Mn-substituted goethite was synthesized and the interaction between arsenite (As(III)) and Mn-substituted goethite was investigated by both solution chemistry and X-ray adsorption near edge structure (XANES) spectroscopy. Results indicate that the oxidation of As(III) is favored by Mn-substituted goethite. This reaction was more sensitive to temperature than to pH. Different reaction mechanisms may account for As(III) oxidation. Since As(III) is more mobile and toxic than As(V), the oxidation reaction of As(III) with Mn-substituted goethite may decrease arsenic toxicity under some conditions.

Two-line ferrihydrite is an important adsorbent of many toxics in natural and anthropogenic systems; however, the specific structural sites responsible for the high adsorption capacity are not well understood. A combination of chemical and spectroscopic techniques have been employed in this study to gain further insight into the structural nature of sites at the ferrihydrite surface. The kinetics of iron isotopic exchange demonstrated that there are at least two types of iron sites in ferrihydrite. One population of sites, referred to as labile sites, approached iron isotopic equilibrium within 24 hr in 59Fe-NTA solutions, while the second population of sites, referred to as non-labile, exhibited a much slower rate of isotopic exchange. Adsorbed arsenate reduced the degree of exchange by labile sites, indicating that the anion blocked or greatly inhibited the rate of exchange of these sites. Mössbauer spectra were collected from a variety of samples including 56Fe-ferrihydrite samples with 57Fe in labile sites, samples containing 57Fe throughout the structure, and samples with 57Fe in non-labile sites. The spectra showed characteristic broad doublets signifying poor structural order. Refined fits of the spectra indicated that labile sites have larger quadrupole splitting, hence more local distortion, than non-labile sites. In all cases, the spectra demonstrated some degree of asymmetry, indicating a distribution of Fe environments in ferrihydrite. Overall spectral findings, combined with recent EXAFS results (Waychunas et al., 1993), indicate that labile sites likely are more reactive (with respect to iron isotopic exchange) because they have fewer neighboring Fe octahedra and are therefore bound less strongly to the ferrihydrite structure. The labile population of sites probably is composed of end sites of the dioctahedral chain structure of 2-line ferrihydrite, which is a subset of the entire population of surface sites. Mössbauer spectra of samples containing adsorbed arsenate indicated that the anion may slightly decrease the distortion of labile sites and stabilized the structure as a whole by bidentate bonding.

The new mineral naalasite (IMA2023–027), NaAl(AsO3OH)2⋅H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it is a secondary alteration phase associated with anhydrite, juansilvaite, magnesiokoritnigite and a lavendulan-like phase. Naalasite occurs in tightly intergrown aggregates and druses of equant crystals. Crystals are light to medium pink and transparent, with vitreous lustre and white streak. The Mohs hardness is ~3½. The density is 3.19(2) g⋅cm–3. Optically, naalasite is uniaxial (+), with ω = 1.630(3) and ɛ = 1.660(3) (white light). The empirical formula (based on 9 O apfu) is Na0.92Al0.61Fe3+0.39As2O9H4.07. Naalasite is trigonal, space group R32, with cell parameters: a = 8.494(4), c = 26.430(13) Å, V = 1651.5(4) Å3 and Z = 9. The structure, refined to R1 = 3.78% for 641 I > 2σI reflections, is based on a loose 3D framework of alternating AsO3OH tetrahedra and AlO6 octahedra. The structure is topologically equivalent to that of nafeasite and can be regarded as its Al analogue, even though nafeasite is monoclinic with space group C2.

Montmorillonite modified with the cationic biopolymer, chitosan, has, in weak acidic solutions, protonated amine groups which act as anion-adsorption sites. Due to the specific surroundings of the adsorption sites and diffusion paths in the interlayer of chitosan-montmorillonite, preferential adsorption of certain anions is likely. In the present study, the adsorption properties for the inorganic anions Cr(VI) and As(V) were determined, taking into account solution pH and competitive adsorption in the presence of Cl− and ${\text{SO}}_4^{2-}$${\rm{SO}}_4^{2 - }$. Chitosan-montmorillonite was prepared by adding an amount of chitosan equivalent to 500% of the cation exchange capacity (CEC) at pH 5 and 75°C. The resulting anion exchange capacity was ∼0.34 molc/kg. The adsorption properties for As(V) and Cr(VI) were determined with the batch technique at pH 3 to 9. Adsorption isotherms were fitted to the Langmuir and Dubinin-Radushkevich equations and judged quantitatively by the correlation coefficient. To describe the competitive adsorption, the selectivity (S) was determined by the ratio of amounts of anions A and B adsorbed (qA/qB) in a binary system. The ionic species adsorbed, i.e. either Cr(VI) or As(V), depended on the pH, as did the degree of protonation of the amine groups, and this played a decisive role in the amount of anions adsorbed. The maximum amount of Cr(VI) adsorbed was 180 mmol/kg at pH 3.5, whereas for As(V) it was 120 mmol/kg at pH 4.0 to 5.0. The adsorption process of Cr(VI) and As(V) fit well to the Langmuir isotherm. By increasing the concentration of the competitive anion, Cl−, in solution, the amount of Cr(VI) and As(V) adsorbed remained almostconstant, whereas ${\text{SO}}_4^{2-}$${\rm{SO}}_4^{2 - }$ had a more pronounced competitive effect. At concentration ratios of 0.5 and 1 for ${\text{SO}}_4^{2-}$${\rm{SO}}_4^{2 - }$ to Cr(VI) and As(V), respectively, the sorption capacity decreased by 10 and 25%, respectively. The sequence of the selectivity was: $\text{Cr}\left(\text{VI}\right)>{\text{SO}}_4^{2-}>\text{As}\left(\text{V}\right)>{\text{Cl}}^{-}$${\rm{Cr}}\left( {{\rm{VI}}} \right) > {\rm{SO}}_4^{2 - } > {\rm{As}}\left( {\rm{V}} \right) > {\rm{C}}{{\rm{l}}^ - }$. Chitosan-montmorillonite showed a high selectivity for Cr(VI), which adsorbed chemically. Despite the lower affinity for As(V) and physical adsorption, the adsorption capacity was relatively high.

