Arsenohopeite, ideally Zn3(AsO4)2·4H2O, is the arsenate analogue of hopeite, Zn3(PO4)2·4H2O (it is isostructural with α-hopeite). It was found as a single colourless to blue crystalline grain from the Tsumeb mine, Namibia. The holotype specimen is ∼1 × 1 × 1 mm in size. Arsenohopeite is associated with tiny white fibres of an unidentified Zn- and As-bearing phase. It is orthorhombic, space group Pnma, with a = 10.804(2), b = 19.003(4), c = 5.112(1) Å, V = 1049.5(4) Å3 and Z = 4. Electron microprobe analysis yielded: ZnO 44.92, Fe2O3 0.92, MnO 0.51, MgO 0.20, CuO 0.02, As2O5 45.84 (wt.%). The empirical formula is (Zn2.80Fe0.06Mn0.04Mg0.03)Σ2.93(As1.01O4)2·4H2O, based on 12 oxygen atoms. Optically, the mineral is biaxial negative, with α = 1.598(2), β = 1.606(2), γ = 1.613(2) (white light) and 2Vcalc = 86°. It is not pleochroic or fluorescent. Arsenohopeite is translucent with a vitreous lustre. It is brittle, has an uneven fracture and (by analogy with hopeite) a cleavage that is perfect on {010}, good on {100} and poor on {001}. The calculated density is 3.420 g cm–3. The five strongest calculated powder diffraction lines are [d in Å (I)(hkl)]: 9.502 (100)(020), 2.926 (95)(241), 4.937 (50)(011), 4.110 (48)(230) and 3.567 (31)(240). The crystal structure of arsenohopeite has been solved by direct methods and refined in space group Pnma to R1 = 0.0353. Raman spectroscopy confirms the crystal-structure data and indicates the presence of weak hydrogen bonds.

The crystal structure of faustite, ZnAl6(PO4)4(OH)8.4H2O, was determined using single-crystal data (Mo-Kα X-radiation, CCD area detector, 1624 unique reflections, R1 = 4.91%, wR2 = 9.23%), and compared with results of a reinvestigation of the structure of its copper analogue turquoise, CuAl6(PO4)4(OH)8.4H2O (2737 unique reflections, R1 = 2.81%, wR2 = 6.90%). Both are isostructural and crystallize in space group P, with a = 7.419(2) [turquoise: 7.410(1)], b = 7.629(3) [7.633(1)], c = 9.905(3) [9.904(1)] Å, α = 69.17(2) [68.42(1)], β = 69.88(2) [69.65(1)], γ = 64.98(2) [65.05(1)]°, V = 462.2(3) [460.27(10)] Å3, and Z = 1. The structure consists of distorted MO6 polyhedra (M = Zn, Cu), AlO6 octahedra and PO4 tetrahedra. By edge- and corner-sharing of these polyhedra a fairly dense three-dimensional framework is formed which is further strengthened by a system of hydrogen bonds. The metal atoms in the unique MO6 (M = Zn or Cu) polyhedron show a distorted [2+2+2]-coordination, the distortion being more pronounced in turquoise. About 10% of the M site is vacant in both minerals. In turquoise, a previously undetected structural site with a very low occupancy of (possibly) Cu is present at the position (Ý,0,Ý).

The structure of antimonian dussertite, (AsO4)2(OH,H2O)6, has been refined in space group R3̄m with a 7.410(3), c 17.484(4) Å, Z = 3, to R = 3.2 % and Rw = 3.7 % using 377 observed reflections with I ≥ 3 σ(I). The structure is of the alunite-type and consists of sheets of corner-sharing (Fe3+,Sb5+)O6 octahedra parallel to (0001). The substitution of Sb5+ for Fe3+, and not for As5+, is unambiguously demonstrated not only by the structure refinement but also by electron microprobe analyses and crystal-chemical considerations. The icosahedrally coordinated Ba cations occupy cavities between pairs of octahedral sheets and are surrounded by six O atoms from the AsO4 tetrahedra and six O atoms from the (Fe3+,Sb5+)O6 octahedra. The mean bond lengths for the various coordination polyhedra are As-O 1.684(3) Å, (Fe,Sb)-O 2.004(1) Å, and Ba-O 2.872(2) Å. A hydrogen-bonding network is modelled using bond-valence calculations. The dussertite sample investigated is the first member of the crandallite group found to contain substantial Sb.

