, brittle, brownish, with a white streak, vitreous lustre and a Mohs hardness of ∼5. The calculated density for the refined crystal is equal to 3.897 g cm–3, but depends strongly on composition. The mineral is non-pleochroic, biaxial (–), with mean refractive indices ≥1.89. The (Al,Ta,Nb)-richest żabińskiite crystal,(Ca0.980Na0.015)∑=0.995(Al0.340Fe3+0.029Ti0.298V0.001Zr0.001Sn0.005Ta0.251Nb0.081)∑=1.005[(Si0.988Al0.012)O4.946F0.047(OH)0.007)∑=5.000];60.7 mol.% Ca[Al0.5(Ta,Nb)0.5](SiO4)O; is close in composition to previously described synthetic material. Żabińskiite is triclinic (space group symmetry A1) and has unit-cell parameters a = 7.031(2) Å, b = 8.692(2) Å,c = 6.561(2) Å, α = 89.712(11)°, β = 113.830(13)°, γ = 90.352(12)° and V = 366.77 (11) Å3. It is isostructural with triclinic titanite and bond-topologically identical with titanite and other minerals of the titanite group.Żabińskiite crystallized along with (Al,Ta,Nb)-bearing titanites at increasing Ti and Nb, and decreasing Ta activities, almost coevally with polycrase-(Y) and euxenite-(Y) from Ca-contaminated fluxed melts or early hydrothermal fluids.

The crystal structure of the first thallium-bearing gold telluride, honeaite Au3TlTe2, is reported and its topological novelty discussed. Honeaite is orthorhombic, space group Pbcm and unit-cell parameters a = 8.9671(4), b = 8.8758(4), c= 7.8419(5) Å, V = 624.14(6) Å3 (Z = 4). Its structure has been refined to R1 = 0.033, wR2 = 0.053, Goof = 1.087. The structure is based upon a corrugated double-sheet comprising two sub-sheets, each composed of six-memberedrings of corner-linked TeAu3 pyramids in which the Te lone pair is stereoactive. Rows of thallium atoms lie in the grooves between sheets and provide the only inter-sheet connectivity via Tl-Au bonds. There is extensive Au-Au bonding linking the two sub-sheets of the double-sheet.The structure is distinct from those of the 1:2 (Au,Ag)-tellurides: calaverite AuTe2, sylvanite AuAgTe4 and krennerite Au3AgTe8, which are based upon sheet structures with no connecting inter-sheet atoms. It also differs fundamentally from the structuresof synthetic phases Ag3TlTe2 and Ag18Tl4Te11, both of which have an analogous stoichiometry. In contrast to the pyramidal TeAu3 group of honeaite and krennerite, Ag does not form the corresponding TeAg3 group in itstellurides.

The new mineral juansilvaite (IMA2015-080), Na5Al3[AsO3(OH)]4[AsO2(OH)2]2(SO4)2·4H2O, was foOptically, juansilvaiteund at the Torrecillas mine, Iquique Province, Chile, where it occurs as asecondary alteration phase in association with anhydrite, canutite, halite, sulfur and a mahnertite-like phase. Juansilvaite occurs as bright pink blades up to ∼0.5 mm long grouped in tightly intergrown radial aggregates and also as opaque dull pale pink rounded aggregates. Blades areflattened on {001}, elongated on [100] and exhibit the forms {001}, {111} and {201}. Crystals are transparent, with vitreous lustre and white streak. The Mohs hardness is ∼2½, tenacity is brittle and fracture is irregular. Cleavage is very good on {001}. The measured density is3.01(2) g cm–3 and the calculated density is 3.005 g cm–3. Optically, juansilvaite is biaxial (+) with α= 1.575(1), β = 1.597(1), γ= 1.623(1) and 2V = 86(1)° (measured in white light). Dispersion is r < v, slight, andthe orientation is X = b; Z ^ c = 27° in the obtuse angle β. The pleochroism is X > Y ≈ Z in shades of pale pink. The mineral is slowly soluble in dilute HCl at room temperature. The empirical formula, determined from electron-microprobeanalyses, is Na4.95Al2.28Fe0.503+Mn0.213+Cu0.04As5.92S1.83O36H17.37. Juansilvaite is monoclinic, C2/c, a = 18.1775(13), b = 8.6285(5), c= 18.5138(13) Å, β = 90.389(6)°, V = 2903.7(3) Å3 and Z = 4. The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 9.25(100)(002), 7.20(34)(111), 4.545(34)(400), 3.988(39)(114), 3.363(42)(314), 3.145(66)(512,420), 2.960(68)(422,422) and 2,804(33)(131,423). The structure of juansilvaite (R1 = 3.82% for 2040 Fo > 4σF reflections) contains layers made up of alternating corner-linked Al–O octahedra and acid-arsenate tetrahedra. Sodium cations occur both peripheral to the layers and within cavities in the layers. An SO4 tetrahedron and an H2O group also are in the interlayer region.