The As sorption capacity of a natural Mn and Fe mineral-containing sample from the Iron Quadrangle province, Brazil, was investigated. A detailed mineralogical identification was obtained by combining X-ray diffraction analyses (with Rietveld refinement), X-ray fluorescence spectroscopy, optical microscopy, and scanning electron microscopy coupled with X-ray energy dispersive spectrometry-EDS. The oxidation state of the adsorbed As species was determined by X-ray absorption near edge structure spectroscopy. The results demonstrate that the presence of naturally occurring Mn oxides promotes the effective oxidation of As (III) to As(V). Also, the Mn minerals show a significant uptake of both the trivalent and pentavalent As species. This study demonstrates that the combined influences of As(III) depletion by oxidation and adsorption on a natural oxide sample consisting of Mn minerals and Fe oxides may effectively contribute to the reduction the As concentration in waters.

The use of waste materials from mineral ore processing has much potential for immobilizing pollutants such as arsenic (As) in natural soils and waters. The purpose of the present study was to investigate red mud (RM, a finely textured bauxite-ore residue) as a sequestering agent for arsenate and phosphate, including characterization of the types of surface complexes formed. The mineralogical and structural changes occurring in RM were investigated after exchange with arsenate [As(V)-RM] and phosphate [P(V)-RM] anions at pH 4.0, 7.0, and 10.0. Eight different phases were present in the untreated red mud (RMnt), though 80 wt.% of the crystalline phase consisted of sodalite, hematite, gibbsite, and boehmite. The X-ray diffraction (XRD) data for As(V)-RM revealed an anion-promoted dissolution of the gibbsite, suggesting that this phase was the most active for As(V) sequestration. In addition, the lattice parameters of cancrinite were different in As(V)-RM at pH 7.0 and 10.0 from those in RMnt. The changes may be related to the incorporation of arsenate in the cancrinite cages. X-ray diffraction patterns of P(V)-RM at pH 4.0 and 7.0 revealed the dissolution of sodalite, hematite, and gibbsite, and the formation of a novel phase, berlinite [(α,β)AlPO4]. The new phases detected through XRD and thermal (TG/DTG) analysis in P(V)-RM probably originated through an initial phosphate-promoted dissolution of some RM phases, followed by a precipitation reaction between the phosphate and Al/Fe ions. The results obtained suggest that phosphate and arsenate, though with different reactivities, were strongly bound to some RM phases, such as gibbsite, cancrinite, sodalite, and hematite through mechanisms such as chemical sorption and coprecipitation reactions. The knowledge acquired will be helpful in selecting alternative materials such as red muds, which currently pose critical economic and environmental challenges related to their disposal, for the decontamination of soils and waters polluted with As.

A new occurrence of austinite, CaZnAsO4(OH), conichalcite, CaCuAsO4(OH), and zincolivenite, CuZnAsO4(OH), is described from the Tripi mine, Peloritani Mountains, Sicily, Italy. These species have been observed in euhedral crystals in vugs of a calcite vein and were characterised using single-crystal X-ray diffraction, electron microprobe analysis and micro-Raman spectroscopy. Austinite and conichalcite have isotypic relations, both crystallising in space group P212121. Unit-cell parameters of austinite are a = 7.4931(5), b = 9.0256(6), c = 5.9155(4) Å, V = 400.06(5) Å3; its crystal structure was refined on the basis of 1210 unique reflections with Fo > 4σ(Fo) and 77 least-square parameters to R1 = 0.0236. Conichalcite has unit-cell parameters a = 7.419(10), b = 9.111(11), c = 5.867(7) Å and V = 396.6(1.4) Å3; the diffraction quality of its available grains was not good enough to allow a high-quality structural refinement. Chemical formulae of austinite and conichalcite are Ca1.04(1)Zn0.86(4)Cu0.09(4)As0.98(2)P0.02(1)O4(OH)0.98 and Ca0.98(1)Fe2+0.02(4)Cu0.69(10)Zn0.30(6)As0.97(2)P0.03(1)O4(OH)0.98, respectively. The new chemical data on the austinite–conichalcite isotypic pair, coupled with previous analyses, supports a possible miscibility gap between the compositions (Zn0.25Cu0.75) and (Zn0.50Cu0.50). Zincolivenite has unit-cell parameters a = 8.4594(9), b = 8.5324(8), c = 5.9893(6) Å, V = 432.30(12) Å3 and space group Pnnm; its crystal structure was refined to R1 = 0.0230 for 523 unique reflections with Fo > 4σ(Fo) and 47 least-square parameters. Its chemical composition is Cu0.73(5)Zn1.25(5)As1.01(1)O4(OH)1.01. The refinement of the crystal structure supports the ordering of Cu and Zn in two different crystallographic sites. Micro-Raman spectra of austinite, conichalcite and zincolivenite are discussed, with a focus on the O–H stretching region where local Zn and Cu arrangements affect the position of Raman bands in zincolivenite. These arsenates probably play an environmental role in the Peloritani area, where the occurrence of high contents of some potentially toxic elements in soils and stream sediments has been reported.