Decrespignyite-(Y) is a new copper yttrium rare earth carbonate chloride hydrate from the Paratoo copper mine, near Yunta, Olary district, South Australia. Decrespignyite-(Y) occurs as blue crusts, coatings and fillings in thin fissures on the slatey country rock. Individual pseudohexagonal platelets are typically 10–50 µm in maximum dimension and are often curved. Associated minerals include caysichite-(Y), donnayite-(Y), malachite and kamphaugite-(Y). Electron microprobe and CHN analyses gave: Y2O3 42.2; La2O3 0.1; Pr2O3 0.1; Nd2O3 1.3; Sm2O3 1.0; Gd2O3 4; Tb2O3 0.4; Dy2O3 3.7; Ho2O3 2.6; Er2O3 2.5; CaO 0.5; CuO 10.9; Cl 3.0; CO2 19.8; H2O 10.8, yielding an empirical formula of (Y3.08Gd0.22Dy0.16Ho0.11Er0.10Nd0.06Sm0.05Tb0.02La0.02Pr0.01Ca0.08)∑3.91Cu1.12(CO3)3.70-Cl0.7(OH)5.79·2.4H2O. The simplified formula is (Y,REE)4Cu(CO3)4Cl(OH)5·2H2O. The mineral is royal blue to turquoise-blue in colour, transparent, with a pearly to vitreous lustre and a pale blue streak. No cleavage was observed but the morphology suggests that cleavage would be on [010]. The Mohs' hardness is estimated to be 4. The strongest lines in the X-ray powder pattern are {dobs (Iobs) (hkl)} 22.79 (30) (010); 7.463 (30) (001); 7.086 (50) (011); 6.241 (100) (021); 4.216 (30) (12); 3.530 (40) (022); 3.336 (30) (032); 2.143 (30) (222, 01). The powder diffraction pattern was indexed on a monoclinic cell with a = 8.899(6), b = 22.77(2), c = 8.589(6)Å, β = 120.06(5)°, V = 1506.3(7) Å3 and Z = 4. The structure of the new mineral could not be determined but powder diffraction data indicate the space group is P2, Pm or P2/m. The measured density is 3.64(2) g/cm3 and the calculated density is 3.645 g/cm3. Decrespignyite-(Y) is biaxial negative with α = 1.604(4) and γ = 1.638(3) with β very close to γ pleochroism is medium strong; X very pale bluish, Y and Z bluish (with greenish tint). Decrespignyite-(Y) is a supergene mineral which precipitated from mildly basic carbonated ground waters. The mineral is named after Robert Champion de Crespigny, a prominent figure in the Australian mining industry and chancellor of the University of Adelaide.

The previously unknown crystal structure of the basic lead nitrate Pb2(OH)3(NO3) has been determined using single-crystal X-ray diffraction data (Mo-Kα radiation, CCD area detector). The compound is orthorhombic, space group Immm, with a = 8.314(2), b = 8.545(2), c = 17.210(3) Å (R1 = 2.78% for 940 ‘observed’ reflections with Fo > 4σ(Fo)). The layered structure contains a previously unknown cuboid [Pb8(OH)12]4+ cluster and NO3 groups. The study used crystals formed by anthropogenic processes on a medieval mine dump, probably involving black gunpowder used in the blasting of ore. Pb2(OH)3(NO3) is associated with a second nitrate, Pb13O8(OH)6(NO3)4, which was previously designated as “Pb3O3(OH)4(NO3)2” or “Pb3(OH)5(NO3)”. It is rhombohedral, space group , with a = 10.263(1), c = 25.454(5) Å, and a structure solution is in complete agreement with an independent single-crystal study by Li et al. (2001). Probable hydrogen bonds in Pb2(OH)3(NO3) are indicated. Reported data on clusters and lead hydroxide and oxide nitrates are summarized and discussed critically. The probable conditions of formation of the studied samples are evaluated.

Kapellasite, Cu3Zn(OH)6Cl2, is a new secondary mineral from the Sounion No. 19 mine, Kamariza, Lavrion, Greece. It is a polymorph of herbertsmithite. Kapellasite forms crusts and small aggregates up to 0.5 mm, composed of bladed or needle-like indistinct crystals up to 0.2 mm long. The colour is green-blue, the streak is light green-blue. There is a good cleavage parallel to ﹛0001﹜. Kapellasite is uniaxial negative, ω = 1.80(1), ε = 1.76(1); pleochroism is distinct, with E = pale green, O = green-blue. Dmeas = 3.55(10) g/cm3; Dcalc. = 3.62 g/cm3. Electron microprobe analyses of the type material gave CuO 58.86, ZnO 13.92, NiO 0.03, CoO 0.03, Fe2O3 0.04, Cl 16.70, H2O (calc.) 12.22, total 101.80, less O = Cl 3.77, total 98.03 wt.%. The empirical formula is (Cu3.24Zn0.75)Σ3.99(OH)5.94Cl2.06, based on 8 anions. The five strongest XRD lines are [d in Å (I/I0, hkl)] 5.730 (100, 001), 2.865 (11, 002), 2.730 (4, 200), 2.464 (9, 021/201), 1.976 (5, 022/202). Kapellasite is trigonal, space group Pml, unit-cell parameters (from single-crystal data) a = 6.300(1), c = 5.733(1) Å, V= 197.06(6) Å3, Z = 1. The crystal structure of kapellasite is based on brucite-like sheets parallel to (0001), built from edge-sharing distorted M(OH,Cl)6 (M = Cu, Zn) octahedra. The sheets stack directly on each other (…AAA… stacking). Bonding between adjacent sheets is only due to weak hydrogen and O…C1 bonds. The name is in honour of Christo Kapellas (1938–2004), collector and mineral dealer from Kamariza, Lavrion, Greece.

