New compositional and structural data validate the status of jamborite

Jamborite was originally described with the formula (Ni2+,Ni3+,Fe)(OH)2(OH,S,H2O) from Ca' de' Ladri and Monteacuto Ragazza near Bologna, and Castelluccio di Moscheda near Modena, Italy. Re-examination of the mineral from the type localities and Rio Vesale, Sestola, Val Panaro (Emilia-Romagna, Italy), led to the discovery of a crystal suitable for study by single-crystal and powder X-ray diffraction, SEM-EDS, and Raman spectroscopy. Jamborite crystallizes in the space group REmbedded Imagem, with the unit-cell parameters a 3.068(4) Å, c 23.298(11) Å, and Z = 3. The structure refinement (R1 = 0.0818) showed that jamborite contains brucite-like sheets of edge-sharing octahedra (Ni2+,M3+)(O,OH)6 with a distinctive double layer of partially occupied H2O molecules between them. Raman data indicate that the sulfur is present as sulfate rather than sulfide. The new analytical data were recalculated on the basis of 1 (Ni+Ca+Co+Fe) to give the formula [(Ni2+0.902Ca2+0.002)(Co3+0.072Fe3+0.024)]Σ1.000(OH)1.884Cl0.012(H2O)0.004(SO4)0.100·0.900H2O. The sulfur occupancy was too low to be located in the refinement, but the ≈1:1 ratio of M3+:S from the chemical analysis implies that SO42− replaces OH− in the brucite sheet rather than sitting in the interlayer space. The splitting of the H2O layer allows avoidance of short SO42−···H2O distances. Thus, jamborite is not a member of the hydrotalcite supergroup. Jamborite is redefined as M2+1−xM3+x(OH)2−x(SO4)x·nH2O, where M2+ is dominantly Ni, M3+ is dominantly Co, x ≤ 1/3 and probably ≤ 1/7 (x = 0.10 for the neotype sample), and n < (1−x). The low M3+/M2+ ratio relative to honessite and hydrohonessite and high Co content may explain the rarity of jamborite as an early alteration product of millerite. The redefinition of jamborite and designation of the neotype specimen from Rio Vesale have been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC), voting proposal 14-E

Hydroxyferroroméite, a new secondary weathering mineral from Oms, France

Hydroxyferroroméite, ideally (Fe2+ 1.5[]0.5)Sb5+ 2O6(OH), is a new secondary mineral from the Correc d'en Llinassos, Oms, Pyrénées-Orientales Department, France. Hydroxyferroroméite occurs as yellow to yellow-brown powdery boxwork replacements up to about 50μm across after tetrahedrite in a siderite–quartz matrix. No distinct crystals have been observed. The empirical formula (based on 7 (O + OH) per formula unit, pfu) is (Fe2+ 1.07Cu2+ 0.50Zn0.03Sr0.03Ca 0.01[]0.36)Σ2 (Sb5+ 1.88Si0.09Al0.02As0.01)Σ2 O6 ((OH)0.86 O0.14). X-ray photoelectron spectroscopy was used to determine the valence states of Sb, Fe and Cu. Hydroxyferroroméite crystallises in the space group Fd3 m with the pyrochlore structure and hence is a new Fe2+ -dominant member of the roméite group of the pyrochlore supergroup. It has the unit-cell parameters: a = 10.25(3) Å, V = 1077(6) Å3 and Z = 8. A model, based on bond-valence theory, for incorporation of the small Fe2+ cation into a displaced variant of the A site of the pyrochlore structure is proposed.The attached document is the author(’s’) final accepted/submitted version of the journal article. You are advised to consult the publisher’s version if you wish to cite from it