The new mineral alumolukrahnite (IMA2022–059), CaCu2+Al(AsO4)2(OH)(H2O), was found at the Jote mine, Copiapó Province, Chile, where it is a secondary alteration phase associated with conichalcite, coronadite, gypsum, olivenite, pharmacosiderite, rruffite and scorodite. Alumolukrahnite occurs as crude diamond-shaped tablets up to ~0.1 mm, intergrown in crude spherical aggregates. Crystals are apple green and transparent to translucent, with vitreous lustre and a white streak. The Mohs hardness is 3½. The mineral is brittle with irregular fracture and no cleavage. The calculated density is 4.094 g cm–3. Optically, alumolukrahnite is biaxial (+) with α = 1.73(1), β = 1.74(1) and γ = 1.76(1) (white light). The empirical formula, determined from electron microprobe analyses, is Ca1.01(Cu0.92Zn0.13)Σ1.05(Al0.96Fe0.01)Σ0.97(As0.985O4)2(OH)0.88(H2O)1.12. Alumolukrahnite is triclinic, P$\bar{1}$, a = 5.343(5), b = 5.501(5), c = 7.329(5) Å, α = 67.72(2), β = 69.06(2), γ = 69.42(2)°, V = 180.3(3) Å3 and Z = 1. Alumolukrahnite is a member of the tsumcorite group and is the Al analogue of lukrahnite.

The new alluaudite-group mineral khrenovite with the ideal, end-member formula Na3Fe3+2(AsO4)3 was found in the Arsenatnaya fumarole, Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with aphthitalite-group sulfates, badalovite, calciojohillerite, nickenichite, johillerite, tilasite, svabite, achyrophanite, ozerovaite, pansnerite, arsenatrotitanite, anhydrite, sanidine, hematite, cassiterite, rutile and pseudobrookite. Khrenovite occurs as coarse prismatic crystals up to 0.2 × 0.3 × 0.8 mm and their clusters up to 1 mm across. It is transparent, honey-coloured, red-, orange- or yellow-brown, with vitreous lustre. Khrenovite is brittle, cleavage was not observed. Dcalc is 4.257 g cm–3. Khrenovite is optically biaxial (+), α = 1.825(7), β = 1.834(7), γ = 1.845(7) and 2Vmeas. = 80(10)°. The chemical composition (wt.%, electron-microprobe) is: Na2O 11.47, K2O 1.23, CaO 0.18, MgO 0.01, MnO 4.10, CuO 4.27, ZnO 1.99, Al2O3 0.17, Fe2O3 21.12, SiO2 0.08, P2O5 0.01, V2O5 0.10, As2O5 56.03, SO3 0.02, total 100.78. The empirical formula calculated on the basis of 12 O apfu is (Na2.26K0.16Ca0.02Mn0.35Cu0.33Zn0.15Al0.02Fe3+1.62)Σ4.91(As2.98Si0.01V0.01)Σ3.00O12. Khrenovite is monoclinic, C2/c, a = 12.2394(7), b = 12.7967(5), c = 6.6589(4) Å, β = 112.953(7)°, V = 960.37(10) Å3 and Z = 4. The crystal structure was solved from single-crystal X-ray diffraction data with R1 = 0.0287. Khrenovite is isostructural with other alluaudite-group minerals. Its structural formula simplified to the species-defining constituents is A(1)NaA(2)’NaM(1)NaM(2)Fe3+2(TAsO4)3. The mineral is named in honour of the Russian volcanologist and geologist Anatoly Petrovich Khrenov (1946–2016).

The new mineral nafeasite (IMA2021-103), NaFe3+(AsO3OH)2⋅H2O, was found at the Torrecillas mine, Iquique Province, Chile, where it is a secondary alteration phase associated with anhydrite, gypsum, halite, lavendulan, magnesiokoritnigite and natrojarosite. Nafeasite occurs in tightly intergrown aggregates of equant crystals. Crystals are light to medium pink and transparent, with vitreous lustre and white streak. The Mohs hardness is ~2½. The density is 3.23(2) g⋅cm–3. Optically, nafeasite is biaxial (+), with α = 1.679(3), β = 1.682(3), γ = 1.730(5) (white light); 2V = 27(2)°; and slight r < v dispersion. The empirical formulae of the holotype and cotype (based on 9 O atoms per formula unit) are Na0.98K0.02Fe0.92Al0.07As2.00O9H4.01 and Na0.97Fe0.68Al0.33As2.00O9H4.01, respectively. Nafeasite is monoclinic, space group C2, with cell parameters: a = 18.6876(16), b = 8.6769(7), c = 14.8100(10) Å, β = 105.238 (5)°, V = 2317.0(3) Å3 and Z = 12. The structure, refined to R1 = 5.03% for 5979 Io > 2σI reflections, is based on a loose 3D framework of alternating AsO3OH tetrahedra and Fe3+O6 octahedra.