During investigations of the system Sc2O3-Al2O3-TiO2-SiO2, a new, unusual microporous compound, Cs3ScSi8O19, was synthesized as colourless plates from a CsF-MoO3 flux. The crystal structure was determined from single-crystal X-ray diffraction data (Mo-Kα radiation, CCD area detector). The compound is orthorhombic, space group Pnma, with a = 11.286(2), b = 7.033(1), c = 26.714(5) Å, and Z = 4 (R1(F) = 2.6% and wR2all(F2) = 7.3%, using 3066 ‘observed’ reflections with Fo > 4σ(Fo)). The crystal structure of Cs3ScSi8O19 represents a new microporous framework structure type (‘MCV-1’), and the compound is exceptional in being the first representative of a mixed octahedral-tetrahedral framework structure, in which the [TO4]:[MO6] ratio is >6:1. The structure is based on isolated, nearly regular ScO6 octahedra [dav(Sc—O) = 2.112 Å] sharing corners with SiO4 tetrahedra to form an open framework with four-, six- and eight-membered rings; the latter are formed by SiO4 tetrahedra only. Two fully occupied Cs positions are located in large framework voids close to the six-membered rings, whereas four partly occupied and disordered Cs positions are close to very large framework voids bordered by the puckered eight-membered rings. The cavities are linked into channels parallel to [100] and [010]. The structure is compared with that of Cs2TiSi6O15 and related microporous scandium-, REE-, titano- and zirconosilicate minerals and compounds. Cs3ScSi8O19 or derivatives may be important in the context of immobilization of radioactive 137Cs waste, cationic conductivity or catalysis.

The Paratoo copper deposit, located in the Neoproterozoic to Cambrian Adelaide Geosyncline, South Australia, produced around 360 tons of Cu between 1888 and 1967 from oxidized ores. The deposit is located in the core of a breached, doubly plunging anticline, near a zone of disruption containing brecciated Adelaidean sedimentary rocks and dolerite (‘Paratoo Diapir’), and hosted in dolomitic shales of the Neoproterozoic Burra Formation. Near the surface, the mineralization resides mainly in deeply weathered quartz-magnetite-sulphide (pyrite, chalcopyrite) veins (⩽10 cm wide). At depth, drill cores reveal disseminated magnetite, pyrite, chalcopyrite, copper sulphide and native copper associated with extensive potassic alteration. K-Na-rich fluids also affected the dolerite in the ‘Paratoo diapir’, resulting in the precipitation of K-feldspar, dravite and K-bearing chabazite-Na. The most likely scenario for the genesis of the Paratoo deposit involves circulation of basinal fluids, focusing into the ‘Paratoo Diapir’, and ore precipitation through neutralization by fluid-rock interaction with the dolomitic shales hosting the mineralization.

The Paratoo deposit is deeply weathered, with malachite and chrysocolla (± tenorite and cuprite) containing the bulk of the copper recovered from the shallow workings. A diverse assemblage of secondary REE-bearing carbonate minerals, including the new species decrespignyite-(Y) and paratooite-(La), is associated with the weathered base metal and magnetite ores. Whole-rock geochemical analyses of fresh and mineralized host rock and of vein material reveals that the mineralization is associated with a strong, albeit highly variable, enrichment in light rare earth elements (LREE). This association indicates that REE and base metals were introduced by the same hydrothermal fluid. The strong negative Ce anomaly found in secondary REE minerals and mineralized rock samples suggests an upgrade of the REE contents in the weathering zone, insoluble Ce4+ being left behind.

The Fe-oxide-REE-base metal association at Paratoo is also characteristic of the giant Mesoproterozoic Fe oxide copper gold deposit of Olympic Dam, located 350 km to the NW. A similar association is found in the Palaeozoic deposits of the Mt Painter Inlier, 300 km to the NNE. The widespread occurrence of this elemental association in the Province probably reflects the geochemistry of the basement, which contains numerous Mesoproterozoic granites enriched in REE and U.

Bariosincosite is a new barium vanadium phosphate hydrate from the Spring Creek Mine, near Wilmington, South Australia. The new mineral occurs as irregular clusters of pale green, very thin platey crystals up to 250 µm across and 2 to 5 µm thick. The tetragonal crystals are tabular on {001} and the other form present is {100}. Associated with bariosincosite are quartz, cuprite, native copper, fluorapatite, whitlockite, baryte and springcreekite, BaV33+ (PO4)2(OH,H2O)6. Bariosincosite appears to have formed under supergene or low-temperature late-stage hydrothermal conditions. Electron microprobe analysis yielded: BaO 23.20; SrO 4.19; CaO 0.36; VO2 31.55; Fe2O3 0.20; Al2O3 0.50; P2O5 28.15; H2O 13.93 (calculated). These data give an empirical formula of (Ba0.77Sr0.20Ca0.03)∑1.00[(V0.964+ Al0.03Fe0.013+)∑1.00O(PO4)]2·4H2O, calculated on the basis of two P atoms. The simplified formula is Ba(V4+OPO4)2·4H2O. The mineral is transparent with a very pale green streak, a vitreous lustre and an estimated Mohs hardness of 3. The strongest lines in the X-ray powder pattern are [dobs (Iobs) (hkl)] 6.414 (20) (110, 002); 5.748 (70) (111); 4.552 (30) (112, 200); 3.198 (20) (220, 004); 3.100 (100) (203, 221); 2.847 (40) (222, 114); 2.786 (80) (311); 2.368 (30) (313, 115); and 2.017 (100) (420, 332, 116). These data were indexed on a tetragonal cell, with a = 9.031(6), c = 12.755(8) Å and V = 1040(1) Å3; the space group is probably P4/n or P4/nmm. For Z = 4 and using the empirical formula, the calculated density is 3.306 gm/cm3. Bariosincosite is uniaxial negative with ω = 1.721(2) and ε = 1.715(2) (white light); pleochroism is weak from colourless (E) to pale green (O), absorption O > E. The mineral is named for the relationship to sincosite, Ca(V4+OPO4)2·4H2O.

