X-ray Powder Diffraction Lines Research Articles

Bobfinchite, Na[(UO2)8O3(OH)11]·10H2O, a new Na-bearing member of the schoepite family

Abstract The new mineral bobfinchite (IMA2020-082), Na[(UO2)8O3(OH)11]·10H2O, was found in the Burro mine, Slick Rock district, San Miguel County, Colorado, U.S.A., where it occurs as an oxidation product of uraninite on asphaltite matrix in intimate association with gypsum, natrozippeite, metaschoepite, and uranopilite. Bobfinchite crystals are transparent to translucent, yellow, lozenge-shaped disks up to 0.3 mm wide. Crystals are flattened on [100] and exhibit the forms {100}, {011}, {021}, {021}, and {011}. Bobfinchite has a pale-yellow streak and emits very dim yellow fluorescence under 365 nm ultraviolet illumination. The crystals are brittle with very good {100} cleavage and irregular, stepped fracture. The Mohs hardness is ca. 2 based on scratch tests. The calculated density is 5.044 g/cm3 based on the empirical formula and 5.036 g/cm3 for the ideal formula. Bobfinchite is optically biaxial (–), with α = 1.690(5), β = 1.7205(5), and γ = 1.730(5) (white light). The measured 2V, estimated from the interference figure, is 55(5)° and the calculated value is 59.1°. Dispersion is moderate, r > v; orientation: X = a, Y = b, Z = c; pleochroism: X nearly colorless, Y yellow, Z yellow; X < Y ≈Z. Electron microprobe analysis provided the empirical formula (Na0.99Pb0.02)[(UO2)7.99O3(OH)11]·10H2O. The five strongest X-ray powder diffraction lines are [dobs in Å(I)(hkl)]: 7.34(100)(200), 3.59(50)(024), 3.23(60)(224), 3.18(36)(240), and 2.01(23)(624,551,208,640,346). Bobfinchite is orthorhombic, Pbcn, a = 14.6249(9), b = 14.0389(10), c = 16.6923(10) Å, V = 3427.2(4) Å3, and Z = 4. The structure of bobfinchite (R1 = 0.0330 for 3770 I > 4σI) is built from uranyl oxide-hydroxide sheets that adopt the fourmarierite topology, with interlayer Na+ and H2O groups. Both the sheet and interlayer topology mimic those observed in natural and synthetic Na-metaschoepites studied previously, and as seen in other uranyl oxide hydrate minerals, charge balance is achieved at specific sites in the sheet through the substitution O2– ↔ (OH)–.

Theuerdankite, Ag3AsO4, a new mineral from the Alter Theuerdank Mine, St. Andreasberg, Germany

Abstract The new mineral theuerdankite, ideally Ag3AsO4, was found in the Alter Theuerdank Mine, Beerberg, St. Andreasberg, Goslar District, Lower Saxony, Germany. Theuerdankite occurs as aggregates of anhedral grains up to 3 mm in size, growing in cavities of strongly supergene-weathered material consisting of native silver and chlorargyrite (but with calcite present). It is dark violet, changing to reddish and black when exposed to the air and light. It has a grey to violet grey streak; when readily fresh, its streak is brownish-red. The Mohs hardness is ~2. It is brittle with no observable cleavage or parting and with a conchoidal fracture. The calculated density is 6.620 g⋅cm–3. In reflected light, theuerdankite is dark grey with a pinkish tint, with no observable bireflectance, pleochroism, or anisotropy. It shows dark red internal reflections. The reflectance values for wavelengths recommended by the Commission on Ore Mineralogy of the International Mineralogical Association are (R, %): 13.3 (470 nm), 12.8 (546 nm), 12.7 (589 nm) and 12.5 (650 nm). The empirical formula (based on 4 apfu) is Ag3.00As1.00O4. Theuerdankite is cubic, space group P $\bar{4}$ 3n, a = 6.144(2) Å, V = 231.93(13) Å3 and Z = 2. The six strongest powder X-ray diffraction lines are [dobs in Å, (I) hkl]: 3.0736, (22) 200; 2.7502, (100) 210; 2.5106, (55) 211; 1.7050, (36) 320; 1.6249, (44) 321; and 1.3412, (17) 421. The crystal structure of theuerdankite (R1 = 1.69% for 519 reflections having I > 3σ(I)), is isotypic to those of synthetic Ag3AsO4 and Ag3PO4. The Gram–Charlier development describing the higher-order tensors representing the atomic displacement parameters of the silver atom was implemented, documenting that silver tends to behave anharmonically in the theuerdankite structure at room temperature.