The new alluaudite-group mineral paraberzeliite was found in the Arsenatnaya fumarole, Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. In the deepest zone of Arsenatnaya, paraberzeliite (holotype) is associated with anhydrite, diopside, hematite, svabite, berzeliite, schäferite, calciojohillerite, magnesioferrite, ludwigite, fluorapatite, powellite, baryte, and rhabdoborite-group and aphthitalite-group members. In the middle zone of the fumarole, paraberzeliite occurs with hematite, calciojohillerite, badalovite, johillerite, nickenichite, tilasite, svabite, fluorophlogopite, sanidine, cassiterite, anhydrite, metathénardite and belomarinaite. Paraberzeliite forms prismatic crystals up to 0.2 mm × 0.2 mm × 1 mm often occurring in open-work aggregates. It is transparent, brown (from light to dark brown, sometimes with purple or red hue) or green (from pale greenish to yellow–green). The mineral is brittle, cleavage was not observed. The Mohs hardness is 3½. Dcalc is 3.811 g cm–3. Paraberzeliite is optically biaxial (+), α = 1.718(4), β = 1.728(4), γ = 1.742(4) and 2Vmeas. = 85(5)°. The chemical composition (wt.%, electron-microprobe; holotype) is: Na2O 6.43, CaO 16.65, MgO 11.64, MnO 1.65, CuO 0.06, Fe2O3 2.45, V2O5 1.10, As2O5 59.46, total 99.44. The calculated empirical formula based on 12 O atoms per formula unit is (Na1.20Ca1.71Mg1.66Mn0.13Fe3+0.18)Σ4.88(As2.98V0.07)Σ3.05O12. Paraberzeliite is monoclinic, C2/c, a = 12.3143(7), b = 13.0679(5), c = 6.7717(4) Å, β = 113.657(7)°, V = 998.14(10) Å3 and Z = 4. The crystal structure was solved from single-crystal X-ray diffraction data, R = 0.0349. Paraberzeliite is isostructural with other alluaudite-group minerals. Its simplified crystal chemical formula is A(1)CaA(2)'NaM(1)CaM(2)Mg2(TAsO4)3. The idealised formula is NaCa2Mg2(AsO4)3, or, according to the actual nomenclature of alluaudite-group arsenates, NaCaCaMg2(AsO4)3. The name paraberzeliite reflects the dimorphism of this alluaudite-group mineral with the arsenate garnet berzeliite, ideally (Ca2Na)Mg2(AsO4)3.

The new alluaudite-group mineral calciojohillerite is one of the major arsenates in sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. In middle zones of the fumarole, calciojohillerite is associated with hematite, tenorite, johillerite, nickenichite, bradaczekite, badalovite, tilasite, lammerite, ericlaxmanite, aphthitalite-group sulfates, langbeinite, calciolangbeinite, anhydrite, sanidine, fluorophlogopite, fluoborite, cassiterite, pseudobrookite, rutile, sylvite and halite. In deep zones it occurs in association with anhydrite, diopside, hematite, svabite, berzeliite, schäferite, forsterite, magnesioferrite, ludwigite, rhabdoborite-group fluoroborates, powellite, baryte, fluorapatite, udinaite, arsenudinaite and paraberzeliite. Calciojohillerite forms prismatic crystals up to 1 cm long, their aggregates and crystal crusts up to 0.5 m2. It is transparent, colourless, pale green, pale yellow, light blue, pale lilac or pink, with vitreous lustre. The mineral is brittle, with imperfect cleavage. The Mohs hardness is 3½. Dcalc is 3.915 g cm–3. Calciojohillerite is optically biaxial (–), α = 1.719(3), β = γ = 1.732(3); 2Vmeas. = 15(10)°. Chemical composition (wt.%, electron-microprobe; holotype) is: Na2O 7.32, K2O 0.10, CaO 6.82, MgO 20.31, MnO 0.68, CuO 0.27, ZnO 0.02, Al2O3 0.56, Fe2O3 3.53, TiO2 0.01, SiO2 0.03, P2O5 1.25, V2O5 0.10, As2O5 58.77, SO3 0.13, total 99.90. The empirical formula based on 12 O atoms is (Na1.30K0.01Ca0.67Mg2.78Mn0.05Cu0.02Al0.06Fe3+0.24)Σ5.13(As2.83P0.10S0.01V0.01)Σ2.95O12. Calciojohillerite is monoclinic, C2/c, a = 11.8405(3), b = 12.7836(2), c = 6.69165(16) Å, β = 112.425(3)°, V = 936.29(4) Å3 and Z = 4. The crystal structure was solved from single-crystal X-ray diffraction data, R1 = 0.0227. Calciojohillerite is isostructural with other alluaudite-group minerals. Its simplified crystal chemical formula is A(1)CaA(1)′□A(2)□A(2)′NaM(1)MgM(2)Mg2(AsO4)3 (□ = vacancy). The idealised formula is NaCaMg3(AsO4)3, or, according to the nomenclature of alluaudite-group arsenates, NaCaMgMg2(AsO4)3. Calciojohillerite is named as an analogue of johillerite NaCu2+MgMg2(AsO4)3 with species-defining Ca instead of Cu in the ideal formula.