Domerockite, Cu4(AsO4)2(AsO3OH)(OH)3·H2O, is a new mineral from the Dome Rock Mine, South Australia. It occurs as aggregates of bluish green, equant to short prismatic and tabular crystals up to 0.3 mm long and 0.2 mm across. Domerockite is translucent, with a vitreous lustre and pale green streak. It displays no fluorescence under UV irradiation. The mineral is brittle with an uneven fracture, a Mohs hardness of ∼3 and a calculated density of 4.44 g/cm3 (based on the structure refinement). Optically, it is biaxial negative, with α = 1.798(4), β = 1.814(4), γ = 1.817(4), 2Vcalc. = 46°; pleochroism is very weak; X pale greenish yellow, Y greenish blue, Z greenish blue; absorption X < Y = Z; orientation is uncertain. Chemical analysis by electron microprobe gave CuO 52.04, ZnO 0.78, BaO 0.11, As2O537.67, P2O50.32, SiO20.24, H2O 8.84, total 100.00 wt.%, with H2O calculated by difference. The empirical chemical formula is (Cu3.94, Zn0.06)Σ4.00H0.91(As1.97, P0.03, Si0.02)Σ2.02O8(OH)3.00˙H2O based on 12 oxygen atoms.

Domerockite is triclinic, space group P, with a = 5.378(11), b = 8.962(18) c = 9.841(2) Å, α = 75.25(3), β = 83.56(3), γ = 79.97(3)°, V = 450.5(16) Å3 and Z = 2. The eight strongest lines in the X-ray powder diffraction pattern are [d (Å), (I)(hkl)]: 4.716 (30)(101, 002, 111), 3.697 (25)(121), 3.605 (30)(120, 12), 3.119 (60)(12), 3.073 (100)(1), 2.856 (40)(02, 030), 2.464 (50)(212, 13), 2.443 (40)(014). The crystal structure of domerockite has been solved by direct methods and refined to an R index of 7.44% using 2635 observed reflections. The structure comprises [Cuφ4] (φ = O, OH) chains of edge-sharing sharing, distorted octahedra that extend along [10] and are decorated by AsO4 tetrahedra to form sheets in the (010) plane. Dimers of edge-sharing [CuO4(OH)(H2O)] octahedra share corners with dimers of edge-sharing [CuO4(OH)] square pyramids to form zigzag chains which extend along [101]. The chains lie between and link to the sheets by sharings corners of octahedra, square pyramids and tetrahedra to form a heteropolyhedral framework.

The crystal structure of ulrichite, CaCu2+(UO2)(PO4)2·4H2O (space group P21/c, a = 12.784(3), b = 6.996(1), c = 13.007(3)Å, β = 91.92(1)°, V = 1162.7(4)Å3, Z = 4) was redetermined using X-ray diffraction data measured from a twinned crystal with Mo-Kα radiation and a CCD area detector (2510 unique reflections with Fo > 4σ(Fo), R1 = 8.8%). Ulrichite crystallizes in space group P21/c rather than C2/m reported previously. The newly determined atomic positions give reasonable coordination polyhedra. One unique Ca atom is irregularly coordinated by eight O atoms (<Ca–O> = 2.46 Å). One unique U atom shows a {2+5} coordination with characteristic bond angles and lengths (1.806(11)Å, 1.842(12)Å and five bonds between 2.252(15) and 2.441(11)Å). Furthermore, the structure contains groups in which strongly elongated CuO6 ‘octahedra’ (also describable as CuO4 squares) are corner-linked to two PO4 tetrahedra via two opposite, equatorial O atoms. Edge- and corner-sharing UO7, CaO8 and PO4 polyhedra form heteropolyhedral sheets parallel to (001) that are linked to adjacent sheets via the CuO6 ‘octahedra’ and hydrogen bonds.