Kenoargentotetrahedrite-(Zn), [Ag6]4+(Cu4Zn2)Sb4S12□, a new member of the tetrahedrite group from the Yindongpo Au deposit, China

Abstract. The new mineral kenoargentotetrahedrite-(Zn), [Ag6]4+(Cu4Zn2)Sb4S12□, was discovered at the Yindongpo Au deposit, Henan Province, China. It occurs as black metallic anhedral grains or equant crystals up to 40 µm in size. It is opaque in transmitted light and shows a greenish-grey colour in reflected light. Electron microprobe analysis for the studied material gave the empirical formula (on the basis of total cations being equal to 16 atoms per formula unit, apfu): M(2)(Ag3.75Cu2.25)Σ6M(1)[Cu3.90(Zn1.18Fe0.69Cd0.26)Σ2.13]Σ6.03X(3)(Sb3.69As0.27)Σ3.96S(1)S11.94 S(2)□. Kenoargentotetrahedrite-(Zn) is cubic, I4‾3m (no. 217), with a = 10.4624(4) Å, V= 1145.23(13) Å3, and Z= 2. The crystal structure has been refined to a final value of R1= 0.0247 on the basis of 274 independent reflections (Fo > 4σ (Fo)) by using single-crystal X-ray diffraction data. The seven strongest X-ray powder diffraction lines (d in Å (I) (hkl)) are the following: 3.010 (100) (222), 1.844 (30) (044), 2.606 (22) (004), 1.572 (15) (226), 2.046 (9) (134), 7.35 (6) (011), and 1.909 (5) (125). Kenoargentotetrahedrite-(Zn) is isostructural with other keno-member tetrahedrites with the [Ag6]4+ cluster. The structure refinement result confirms the coupling between the site occupancy factor of subvalent hexasilver clusters at the M(2) site and that of the vacancy at the S(2) site. This relationship further substantiates the charge balance substitution mechanism of S-deficiency tetrahedrites: 6M(2)Ag++S(2)S2-= M(2)[Ag6]4++S(2)□.

A re-evaluation of stannopalladinite using modern analytical techniques

AbstractAn investigation of sample 41647 from the Platinum Placer of Ugol'nyi Ruchei, Norilsk Cu–Ni deposit, Russia, stored in the systematic collection of the Fersman Mineralogical Museum, revealed that it contained a mineral that can be identified as the original stannopalladinite described in 1947. As the literature information on the latter is controversial, the mineral was re-investigated using modern analytical techniques. Stannopalladinite occurs as spherical and ovoid-shaped grains up to 0.08 mm, closely intergrown with tetraferroplatinum as part of flattened, prismatic crystals up to 6 mm long. The micro-indentation hardness of stannopalladinite (VHN, 30 g load) is 244 kg/mm2 (range 233–266, n = 4), corresponding to a Mohs hardness of 4. The calculated density is 9.781 g/cm3. In reflected light, stannopalladinite is pale pink. The bireflectance is noticeable only in oil immersion. In crossed nicols the mineral exhibits strong anisotropy with colour effects changing from reddish purple to greyish blue and polysynthetic twinning of grains. The reflectance curves show distinct anomalous dispersion. The chemical composition (wt.%, electron microprobe data, mean of 11 analyses) is: Cu 8.48, Pd 61.21, Pt 0.89, Sn 25.87, Pb 3.70, total 100.15. The empirical formula calculated on the basis of 4 atoms per formula unit is (Pd2.42Cu0.56Pt0.02)Σ3.00(Sn0.92Pb0.08)Σ1.00. The ideal chemical formula of stannopalladinite is therefore proposed as (Pd,Cu)3Sn instead of Pd3Sn2 used in the official IMA List of Minerals. The strongest powder X-ray diffraction lines are [dobs, Å (I, %) (hkl) ]: 2.292 (42) (231), 2.166 (100) (331), 2.034 (10) (710), 1.916 (15) (141) and 1.851 (15) (630). The powder X-ray data are indexed in the orthorhombic unit cell with a = 14.634(2), b = 8.5253(6), c = 4.5946(3) Å and V = 573.24(7) Å3 (Z = 8). Stannopalladinite can be reliably identified among all other minerals belonging to the binary Pd–Sn and ternary Pd–Cu–Sn systems by a combination of chemical, optical and X-ray data.