Jeankempite, Ca5(AsO4)2(AsO3OH)2(H2O)7, is a new mineral species (IMA2018-090) discovered amongst coatings of arsenate minerals on oxidised copper arsenides from the Mohawk No. 2 mine, Mohawk, Keweenaw County, Michigan, USA. The new mineral occurs as lamellar bundles of colourless to white plates up to 1 mm wide and is visually indistinguishable from guérinite, with which it forms intergrowths. Jeankempite is transparent to translucent with a waxy lustre and white streak, is non-fluorescent under longwave and shortwave ultraviolet illumination, has a Mohs hardness of ~1.5 and brittle tenacity with uneven fracture. Crystals are flattened on {01$\bar{1}$} and exhibit perfect cleavage on {01$\bar{1}$}. Optically, jeankempite is biaxial (+), α = 1.601(2), β = 1.607(2), γ = 1.619(2) (white light); 2Vmeas. = 72(2)° and 2Vcalc. = 71.0°. The empirical formula is (Ca4.97Na0.013Mg0.017)(As3.99S0.01)4O23H16, based on 23 O and 16 H atoms per formula unit. Thermogravimetric analysis indicates that jeankempite undergoes four weight losses totalling 16.82%, close to the expected loss of 16.30%, corresponding to eight H2O. Jeankempite is triclinic, P$\bar{1}$, a = 6.710(6), b = 14.901(14), c = 15.940(15) Å, α = 73.583(12)°, β = 81.984(12)°, γ = 82.754(12)°, V = 1507(2) Å3 and Z = 3. The final structure was refined to R1 = 0.0591 for 2781 reflections with Iobs > 3σI. The crystal structure of jeankempite is built from a network of edge- and vertex-sharing CaO6, CaO7 and AsO4 polyhedra, and we hypothesise that the new mineral has formed due to a topotactic reaction brought on by dehydration of preexisting guérinite.

The new alluaudite-group mineral badalovite was found in the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with hematite, tenorite, cassiterite, johillerite, nickenichite, calciojohillerite, bradaczekite, metathénardite, aphthitalite, langbeinite, calciolangbeinite, sanidine, fluorophlogopite, fluoborite, tilasite, anhydrite, pseudobrookite, sylvite, halite, lammerite, urusovite, ericlaxmanite, arsmirandite, svabite, krasheninnikovite, euchlorine, wulffite and alumoklyuchevskite. Badalovite forms oblique-angled prismatic crystals up to 1 mm × 1 mm × 5 mm, typically combined in groups or crusts up to several hundred cm2 in area. The mineral is transparent, green, grey, yellow or colourless, with vitreous lustre. It is brittle, the Mohs hardness is 3½. Cleavage was not observed, the fracture is uneven. Dcalc is 4.02 g cm–3. Badalovite is optically biaxial (–), α = 1.753(3), β = 1.757(3), γ = 1.758(3) and 2Vmeas. = 50(10)°. Chemical composition (wt.%, electron-microprobe; holotype) is: Na2O 9.23, K2O 0.19, CaO 2.04, MgO 13.78, MnO 0.31, CuO 0.12, ZnO 0.24, Al2O3 0.06, Fe2O3 12.77, TiO2 0.01, SiO2 0.06, P2O5 0.33, V2O5 0.05, As2O5 61.51, SO3 0.02, total 100.72. The empirical formula based on 12 O apfu is Na1.67Ca0.20K0.02Mg1.92Zn0.02Mn0.02Cu0.01Fe3+0.90Al0.01(As3.01P0.03Si0.01)Σ3.05O12. The simplified formula is Na2Mg2Fe3+(AsO4)3. Badalovite is monoclinic, C2/c, a = 11.9034(3), b = 12.7832(2), c = 6.66340(16) Å, β = 112.523(3)°, V = 936.59(4) Å3 and Z = 4. The strongest reflections of the powder XRD pattern [d,Å(I)(hkl)] are: 6.41(38)(020), 5.505(20)(200), 3.577(23)($\bar{1}$31), 3.523(25)(310), 3.211(46)($\bar{1}$12), 2.911(28)($\bar{2}$22, $\bar{3}$12), 2.765(100)(240, 400) and 2.618(26)($\bar{1}$32). The crystal structure was solved from single-crystal XRD data with an R1 of = 2.49%. Badalovite is isostructural with other alluaudite-group minerals. Its simplified crystal chemical formula is A(1)NaA(1)’□A(2) □A(2)’NaM(1)MgM(2)(Mg0.5Fe3+0.5)2(AsO4)3 (□ – vacancy) and the end-member formula is NaNaMg(MgFe3+)(AsO4)3. The mineral is named in honour of the outstanding mineralogist and geochemist Stepan Tigranovich Badalov (1919–2014).