The previously unknown crystal structure of mckinstryite, originally described as Ag1.18Cu0.82S or (Ag,Cu)2S, was solved and refined using single-crystal X-ray diffractometer data collected from a sample from the Clara mine, Black Forest (Mo-Kα radiation, CCD area detector, R1(F) = 3.85%). Mckinstryite has the refined formula Ag4.92Cu3.08S4 or Ag1.23Cu0.77S (idealized Ag5Cu3S4 or Ag1.25Cu0.75S) and crystallizes in space group Pnma (no. 62), with a = 14.047(3) Å, b = 7.805(2) Å , c = 15.691(3) Å, V = 1720.3(7) Å3, Z = 8. The structure contains five Ag, six Cu and eight S sites in the asymmetric unit. One of the Ag sites shows minor Cu-for-Ag substitution. The topology is based on flat, interrupted (010) layers of Cu and S atoms (all atoms on y = 0.25), in which the Cu atoms show triangular or two-coordination to S (interrupted {6,3} tiling). These layers alternate with uneven layers consisting of Ag atoms showing irregular three- to two-coordination to S. Some fairly short Ag–Cu contact distances (2.781–2.884 Å) strongly indicate that metal-metal interaction plays an important role in mckinstryite. The topology is related to that of stromeyerite (∼AgCuS) which contains complete flat layers of Cu atoms triangularly coordinated to S atoms, alternating with layers of loosely packed Ag atoms.

A critical evaluation of literature data on the chemical composition and unit-cell parameters of mckinstryite confirms the presence of a small compositional range of mckinstryite which extends approximately from Ag1.18Cu0.82S to Ag1.25Cu0.75S, with the presently studied sample being fairly Agrich. The accurate limits of this range at ambient temperature are still to be determined.

Bendadaite, ideally Fe2+Fe23+ (AsO4)2(OH)2·4H2O, is a new member of the arthurite group. It was found as a weathering product of arsenopyrite on a single hand specimen from the phosphate pegmatite Bendada, central Portugal (type locality). Co-type locality is the granite pegmatite of Lavra do Almerindo (Almerindo mine), Linópolis, Divino das Laranjeiras county, Minas Gerais, Brazil. Further localities are the Veta Negra mine, Copiapó province, Chile; Oumlil-East, Bou Azzer district, Morocco; and Pira Inferida yard, Fenugu Sibiri mine, Gonnosfanadiga, Medio Campidano Province, Sardinia, Italy.

Type bendadaite occurs as blackish green to dark brownish tufts (<0.1 mm long) and flattened radiating aggregates, in intimate association with an intermediate member of the scorodite–mansfieldite series. It is monoclinic, space group P21/c, with a = 10.239(3) Å, b = 9.713(2) Å, c = 5.552(2) Å, β = 94.11(2)°, V = 550.7(2) Å3, Z = 2. Electron-microprobe analysis yielded (wt.%): CaO 0.04, MnO 0.03, CuO 0.06, ZnO 0.04, Fe2O3 (total) 43.92, Al2O3 1.15, SnO2 0.10, As2O5 43.27, P2O5 1.86, SO3 0.03. The empirical formula is (Fe2+0.52Fe3+0.32☐0.16)Σ1.00(Fe3+1.89Al0.11)Σ2.00(As1.87P0.13)Σ2.00O8(OH)2.00·4H2O based on 2(As,P) and assuming ideal 8O, 2(OH), 4H2O and complete occupancy of the ferric iron site by Fe3+ and Al. Optically, bendadaite is biaxial, positive, 2Vest. = 85±4°, 2Vcalc. = 88°, with α 1.734(3), β 1.759(3), γ 1.787(4). Pleochroism is medium strong: X pale reddish brown, Y yellowish brown, Z dark yellowish brown; absorption Z > Y > X, optical dispersion weak, r > v. Optical axis plane is parallel to (010), with X approximately parallel to a and Z nearly parallel to c. Bendadaite has vitreous to sub-adamantine luster, is translucent and non-fluorescent. It is brittle, shows irregular fracture and a good cleavage parallel to {010}. Dmeas. 3.15±0.10 g/cm3, Dcalc. 3.193 g/cm3 (for the empirical formula). The five strongest powder diffraction lines [d in Å (I)(hkl)] are 10.22 (10)(100), 7.036 (8)(110), 4.250 (5)(111), 2.865 (4)(), 4.833 (3)(020,011). The d spacings are very similar to those of its Zn analogue, ojuelaite. The crystal structure of bendadaite was solved and refined using a crystal from the co-type locality with the composition (Fe2+0.95☐0.05)Σ1.00(Fe3+1.80Al0.20)Σ2.00(As1.48P0.52)Σ2.00O8(OH)2·4H2O (R = 1.6%), and confirms an arthurite-type atomic arrangement.

Hemimorphic crystals of four M1+-M3+-diarsenates (M1+ = Li, Na; M3+ = Al, Sc, Ga) were prepared by mild hydrothermal methods (T = 493 K) at very low pH values of ~1–1.5. The crystalst ructures of all compounds were determined using single-crystal X-ray diffraction data (Mo-Kα, CCD detector, 293 K) and were found to be isotypic with gittinsite (CaZrSi2O7), and the later described synthetic compound LiFeAs2O7. Crystaldat a for LiAlAs2O7, LiScAs2O7, LiGaAs2O7 and NaScAs2O7, respectively, are: space group C2 (no. 5), a = 6.583(1), 6.790(1), 6.638(1), 6.959(1), b = 8.007(2), 8.532(2), 8.181(2), 8.712(2), c = 4.635(1), 4.845(1), 4.696(1), 4.817(1) Å, β = 104.13(3), 103.75(3), 104.01(3), 102.05(3)°, V = 236.92(9), 272.64(9), 247.43(9), 285.6(1) Å3; Z = 2. The structure models were refined anisotropically to R1(F) = 0.0152, 0.0157, 0.0144, 0.0199, respectively.