Stibiotantalite from the Nanyangshan LCT Pegmatite, North Qinling Orogen, Central China: Occurrence and New Data on its Crystal Chemistry

ABSTRACT Stibiotantalite, SbTaO4, from the Nanyangshan LCT pegmatite, North Qinling Orogen, Central China is described. The mineral is associated with oxystibiomicrolite, oxycalcioroméite, hydrokenomicrolite, hydroxynatromicrolite, hydromicrolite, stibnite, bismuthinite, tantalite-(Mn), columbite-(Mn), spodumene, polylithionite, trilithionite, luanshiweiite, fluorluanshiweiite, elbaite, albite, and quartz. Results from electron microprobe data analysis (n = 4) yield the average empirical formula (based on O = 4): (Sb0.96Bi0.04)Σ1.00(Ta0.85Nb0.15)Σ1.00O4. The seven strongest X-ray powder diffraction lines are [d in Å (I)(hkl)] 3.126(100)(121), 2.964(81)(040), 5.976(27)(020), 3.515(22)(111), 1.891(22)(240), 1.736(19)(161), and 2.693(16)(131). Single-crystal X-ray diffraction (SXRD) patterns show strong reflections consistent with space group Pna21. The refined unit-cell parameters from the SXRD data are a 5.5419(2) Å, b 4.9200(2) Å, c 11.8003(5) Å, and V 321.75(2) Å3 with Z = 4. The structure has been refined to a final R1 = 0.0173 on the basis of 766 reflections with Fo > 4σ(Fo). In the previous study, the AO6 octahedron of stibiotantalite was close to an ideal octahedron. The new structure refinement of stibiotantalite from the Nanyangshan pegmatite indicates that the AO6 octahedron has a larger distortion due to the lone-pair effect of Sb3+. The high-quality structural data presented in this study gives a more accurate portrayal of the crystal structure of stibiotantalite than provided in the original description of the mineral.

Aluminotaipingite-(CeCa), (Ce6Ca3)Al(SiO4)3[SiO3(OH)]4F3, a new member of the cerite-supergroup minerals

AbstractAluminotaipingite-(CeCa), (Ce6Ca3)Al(SiO4)3[SiO3(OH)]4F3, is a new member of the cerite-supergroup minerals, whose general chemical formula is A9XM[TO3Ø]7Z3, (A = REE, Ca, Sr, Na and □; X = □, Ca, Na and Fe2+; M = Mg, Fe2+, Fe3+, Al and Mn; T = Si and P; Ø = O and OH; Z = □, OH and F). It was found in cavities of a leucogranitic orthogneiss at the Casette quarry, Montoso, Bagnolo Piemonte, Cuneo Province, Piedmont, Italy. Crystals of aluminotaipingite-(CeCa) are light pink to pink, transparent or semi-transparent, with a vitreous lustre. It forms pyramidal crystals up to 0.07 mm in size and observed forms are {0 0 1}, {1 0 $\bar{2}$}. The tenacity is brittle, no distinct cleavage is observed and the fracture is uneven. The mineral does not fluoresce in long- or short-wave ultraviolet light. The streak is white. Hardness (Mohs) = 5. The calculated density is 4.476 g cm–3.The mineral is trigonal, space group R3c, with a = 10.658(3), c = 37.865(9) Å, V = 3725(2) Å3 and Z = 6. The eight strongest powder X-ray diffraction lines are [dobs, Å (I, %) (h k l)]: 8.38(29)(0 1 2), 4.499(28)(2 0 2), 3.282(41)(2 1 4), 2.936(100)(0 2 10), 2.816(51)(1 2 8), 2.669(37)(2 2 0), 2.207 (29)(3 0 12) and 1.935(35)(2 3 8). The structure was refined to R =0.0306 for 2297 reflections with I >2σ(I). The crystal structure of aluminotaipingite-(CeCa) contains two nine-fold coordinated sites (A1 and A2), which are occupied mainly by lanthanides, and a third nine-fold coordinated A3 site containing almost equal amounts of lanthanides and Ca. The X site is vacant and at the octahedral M site aluminium prevails over Fe3+. Among the three independent T sites, T2 belongs to a (SiO4)4– anion, whereas T1 and T3 belong to (SiO3OH)3– anions. Fluorine is involved in coordination with the A1 and A3 sites.