Two new isostructural minerals edtollite K2NaCu5Fe3+O2(AsO4)4 and alumoedtollite K2NaCu5AlO2(AsO4)4 have been found in the Arsenatnaya fumarole, Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. They are associated with sylvite, tenorite, dmisokolovite, shchurovskyite, johillerite, bradaczekite, and orthoclase. Edtollite forms prismatic crystals up to 0.02 mm × 0.1 mm; alumoedtollite forms long-prismatic crystals up to 0.01 mm × 0.1 mm. Both minerals have a semi-metallic lustre. Edtollite is brown–black to black and alumoedtollite is bronze coloured. Dcalc. = 4.26 (edtollite) and 4.28 (alumoedtollite) g cm–3. In reflected light, both minerals are grey, with distinct anisotropy. Reflectance values [edtollite/alumoedtollite: R1–R2, % (λ, nm)] are: 8.3–8.2/8.7–7.7 (470); 7.7–7.4/8.3–7.4 (546); 7.1–6.9/8.3–7.4 (589); and 6.3–6.3/7.6–7.2 (650). Chemical data are: (edtollite/alumoedtollite, wt.%, electron-microprobe): Na2O 3.13/2.58, K2O 8.12/9.09, Rb2O 0.00/0.11, CaO 0.00/0.52, CuO 36.55/38.35, ZnO 0.46/0.00, Al2O3 0.00/3.48, Fe2O3 7.34/1.79, TiO2 0.27/0.00, As2O5 43.57/43.66, total 99.44/99.58. The empirical formulae, based on 18 O apfu, for edtollite is: K1.83Na1.07Cu4.88Zn0.06Fe3+0.98Ti0.04As4.03O18; and for alumoedtollite is: K2.02Rb0.01Na0.87Ca0.10Cu5.06Al0.72Fe3+0.24As3.99O18. Both minerals are triclinic, P$\bar{1}$; unit-cell parameters (edtollite/alumoedtollite) are: a = 5.1168(6)/5.0904(11), b = 9.1241(12)/9.0778(14), c = 9.6979(14)/9.6658(2) Å, α = 110.117(13)/110.334(17), β = 102.454(12)/102.461(19), γ = 92.852(11)/92.788(15)°, V = 411.32(9)/404.88(14) Å3 and Z = 1/1. The strongest reflections in the powder X-ray diffraction pattern [d,Å(I)(hkl)] are for edtollite: 8.79(92)(001), 7.63(41)(0$\bar{1}$1), 5.22(44)(011), 3.427(100)(012), 3.148(64)(0$\bar{1}$3), 2.851(65)($\bar{1}$03) and 2.551(40)($\bar{2}$01); and for alumoedtollite: 8.78(81)(001), 7.62(67)(0$\bar{1}$1), 3.418(100)(012), 3.147(52)(0$\bar{1}$3), 2.558(58)($\bar{1}$22), 2.544(65)($\bar{2}$01) and 2.528(52)($\bar{1}\bar{3}$2). The crystal structures [single-crystal X-ray diffraction, R = 0.0773 (edtollite) and 0.0826 (alumoedtollite); 1504 and 1046 unique reflections, respectively] represent a novel structure type. It is based upon a heteropolyhedral pseudo-framework with the column formed by Cu2+-centred octahedra and square pyramids, octahedra MO6 (M = Fe3+, Al3+ or Cu2+) and AsO4 tetrahedra as the main building unit. K+ and Na+ are located in wide and narrow channels, respectively. Edtollite is named after the Russian geologist and Arctic explorer Eduard Vasilievich Toll (1858–1902), alumoedtollite is its analogue with Al prevailing among trivalent cations.

A new mineral, yurmarinite, Na7(Fe3+,Mg,Cu)4(AsO4)6, occurs in sublimates of the Arsenatnaya fumarole at the Second scoria cone of the Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia. It is associated with hatertite, bradaczekite, johillerite, hematite, tenorite, tilasite and aphthitalite. Yurmarinite occurs as well-shaped, equant crystals up to 0.3 mm in size, their clusters up to 0.5 mm and thin, interrupted crystal crusts up to 3 mm × 3 mm on volcanic scoria. Crystal forms are {101}, {011}, {100}, {110} and {001}. Yurmarinite is transparent, pale green or pale yellowish green to colourless. The lustre is vitreous and the mineral is brittle. The Mohs hardness is ∼4½. One direction of imperfect cleavage was observed, the fracture is uneven. D (calc.) is 4.00 g cm−3. Yurmarinite is optically uniaxial (−), ω = 1.748(5), ε = 1.720(3). The Raman spectrum is given. The chemical composition (wt.%, electron microprobe data) is Na2O 16.85, K2O 0.97, CaO 1.28, MgO 2.33, MnO 0.05, CuO 3.17, ZnO 0.97, Al2O3 0.99, Fe2O3 16.44, TiO2 0.06, P2O5 0.12, V2O5 0.08, As2O5 56.68, total 99.89. The empirical formula, calculated on the basis of 24 O atoms per formula unit, is (Na6.55Ca0.28K0.22)S7.05(Fe2.48 3+Mg0.70Cu0.48Al0.23Zn0.14Ti0.01Mn0.01)S4.05(As5.94P0.02V0.01)S5.97O24. Yurmarinite is rhombohedral, R c, a = 13.7444(2), c = 18.3077(3) Å, V = 2995.13(8) Å3, Z = 6. The strongest reflections in the X-ray powder pattern [d, Å (I)(hkl)] are: 7.28(45)(012); 4.375(33)(211); 3.440(35)(220); 3.217(36)(131,214); 2.999(30)(223); 2.841(100)(125); 2.598(43)(410). The crystal structure was solved from single-crystal X-ray diffraction data to R = 0.0230. The structure is based on a 3D heteropolyhedral framework formed by M 4O18 clusters (M = Fe3+ > Mg,Cu) linked with AsO4 tetrahedra. Sodium atoms occupy two octahedrally coordinated sites in the voids of the framework. In terms of structure, yurmarinite is unique among minerals but isotypic with several synthetic compounds with the general formula (Na7–x ☐x )(M 3+x 3+ M 1–x 2+)(T 5+O4)2 in which T = As or P, M 3+ = Fe or Al, M 2+ = Fe and 0 ≤ x ≤ 1. The mineral is named in honour of the Russian mineralogist, petrologist and specialist in studies of ore deposits, Professor Yuriy B. Marin (b. 1939). The paper also contains a description of the Arsenathaya fumarole and an overview of arsenate minerals formed in volcanic exhalations.