The non-centrosymmetric framework structure contains isolated As2O7 groups (in staggered configuration; As–O–As angles show a narrow range between 130.32(16) and 139.8(2)°) which share their O ligands with MO6 (M = Al, Sc, Ga) octahedra and distorted Li/NaO4 tetrahedra. The strongly distorted LiO4 tetrahedra exhibit an average Li–O bond length of 2.071 Å, but four longer Li–O bonds (between 2.781–3.042 Å) also contribute to give a reasonable bond-valence sum for the Li atoms, and reflect an effective [4+4]-coordination. The Na compound is also characterized by four short and four long Na–O bonds; the Na atom appears slightly overbonded. The average Sc–O bond length in the two Sc representatives is 2.083 and 2.097 Å.

Details of the topology and crystal chemistry are discussed in comparison with those of gittinsite and other diarsenates, and correlations are noted. A reevaluation of the geometry of As2O7 groups in 58 presently known and structurally characterized inorganic diarsenates shows a mean As–O–As angle of 124.2° (excluding 180° angles). The As–O bond lengths to the central bridging O atom are elongated to a mean value of 1.755 Å, whereas all other bond lengths are shortened (mean value 1.666 Å); the overall mean As–O bond length is 1.688 Å.

The new, non-centrosymmetric chain silicate, K2.9Rb0.1ErSi3O9, was prepared by a high-temperature flux-growth technique, and its crystal structure was determined from single-crystal X-ray intensity data (Mo-Kα, 293 K) in space P1, with a = 6.672(1), b = 6.719(1), c = 6.725(1) Å, α = 108.87(3), β = 106.72(3), γ = 107.61(3)°, V = 245.82(6) Å3, Z = 1, R(F) = 2.81%. The compound represents a novel structure type. K2.9Rb0.1ErSi3O9 is characterized by a mixed octahedral-tetrahedral framework, in which each corner of the isolated ErO6 octahedron (<Er—O> = 2.26 Å) is linked to infinite [Si3O9] chains extending approximately along [111]. This connectivity results in a microporous character with two different, narrow channels that extend parallel to [111] and [100] and host K+ cations. The atomic arrangement is strongly pseudorhombohedral. A single-crystal Raman spectrum of K2.9Rb0.1ErSi3O9 is in agreement with the low space-group symmetry. Relations to minerals and synthetic compounds based on [Si3O9] chains are discussed, revealing that the geometry of the chain in K2.9Rb0.1ErSi3O9 is similar to that in pectolite, NaCa2[HSi3O9].

Arhbarite was described in 1982 as a new copper arsenate, Cu2(OH)AsO4·6H2O, from the Arhbar mine, Morocco. Due to the very small grain size no crystallographic data other than the X-ray powder diffraction data could be given. Reinvestigation of the type material and of new finds from the El Guanaco mine, Chile, is based on Rietveld refinement of X-ray powder data, electron microprobe investigations, optical studies as well as infrared and Raman spectra. The main results are: (1) arhbarite has the ideal formula Cu2Mg(AsO4)(OH)3 with magnesium oxide as an additional constituent and (2) arhbarite is isotypic with gilmarite, Cu3(AsO4)(OH)3. Arhbarite is triclinic, space group P1 (no. 1), unit-cell parameters (type material; refined from powder data) a= 5.315(4), b= 5.978(6), c= 5.030(6)Å, α = 113.58(6), β = 97.14(7), γ = 89.30(8)°, V= 145.2(1)Å3, Z= 1. Microprobe analyses of the type material gave MgO 10.20, CuO 47.46, NiO 0.20, CoO 0.24, As2O5 33.85, SiO2 0.10, H2O 7.58 (calc.), total 99.63 wt.%. The empirical formula is Cu1.98(Mg0.88Cu0.09Ni0.01Co0.01)S0.99(AsO4)1.02(OH)2.92, based on 7 O atoms. The Chilean arhbarite shows a slightly higher Cu content than the type material; it has the formula Cu1.99(Mg0.73Cu0.25Zn0.01)∑0.99[(AsO4)1.01(SiO4)0.01]∑1.02(OH)2.92. The formal redefinition of arhbarite has been approved by the CNMMN of the IMA.