Micro-Raman study of crichtonite group minerals enclosed into mantle garnet

We report the first comprehensive micro-Raman study of crichtonite group minerals (CGM) as inclusions in pyropic garnet grains from peridotite and pyroxenite mantle xenoliths of the Yakutian kimberlites as well as in garnet xenocrysts from the Aldan shield lamprophyres (Russia). The CGM form (i) morphologically oriented needles, lamellae, and short prisms and (ii) optically unoriented subhedral to euhedral grains, either single or intergrown with other minerals. We considered common mantle-derived CGM species (like loveringite, lindsleyite, and their analogues), with Ca, Ba, or Sr dominating in the dodecahedral A site and Zr or Fe in the octahedral B site. The Raman bands at the region of 600–830 cm−1 are indicative of CGM and their crystal-chemical distinction, although the intensity and shape of the bands appear to be dependent on laser beam power and wavelength. The factor-group analysis based on the loveringite crystal structure showed the octahedral and tetrahedral cation groups with 18f and 6c Wyckoff positions, namely, dominantly TiO6 and to a lower extent CrO6, MgO4, and FeO4 groups, to be the major contributors to the Raman spectral features. The ionic groups with dodecahedral (M0) and octahedral (M1) coordination are inactive for Raman scattering while active in infrared absorption. A number of observed Raman modes in the CGM spectra are several times lower than that predicted by the factor group analysis. The noticed broadening of modes in the CGM Raman spectra may result from a combining of bands at the narrow frequency shift regions. Solid solution behavior, luminescence, and partial metamictization of the CGM may exert additional influence on the Raman band shape. The Raman spectral features showed CGM to be accurately identified and distinguished from other Ti-, Fe-, Cr-, and Zr-containing oxides (e.g., ilmenite or those of spinel and magnetoplumbite groups) occurring as accessory mantle minerals. © 2020 The Authors. Journal of Raman Spectroscopy published by John Wiley & Sons LtdRussian Science Foundation, RSF: 18‐77‐10062Council on grants of the President of the Russian FederationThis study was supported by the Russian Science Foundation (Grant 18‐77‐10062). The equipment of the Ural Center for Shared Use «Modern Nanotechnology», Ural Federal University, and the Analytical Center for Multi‐elemental and Isotope Research, IGM, was used. Sampling was supported by the Russian Federation state assignment project of IGM. We are grateful to Nikolai V. Sobolev for Samples O‐173, O‐39, and O‐264. Vladimir N. Korolyuk, Elena N. Nigmatulina (IGM), and Allan Patchen (UT) are highly appreciated for the help with EMP analyses. We express our sincere thanks to F. Nestola and an anonymous reviewer for their thorough reviews and helpful suggestions, and to C. Marshall for regardful editorial handling of the manuscript on every stage of its revision

Ottensite, brizziite and mopungite from Pereta mine (Tuscany, Italy) : new occurrences and crystal structure refinement of mopungite

Ottensite, Na3 (Sb2O3)(SbS3)\ub73H2O, brizziite, NaSbO3, and mopungite, NaSb(OH)6, have been found on several specimens from the antimony mine of Pereta (Grosseto, Tuscany, Italy). Ottensite from Pereta mine occurs as brilliant reddish-brown spheroidal aggregates, with a diameter up to 0.2 mm, formed by radially oriented individuals. These aggregates are associated with well-shaped tabular and pseudocubic colourless crystals of mopungite and platy aggregates of brizziite. This is the second world occurrence of ottensite and brizziite. The mineral species were characterized by electron microprobe analysis, X-ray diffraction study and microRaman spectroscopy. Single-crystal X-ray diffraction data were collected on a twinned crystal of mopungite and the structure was for the first time refined on a natural sample in space group P42/n [unit cell parameters a = 8.036(3) \uc5, c = 7.926(6) \uc5, V = 511.88(5) \uc53, Z = 4] obtaining an R1-index of 5.17, wR2 of 13.52 and GooF of 1.247

Fluorcarmoite-(Bana), the first mg-dominant mineral of the arrojadite group

Fluorcarmoite-(BaNa), ideallyA1BaA2\u2073B1,2NaNa1,2NaNa32 \u2073CaCaMMg13Al(PO4)11(PO3OH)WF2, was found in a pebble of the riverbed of the upper Maremola Creek, close to the village of Isallo, in the Magliolo municipality (Savona, Liguria, Italy). The root-name is after Monte Carmo di Loano, the highest peak in the area, namesake of the tectonic unit where the mineral was found and the first locality where phosphate mineralization has been found in the region. The mineral is associated with quartz and almandine and has microscopic inclusions of fluorapatite and possible graftonite. It occurs as yellow\u2013orange and translucent crystals in an anhedral centimetric nodule embedded in quartz. Fluorcarmoite-(BaNa) is brittle, and no cleavage or parting was observed. It has a yellow\u2013orange streak, a vitreous lustre, does not fluoresce under shortwave or longwave ultraviolet light and is weakly pleochroic (light yellow). Fluorcarmoite-(BaNa) is optically biaxial positive, with \u3b1 = 1.6240(5), \u3b2 = 1.6255(5), \u3b3 = 1.6384(5) (589 nm), 2Vmeas = 35(2)\ub0 and 2Vcalc = 37.9\ub0. Raman spectroscopy shows the presence of weak bands in the OH-stretching region. The average chemical composition is (wt%, wavelength-dispersive-mode electron microprobe): Na2O 5.83, K2O 0.36, CaO 2.64, SrO 0.46, BaO 7.12, MnO 2.01, FeO 17.68, MgO 15.12, Al2O3 2.57, P2O5 44.96, F 2.14, \u2013O =F2 0.90, H2Ocalc 0.33, total 100.32. The empirical formula calculated on the basis of 50 O + F + (OH) atoms per formula unit (apfu), is: (Na3.77Ca0.94Ba0.93 K0.15Sr0.090.12)\u3a3=6.00(Mg7.52Fe2+ 4:93Mn2+0:57)\u3a3=13.02Al1.01(PO4)11(PO3)(OH0.74F0.26)F2. Strongest lines in the X-ray powder diffraction pattern are [d in \uc5 (Icalc) hkl]: 4.959 (25) 020, 4.524 (20) 114, 3.188 (28) 206, 3.012 (100) 424, 2.735 (32) 602, 2.682 (39) 226, 2.526 (25) 424. The crystal structure has been refined using single-crystal X-ray diffractometer data (Rint = 4.1%) in space group Cc (no. 14) to R1 = 0.0342 for 11 511 reflections with Fo >4\u3c3|F| and 0.0417 for all 13 232 data. Refined unit-cell parameters are: a = 16.4013(3) \uc5, b = 9.9487(1) \uc5, c = 24.4536(8) \uc5, \u3b2 = 105.725(2)\ub0, V = 3840.80(15) \uc53 (Z = 4). Fluorcarmoite-(BaNa) is the first Mg-dominant mineral of the arrojadite group. Mg orders preferentially in the M1, M2b, M3a,b, M4a,b and M7a,b sites whereas the non-dominant Fe2+ and very minor Mn2+ show site preference for M2a, M5a,b and M6a,b. The A1 site is mostly populated by Ba, the A2 site is empty, and minor Fe2+ occurs at the B1b site. A significant, but not dominant occupancy of the Na3 site by Na is also observed. Only Ca and Al are present at the Ca and Al sites, respectively. The type material is deposited in the mineralogical collection of the Museo Regionale di Scienze Naturali di Torino, Sezione di Mineralogia, Petrografia e Geologia, Torino (Italy). The mineral and its name have been approved by the IMA-CNMNC (2015-062)