Joteite (IMA2012-091), Ca2CuAl[AsO4][AsO3(OH)]2(OH)2·5H2O, is a new mineral from the Jote mine, Tierra Amarilla, Copiapó Province, Atacama, Chile. The mineral is a late-stage, low-temperature, secondary mineral occurring with conichalcite, mansfieldite, pharmacoalumite, pharmacosiderite and scorodite in narrow seams and vughs in the oxidized upper portion of a hydrothermal sulfide vein hosted by volcanoclastic rocks. Crystals occur as sky-blue to greenish-blue thin blades, flattened and twinned on {001}, up to ~300 μm in length, and exhibiting the forms {001}, {010}, {10}, {20} and {111}. The blades are commonly intergrown in wheat-sheaf-like bundles, less commonly in sprays, and sometimes aggregated as dense crusts and cavity linings. The mineral is transparent and has a very pale blue streak and vitreous lustre. The Mohs hardness is estimated at 2 to 3, the tenacity is brittle, and the fracture is curved. It has one perfect cleavage on {001}. The calculated density based on the empirical formula is 3.056 g/cm3. It is optically biaxial (–) with α = 1.634(1), β = 1.644(1), γ = 1.651(1) (white light), 2Vmeas = 78(2)° and 2Vcalc = 79.4°. The mineral exhibits weak dispersion, r < v. The optical orientation is X ≈ c*; Y ≈ b*. The pleochroism is Z (greenish blue) > Y (pale greenish blue) > X (colourless). The normalized electron-microprobe analyses (average of 5) provided: CaO 15.70, CuO 11.22, Al2O38.32, As2O546.62, H2O 18.14 (structure), total 100 wt.%. The empirical formula (based on 19 O a.p.f.u.) is: Ca1.98Cu1.00Al1.15As2.87H14.24O19. The mineral is slowly soluble in cold, concentrated HCl. Joteite is triclinic, P, with the cell parameters: a = 6.0530(2), b = 10.2329(3), c = 12.9112(4) Å, α = 87.572(2), β = 78.480(2), γ = 78.697(2)°, V = 768.40(4) Å3 and Z = 2. The eight strongest lines in the X-ray powder diffraction pattern are [dobs Å (I)(hkl)]: 12.76(100)(001), 5.009(23)(020), 4.206(26)(120,003,121), 3.92(24)(022,02,02), 3.40(25)(13), 3.233(19)(031,023,123,03), 2.97(132,201) and 2.91(15)(22,13). In the structure of joteite (R1 = 7.72% for 6003 Fo > 4σF), AsO4 and AsO3 (OH) tetrahedra, AlO6 octahedra and Cu2+O5 square pyramids share corners to form sheets parallel to {001}. In addition, 7- and 8-coordinate Ca polyhedra link to the periphery of the sheets yielding thick slabs. Between the slabs are unconnected AsO3(OH) tetrahedra, which link the slabs only via hydrogen bonding. The Raman spectrum shows features consistent with OH and/or H2O in multiple structural environments. The region between the slabs may host excess Al in place of some As.