Paratooite-(La) is a new lanthanum-dominant rare-earth copper carbonate from the Paratoo copper mine, near Yunta, Olary district, South Australia. Paratooite-(La) occurs as sheaves and radiating sprays of blade-like to tabular pale blue crystals in thin fissures in a slaty country rock. Individual crystals are typically 50–200 μm in maximum dimension but <5 μm thick. Associated minerals include donnayite-(Y), kamphaugite-(Y), and bastnäsite-(La). Electron microprobe and CHN analyses gave: La2O3 26.47; Pr2O3 7.74; Nd2O3 8.15; Sm2O3 0.66; Gd2O3 0.85; Y2O3 0.72; CaO 7.57; SrO 3.15; Na2O 3.3; CuO 5.77; F 0.24; CO2 32.05; NO2 1.12; -O=F -0.10; sum 100.03, yielding an empirical formula of (La3.54Ca2.94Na2.32Nd1.05Pr1.03Sr0.66Y0.14Gd0.10Sm0.08)Σ11.86Cu1.58(C15.84N0.53)O47.76F0.24. The simplified formula is (REE ,Ca,Na,Sr)6Cu(CO3)8 or possibly REE3(Ca,Sr)2NaCu(CO3)8. The mineral is pale turquoise-blue to pale blue in colour, transparent, with a pearly to vitreous lustre and a pale blue streak. No cleavage was observed but the morphology and TEM studies indicate a cleavage parallel to ﹛100﹜. The Mohs hardness is estimated to be 4. The strongest lines in the X-ray powder pattern are [dobs (Iobs) (hkl )]: 5.047 (53) (200); 4.786 (49) (021); 3.957 (43) (220); 3.468 (43) (012, 221); 2.927 (100) (202); 2.530 (52) (241); 2.344 (22) (420,103); 2.232 (20) (421). A synchrotron powder diffraction pattern was indexed on a primitive orthorhombic cell with a = 10.0862(5), b = 12.8088(6), c = 7.2360(4) Å, V= 934.8(1) Å3 and Z = 2. The crystal structure of the new mineral could not be determined but powder diffraction data indicate the space group is probably P 222, Pmmm , P 2221 or Pmm2. The measured density is 3.68(3) g/cm3 and the calculated density is 3.78 g/cm3. Paratooite-(La) is biaxial negative with α = 1.605(3), β = 1.696(3) and γ = 1.752(2); pleochroism is medium strong; X very pale bluish, Y and Z bluish (with greenish tint) with absorption Z ≈ Y >> X. Paratooite-(La) is a supergene mineral which precipitated from mildly basic carbonated groundwaters. The mineral is named for the type locality.

Nyholmite, Cd3Zn2(AsO3OH)2(AsO4)2·4H2O, from the Block 14 Opencut, Broken Hill, New South Wales, Australia, is a new Cd-Zn arsenate species, isostructural with the minerals of the hureaulite group. The mineral occurs in a quartz-garnet-arsenopyrite matrix as white globules, tufted aggregates of fibrous crystals and radiating hemispheres of thin, colourless, bladed crystals. Associated minerals are goldquarryite, lavendulan-sampleite, scorodite-strengite and gypsum. Individual crystals are up to 0.2 mm in length and 0.05 mm across. The mineral is transparent to translucent with a vitreous lustre. It is brittle with an uneven fracture and a white streak. The Mohs hardness is 3–3.5 and the calculated density is 4.23 g cm–3 for the empirical formula. Electron microprobe analyses yielded CdO 34.58, ZnO 9.72, MnO 3.59, CuO 3.39, Al2O3 0.20, CaO 0.16, PbO 0.37, As2O5 34.55, P2O5 6.29 totalling 92.85 wt.%. The empirical formula, based on 20 oxygen atoms, is Ca0.03Pb0.02 Cd2.80Al0.04Zn1.24-Cu0.44Mn0.53[(AsO4)3.13(PO4)0.92]Σ4.05H1.91·3.79H2O. Nyholmite is monoclinic, C2/c, a = 18.062(4) Å, b = 9.341(2) Å, c = 9.844(2) Å, β = 96.17(3)°, V = 1651.2(6) Å3 (single-crystal data, at 123 K). The six strongest lines in the X-ray powder diffraction pattern are [d(Å),I,(hkl)]: 8.985,30,(200); 8.283,85,(110); 6.169,25,(111); 4.878,25,(002); 3.234,100,(2, 420); 3.079,65,(222, 511); 2.976’45’(113). The crystal structure was solved by Patterson methods and refined using 2045 observed reflections to R1(F) = 3.73%. The structure is characterized by a kinked, five-membered chain of edge-sharing Mφ6 (φ = unspecified anion) octahedra, or pentamer, that extends in the a direction. The pentamers link by sharing corners to form a sheet in the (001) plane. Pentamers are also linked, via corner-sharing, by (As,P)O4 groups forming thick slabs in the (001) plane. The slabs link in the c direction by cornersharing between octahedra and tetrahedra to form a dense heteropolyhedral framework. Moderate to weak hydrogen-bonding provides additional linkage between the slabs.

Fassinaite, ideally Pb22+(S2O3)(CO3), is a new mineral from the Trentini mine, Mount Naro, Vicenza Province, Veneto, Italy (holotype locality). It is also reported from the Erasmus adit, Schwarzleo District, Leogang, Salzburg, Austria and the Friedrich-Christian mine, Schapbach, Black Forest, Baden-Wurttemberg, Germany (cotype localities). At the Italian type locality it occurs as acicular [010]. colourless crystals up to 200 μn long, closely associated with galena, quartz and anglesite. At the Austrian cotype locality it is associated with cerussite, rare sulphur and very rare phosgenite. At the German cotype locality anglesite is the only associated phase. Fassinaite crystals commonly have flat chisel-shaped terminations. They are transparent with vitreous to adamantine lustre and a white streak. Fassinaite is brittle with an irregular fracture and no discernible cleavage; the estimated Mohs hardness is 11/2—2. The calculated density for the type material is 6.084 g cm–3 (on the basis of the empirical formula), whereas the X-ray density is 5.947 g cm–3. In common with other natural lead thiosulphates (i.e. sidpietersite and steverustite) fassinaite has intense internal reflections, which do not allow satisfactory optical data to be collected; the crystals are length-slow and have very high birefringence. The mineral is not fluorescent.