Hansblockite, ideally (Cu,Hg)(Bi,Pb)Se2, is a new selenide from the El Dragón mine, Bolivia. It typically occurs in thin subparallel plates intergrown with two unnamed Cu–Hg–Pb–Bi–Se species, clausthalite, Corich penroseite and petrovicite.It also forms subhedral to anhedral grains up to 150 μm long and 50 μm wide. Hansblockite is non-fluorescent, black and opaque with a metallic lustre and black streak. It is brittle, with an irregular fracture and no obvious parting and cleavage. The VHN20 values range from37 to 50 (mean 42) kg mm–2 (Mohs hardness 2–2½). In plane-polarized incident light, hansblockite is cream to light grey in colour, weakly bireflectant and weakly pleochroic from greyish cream to cream. Under crossed polars, hansblockite is weakly anisotropic withkhaki to pale blue rotation tints. The reflectance values in air for the Commission on Ore Mineralogy (COM) standard wavelengths are: 47.3–48.1 (470 nm), 47.4–49.9 (546 nm), 47.1–49.0 (589 nm) and 46.6–48.5 (650 nm). The mean composition is Cu 9.31, Ag 0.73, Hg 11.43,Pb 3.55, Ni 0.17, Co 0.03, Bi 31.17, Se 34.00, total 100.39 wt.%. The mean empirical formula (based on 4 apfu) is (Cu0.68Hg0.27Ag0.03Ni0.01)∑=0.99(Bi0.69Pb0.31)∑=1.00Se2.01. The simplifiedformula is (Cu,Hg) (Bi,Pb)Se2. Hansblockite is monoclinic, space group P21/c, with a = 6.853(1), b = 7.635(1), c = 7.264(1) Å, β = 97.68(1)°, V = 376.66(9) Å3 and Z = 4. Density is 8.26 gcm–3. The five strongest powder X-ray diffraction lines [d in Å (I/I0) (hkl)] are: 3.97 (90) (111), 3.100 (40) (121), 2.986 (100) (211), 2.808 (50) (112) and 2.620 (50) (022). Hansblockite represents the monoclinic polymorph ofgrundmannite, CuBiSe2, with Hg and Pb being essential in stabilizing the monoclinic structure via the coupled substitution Cu+ + Bi3+⇔ Hg2+ + Pb2+. The mineral name is in honour of Hans Block (1881–1953), in recognition of hisimportant role in boosting Bolivian ore mining.

Pink-orange crystals of a composition within the ferri-obertiite compositional space were found in vesicles in a pale beige silicate vein found from a basalt quarry at Mount Rothenberg, Eifel district, Germany. Associated minerals are potassic feldspar, alpha quartz paramorphic afterbeta quartz, eifelite (the second occurrence after the Caspar quarry at Bellerberg volcano, Eifel region), tridymite, rutile, roedderite and other amphiboles. The ideal formula of ferri-obertiite is ANaBNa2C(Mg3Fe3+Ti)TSi8O22WO2; the empirical formula derived for the holotype specimen from Mount Rothenberg from the results of electron-microprobe analysis and single-crystal structure refinement is A(Na0.76K0.22)∑0.98B(Na1.61Ca0.35Mn0.042+)∑2.00C(Mg3.58Mn0.112+Fe0.623+Ti0.664+Cr0.013+Zn0.01Ni0.01)∑5.00T(Si7.82Ti0.124+Al0.06)∑8.00O22W[O1.26F0.55(OH)0.19]∑2.00. The unit-cell dimensions are a = 9.7901(7), b = 17.9354(13), c = 5.2892(4)Å, β= 104.142(2)°, V = 900.58 (11) Å3. The space group is C2/m, Z = 2. Ferri-obertiite is biaxial (+), with α = 1.664, β = 1.680, γ = 1.722, all ±0.002 and 2V (meas.) = 66.4(3)o, 2V (calc.) = 64.7o.The strongest eight reflections in the powder X-ray pattern [d values (in Å), I, (hkl)] are: 2.704, 100, (151); 3.116, 76, (310); 3.388, 72, (131); 8.931, 72, (110); 2.529, 67, (202); 2.583, 39, (061); 2.160, 38, (261); 3.260, 37, (240). Both the mineral and thename have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2015-079); the rock specimen has been deposited at the Museo di Mineralogia, Dipartimento di Scienze della Terra e dell'Ambiente, Universitàdegli Studi di Pavia, under the code 2015-02.