Davidlloydite, ideally Zn3(AsO4)2(H2O)4, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as elongated prisms (∼10:1 length-to-width ratio) that are flattened on {010}, and up to 100 × 20 × 10 μm in size. The crystals occur as aggregates (up to 500 μm across) of subparallel to slightly diverging prisms lying partly on and partly embedded in fine-grained calcioandyrobertsite. Crystals are prismatic along [001] and flattened on {010}, and show the forms {010} dominant and {100} subsidiary. Davidlloydite is colourless with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. The cleavage is distinct on {010}, and no parting or twinning was observed. The Mohs hardness is 3 – 4. Davidlloydite is brittle with an irregular to hackly fracture. The calculated density is 3.661 g cm–3. Optical properties were measured with a Bloss spindle stage for the wavelength 590 nm using a gel filter. The indices of refraction are α = 1.671, β = 1.687, γ = 1.695, all ±0.002; the calculated birefringence is 0.024; 2Vobs = 65.4(6)°, 2Vcalc = 70°; the dispersion is r < v, weak; pleochroism was not observed. Davidlloydite is triclinic, space group P1, with a = 5.9756(4), b = 7.6002(5), c = 5.4471(4) Å, α = 84.2892(9), β = 90.4920(9), γ = 87.9958(9)°, V = 245.99(5) Å3, Z = 1 and a:b:c = 0.7861:1:0.7167. The seven strongest lines in the X-ray powder diffraction pattern [listed as d (Å), I, (hkl)] are as follows: 4.620, 100, (011, 10); 7.526, 71, (010); 2.974, 49, (200, 01); 3.253, 40, (021, 120); 2.701, 39, (10, 002, 1); 5.409, 37, (001); 2.810, 37, (210). Chemical analysis by electron microprobe gave As2O5 43.03, ZnO 37.95, CuO 5.65, H2O(calc) 13.27, sum 99.90 wt.%. The H2O content and the valence state of As were determined by crystal structure analysis. On the basis of 12 anions with H2O = 4 a.p.f.u., the empirical formula is (Zn2.53Cu0.39)Σ2.92As2.03O8(H2O)4.

The crystal structure of davidlloydite was solved by direct methods and refined to an R1 index of 1.51% based on 1422 unique observed reflections collected on a three-circle rotating-anode (MoKα radiation) diffractometer equipped with multilayer optics and an APEX-II detector. In the structure of davidlloydite, sheets of corner-sharing (As5+O4) and (ZnO4) tetrahedra are linked by ZnO2(H2O)4 octahedra. The structure is related to that of parahopeite.

The crystal structure of mawbyite, PbFe2(AsO4)2(OH)2 has been refined. The mineral is monoclinic, C2/m with a = 9.066(4), b = 6.286(3) c = 7.564(3) Å, β = 114.857(5)°, Z = 2; the structure has been refined to a conventional R = 4.3% using 361 observed reflections [I> 3σ(I)]. The structure contains chains of edgesharing Fe(O,OH)6 octahedra which are linked by AsO4 tetrahedra and Pb atoms in distorted square antiprismatic co-ordination. The hydrogen bonding network in the structure has been modelled using bond valence calculations. Mawbyite is confirmed to be isostructural with tsumcorite and dimorphous with carminite and the relationship between these two structures is discussed.

The new mineral species grandaite, ideally Sr2Al(AsO4)2(OH), has been discovered on the dump of Valletta mine, Maira Valley, Cuneo province, Piedmont, Italy. Its origin is related to the reaction between the ore minerals and hydrothermal solutions. It occurs in thin masses of bright orange to salmon to brown coloured crystals, or infrequently as fan-like aggregates of small (<1 mm) crystals, with reddish-brown streak and waxy to vitreous lustre. Grandaite is associated with aegirine, baryte, braunite, hematite, tilasite, quartz, unidentified Mn oxides and Mn silicates under study.

Grandaite is biaxial (+) with refractive indices α = 1.726(1), β = 1.731(1), γ = 1.752(1). Its calculated density is 4.378 g/cm3. Grandaite is monoclinic, space group P21/m, with a = 7.5764(5), b = 5.9507(4), c = 8.8050(6) Å, β = 112.551(2)°, V = 366.62(4) Å3 and Z = 2. The eight strongest diffraction lines of the observed X-ray powder diffraction pattern are [d in Å, (I), (hkl)]: 3.194 (100)(11), 2.981 (50.9)(020), 2.922 (40.2)(03), 2.743 (31.4)(120), 2.705 (65.2)(112), 2.087 (51.8) (23), 1.685 (24.5)(321), 1.663 (27.7)(132). Chemical analyses by electron microprobe gave (wt.%) SrO 29.81, CaO 7.28, BaO 1.56, Al2O3 7.07, Fe2O3 2.34, Mn2O3 1.88, MgO 1.04, PbO 0.43, As2O5 44.95, V2O5 0.50, P2O5 0.09, sum 96.95; H2O 1.83 wt.% was calculated by stoichiometry from the results of the crystal-structure analysis. Raman and infrared spectroscopies confirmed the presence of (AsO4)3− and OH groups. The empirical formula calculated on the basis of 9 O a.p.f.u., in agreement with the structural results, is (Sr1.41Ca0.64Ba0.05Pb0.01)∑=2.11(Al0.68Fe0.143+Mn0.123+Mg0.13)∑=1.07 [(As0.96V0.01)∑=0.97O4]2(OH), the simplified formula is (Sr,Ca)2(Al,Fe3+)(AsO4)2(OH) and the ideal formula is Sr2Al(AsO4)2(OH).

The crystal structure was solved by direct methods and found to be topologically identical to that of arsenbrackebuschite. The structure model was refined on the basis of 1442 observed reflections to R1 = 2.78%. In the structure of grandaite, chains of edge-sharing M3+ octahedra run along [010] and share vertices with T5+ tetrahedra, building up [M3+(T5+O4)2(OH, H2O)] units, which are connected through interstitial divalent cations. Grandaite is named after the informal appellation of the province where the type locality is located. The new mineral was approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2013-059). The discovery of grandaite and of other members of the group (description still in progress) opens up the possibility of exploring the crystal chemistry of the brackebuschite supergroup.