Fassinaite is orthorhombic, space group Pnma, with unit-cell parameters (for the holotype material) a = 16.320(2), b = 8.7616(6), c = 4.5809(7) Å, V = 655.0(1) Å3, a:b:c = 1.863:1:0.523, Z = 4. Single-crystal structural studies were carried out on crystals from all three localities: R1(F) values range between 0.0353 and 0.0596. The structure consists of rod-like arrangements of Pb-centred polyhedra that extend along the [010] direction. These ‘rods’ are linked, alternately, by (CO3)2– and (S2O3)2– groups. The (S2O3)2– groups point alternately left and right (in a projection on [001] with [010] set vertical) if the apex occupied by the S2– in the thiosulphate group is defined to be the atom giving the direction. The lead atoms are nine-coordinated by seven oxygen atoms and two sulphur (S2–) atoms. The eight strongest X-ray powder-diffraction lines [d in Å (I/I0) (hkl)] are: 4.410 (39) (101), 4.381 (59) (020), 4.080 (62) (400), 3.504 (75) (301), 3.108 (100) (121), 2.986 (82) (420), 2.952 (49) (221) and 2.736 (60) (321). Electron-microprobe analyses produce an empirical formula Pb2.01(1)(S1.82(2)O3)CO3 (on the basis of six oxygen atoms). The presence of both carbonate and thiosulphate groups was corroborated by Raman spectra, which are discussed in detail. Fassinaite is named after Bruno Fassina (b. 1943), an Italian mineral collector who discovered the mineral in 2009.

Hoganite, copper(II) acetate monohydrate, and paceite (pronounced ‘pace-ite’), calcium(II) copper(II) tetraacetate hexahydrate, occur as isolated crystals embedded in ferruginous gossan from the Potosi Pit, Broken Hill, New South Wales, Australia. They are associated with goethite, hematite, quartz, linarite, malachite, azurite, cerussite and cuprian smithsonite. Hoganite is bluish green with a pale blue streak and a Mohs hardness of 1½; it possesses perfect {001} and distinct {110} cleavages and has a conchoidal fracture. Chemical analysis of hoganite gave (wt.%) C 23.85; H 3.95; Cu 31.6; Fe 0.4; O (by difference) 40.2, yielding an empirical formula of C4H7.89O5.07Cu1.00Fe0.01. The simplified formula is C4H8O5Cu or Cu(CH3COO)2.H2O, the mineral being identical to the synthetic compound of the same formula. Single-crystal X-ray data for hoganite are: monoclinic, space group C2/c, a = 13.162(3), b = 8.555(2), c = 13.850(3)Å, β = 117.08(3)°, Z = 8. The density, calculated from single-crystal data, is 1.910 g cm−3. The strongest lines in the X-ray powder pattern are [dobs (Iobs) (hkl)] 6.921 (100) (011); 3.532 (28) (202); 6.176 (14) (200); 3.592 (11) (22); 5.382 (10) (11); 2.278 (10) (204); 5.872 (9) (002). Hoganite (orientation presently unknown) is biaxial positive with α = 1.533(2), β = 1.541(3), γ = 1.554(2), 2V(meas.) = 85(5)°, 2V(calc.) = 76.8°, dispersion is r < v, medium (white light); it is strongly pleochroic with X = blue, Y = pale bluish, Z = pale bluish green and absorption X > Y > Z. The mineral is named after Graham P. Hogan of Broken Hill, New South Wales, Australia, a miner and well-known collector of Broken Hill minerals.

Paceite is dark blue with a pale blue streak and a Mohs hardness of 1½; it possesses perfect {100} and {110} cleavages and has an uneven fracture. Chemical analysis of paceite gave (wt.%) C 21.25; H 5.3; Ca 9.0; Cu 14.1; O (by difference) 50.35, yielding an empirical formula of C8H23.77O14.23Ca1.02-Cu1.00. The simplified formula is C8H24O14CaCu or CaCu(CH3COO)4.6H2O, the mineral being identical to the synthetic compound of the same formula. Unit-cell data (refined from X-ray powder diffraction data) for paceite are: tetragonal, space group I4/m, a = 11.155(4), c = 16.236(17)Å, Z = 4. The density, calculated from refined cell data, is 1.472 g cm−3. The strongest lines in the X-ray powder pattern are [dobs (Iobs) (hkl)] 7.896 (100) (110); 3.530 (20) (310); 5.586 (15) (200); 8.132 (8) (002); 9.297 (6) (101); 2.497 (4) (420); 3.042 (3) (321). Paceite is uniaxial positive with ω = 1.439(2) and ɛ = 1.482(3) (white light); pleochroism is bluish with a greenish tint (O), pale bluish with a greyish tint (E), and absorption O ⩾ E. The mineral is named after Frank L. Pace of Broken Hill, New South Wales, Australia, an ex-miner and well-known collector of Broken Hill minerals.