As-bearing new mineral species from Valletta mine, Maira Valley, Piedmont, Italy : II. Braccoite, NaMn2+5[Si5AsO17(OH)](OH), description and crystal structure

The new mineral species braccoite, ideally NaMn2+5[Si5AsO17(OH)](OH), has been discovered in the Valletta mine dumps, in Maira Valley, Cuneo province, Piedmont, Italy. Its origin is probably related to the reaction between ore minerals and hydrothermal fluids. It occurs as subhedral crystals in brown-red coloured thin masses, with a pale-yellow streak and vitreous to resinous lustre. Braccoite is associated with tiragalloite, for which new data are provided, as well as gamagarite, hematite, manganberzeliite, palenzonaite, quartz, saneroite, tokyoite, unidentified Mn oxides, organic compounds, and Mn arsenates and silicates under study. Braccoite is biaxial positive with refractive indices \u3b1 = 1.749(1), \u3b2 = 1.750(1), \u3b3 = 1.760(1). It is triclinic, space group P1, with a = 9.7354(4), b = 9.9572(3), c = 9.0657(3) \uc5, \u3b1 = 92.691(2), \u3b2 = 117.057(4), \u3b3 = 105.323(3)\ub0, V = 740.37(4) \uc53 and Z = 2. Its calculated density is 3.56 g/cm3. The ten strongest diffraction lines of the observed powder X-ray diffraction (XRD) pattern are [d in \uc5, (I), (hkl)]: 3.055 (69)(221), 3.042 (43)(102), 3.012 (65)(321), 2.985 (55)(231), 2.825 (100)(213), 2.708 (92)(220), 2.627 (43)(232), 2.381 (58)(411), 2.226 (25)(214) and 1.680 (433)(36). Chemical analyses by wavelength-dispersive spectroscopy electron microprobe gave (wt.%): Na2O 4.06, CaO 0.05, MnO 41.76, MgO 0.96, Al2O3 0.04, CuO 0.02, SiO239.73, As2O5 6.87, V2O5 1.43, SO3 0.01 and F 0.04. H2O 2.20 was calculated on the basis of 2OH groups p.f.u. Raman spectroscopy confirmed the presence of (SiO4)4-, (AsO4)3- and OH groups. The empirical formula, calculated on the basis of \u3a3 cations-(Na,K) = 11 p.f.u., in agreement with the results of the crystal structure, is Na1.06(Mn2+4.46Mn3+0.32Mg0.19V3+0.01Al0.01Ca0.01)[Si5(As0.48Si0.37V5+0.15)O17(OH)](OH0.98F0.02); the simplified formula is Na(Mn,Mg,Al,Ca)5[Si5(As,V,Si)O17(OH)](OH,F). Single-crystal XRD allowed the structure to be solved by direct methods and revealed that braccoite is the As-dominant analogue of saneroite. The structure model was refined on the basis of 4389 observed reflections to R 1 = 3.47%. Braccoite is named in honour of Dr Roberto Bracco (b. 1959), a systematic minerals collector with a special interest in manganese minerals. The new mineral was approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA 2013-093)