Kamotoite-(Y) is a rare supergene product of uraninite hydration–oxidation weathering and its structure is unknown. Based on single-crystal X-ray diffraction data collected with high-redundancy using a microfocus source, kamotoite-(Y) is monoclinic, has space group P21/n,with a = 12.3525(5), b = 12.9432(5), c = 19.4409(7) Å, β = 99.857(3)°, V = 3069.8(2) Å3 and Z = 4. Crystals are pervasively twinned (two-fold rotation around [0.75 0 0.75]), giving a strongly pseudo-orthorhombic diffractionpattern. The pseudoorthorhombic pattern can be described with an orthorhombic super-cell (transformation matrix 0,1,0/1,0,1/3,0,1), approximately four times larger in volume then a true monoclinic unit cell. This unit-cell is the same as the cell given elsewhere for the structure of bijvoetite-(Y),another (REE)-containing uranyl carbonate. The successful structure solution and refinement (R = 0.044 for 6294 unique observed reflections), carried out using our choice of unit cell, as well as the superstructure refinement and comparison of the original structure data forbijvoetite-(Y) reveal that these two crystal structures are identical. The crystal structure of kamotoite-(Y) consists of electroneutral sheets of the bijvoetite-(Y) uranylanion topology and an interlayer with H2O molecules not-coordinated directly to any metal cation. Despite determinationof the kamotoite-(Y) structure and demonstration that bijvoetite-(Y) has the same structure, the identity of these two minerals cannot be proved without additional study of the holotype material.

The distribution of Au and associated trace elements in pyrite and arsenopyrite from late Archean Hutti and Hira-Buddini orogenic gold deposits, eastern Dharwar Craton, southern India was investigated by laser ablation-inductively coupled plasma-mass spectrometry. X-ray element maps acquired by electron probe microanalyser reveal oscillatory zoning of Co and As indicating the crystallization of pyrite and arsenopyrite in an episodic fluid flow regime in which fluid salinity fluctuated due to fault-valve actions. The absence of any relationship between Au and As in pyrite obviate the role of As in the incorporation of Au into pyrite, particularly here and may be generally the case in orogenic gold deposits. On the other hand, positive correlations of Au with Cu, Ag and Te suggest possible influence of these chalcophile elements in the enhanced gold concentrationin sulfides. Pb-Bi-Te-Au-Ag bearing micro-particles (<2 μm) are observed exclusively in micro-fractures and pores in arsenopyrite. The absence of replacement features and element gradient suggests direct precipitation of Pb, Bi, Te, Au and Ag from a fluid that was unreactive towards arsenopyrite. An intermittent fall in fluid pressure caused by the fault-valve action would have resulted in the sporadic precipitation of Au, Pb, Ag, Bi and Te.

New Pd-Tl-(Bi,As)-rich compounds are described from the Anomal'nyi Cu-PGE deposit, Kondyor alkaline ultramafic complex, northeastern Russia. They occur in vein-type settings associated with bodies of 'kosvite' (magnetite-rich clinopyroxenite) in the dunite-(peridotite) core, in pegmatiticand micaceous rocks. The ore zones are substantially enriched in phlogopite; they consist of diopside, disseminated titaniferous magnetite and fluorapatite (Sr-bearing). The observed assemblages of ore minerals include sulfides of the chalcopyrite-bornite-(secondary chalcocite) associationand various species of platinum-group minerals (PGM) [isomertieite or arsenopalladinite rich in Sb, mertieite-II, mertieite-I, sobolevskite, kotulskite, merenskyite, zvyagintsevite, palarstanide, paolovite, sperrylite, maslovite or moncheite, hollingworthite and unnamed species of PGM] anda Ag-Au alloy. The oxides [Pd4(Bi,Te,Tl)O6 and Pd4(Tl,Bi,Te)O6] probably formed in situ by oxidation reactions at the expense of the associated PGM intergrowths. These involve palladium bismuthide-thallide phases, Pd5(Tl,As,Bi)and Pd5(As,Tl,Bi), which are documented here for the first time. A fairly evolved environment, enriched in Cu, Pd, Te, Bi, Pb and volatile components, is indicated for the vein-type deposit at Anomal'nyi.

In this work, we tested the equilibrium constant of hydromagnesite [Mg5(CO3)4(OH)2·4H2O] at 22.5°C proposed by Berninger et al. (2014) against field observations. By field observations we mean that analytical resultsoriginate from samples in the natural environment. In our test, we calculated saturation states of hydromagnesite, using the equilibrium constant of hydromagnesite at 22.5°C from Berninger et al., for the carbonate lakes in Qinghai-Xizang Plateau in China and for Salda Lake in Turkey,based on the hydrochemical data from literature. The predictions based on this equilibrium constant indicate that all of these lakes are strongly under-saturated with respect to hydromagnesite. However, hydromagnesite has been shown to form in all of these lakes. Therefore, this equilibrium constant is clearly in direct contradiction with field observations, leading to the conclusion that the equilibrium constant of hydromagnesite of Berninger et al. (2014) is not suitable for geochemical modelling.