Tennantite-(Ni), Cu6(Cu4Ni2)As4S13, from Luobusa ophiolite, Tibet, China: a new Ni member of the tetrahedrite group

AbstractThe new mineral tennantite-(Ni), Cu6(Cu4Ni2)As4S13, has been discovered from the Luobusa Chromitite, Tibet, southwestern China. Tennantite-(Ni) occurs as anhedral grains ranging from 2 to 20 μm in size. In reflected light microscopy, tennantite-(Ni) is isotropic and appears yellow-greenish grey. Reflectance data for Commission on Ore Mineralogy wavelengths in air for tennantite-(Ni) are: 31.0 (470 nm), 29.6 (546 nm), 29.6 (589 nm) and 29.3 (650 nm). Electron microprobe analysis for holotype material gave the empirical formula (on basis of total cations = 16 apfu): M(2)Cu6M(1)[Cu4.00(Ni0.97Cu0.53Fe0.50)Σ2.00]Σ6.00X(3)(As2.94Sb1.06)Σ4S12.77. Tennantite-(Ni) is cubic, with space group I$\bar{ 4}$3m (#217), a =10.2957(9) Å, V = 1091.4(3) Å3 and Z = 2. By using single-crystal X-ray diffraction, the crystal structure has been determined and refined to a final R1 = 0.0423 on the basis of 163 independent reflections [Fo > 4σ (Fo)]. The calculated seven strongest powder X-ray diffraction lines [d in Å (I) (hkl)] are: 2.972 (100) (222), 1.820 (83) (440), 2.574 (28) (400), 1.552 (18) (622), 3.640 (10) (220), 1.880 (10) (521) and 1.287 (7) (800). Tennantite-(Ni) is isostructural with other tetrahedrite-group minerals, and nickel is hosted at the tetrahedrally coordinated M(1) site, along with Cu and minor Fe. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2021-018).

Ruizhongite, (Ag2☐)Pb3Ge2S8, a thiogermanate mineral from the Wusihe Pb-Zn deposit, Sichuan Province, Southwest China

Abstract Ruizhongite (IMA2022-066), (Ag2☐)Pb3Ge2S8, is a thiogermanate of economic importance discovered in the Wusihe Pb-Zn deposit in Sichuan Province, southwestern China. This mineral occurs as anhedral grains 1–10 μm in size. It is gray and opaque, with a metallic luster and black streak, closely associated with galena and pyrite in a sphalerite matrix. Under reflected light, it displays a greenish-gray color without internal reflection. Its reflectance values in air (R %) based on SiC as the reference material are 30.5, 32.2, 34, and 34.1 for corresponding wavelengths of 650, 589, 470, and 546 nm, respectively. According to the average of 18 electron microprobe analyses, Pb (57.37 wt%), S (21.39 wt%), Ge (11.53 wt%), Ag (7.34 wt%), Zn (1.57 wt%), and Fe (0.27 wt%) constitute 99.46 wt% of ruizhongite. The empirical formula based on the 8 S apfu is (Ag0.82Pb0.32Zn0.28Fe0.06)Σ1.48Pb3Ge1.9S8, and (Ag2☐)Pb3Ge2S8 is its ideal formula. Ruizhongite displays a cubic structure, space group I43d (#220), with the unit-cell parameters a = 14.0559(2), V = 2777.00(7), Z = 8, and the calculated density is 5.706 g/cm3. The strongest powder X-ray diffraction lines [d in Å (I) (hkl)] are 3.755 (100) (123), 3.511 (76) (004), 2.992 (73) (233), 2.574 (21) (125), 2.482 (79) (044), 2.276 (46) (235), 1.784 (39) (237), and 2.075 (24) (136). The structure of ruizhongite was determined using single-crystal XRD and was refined to an R1 of 0.0323 for all 2594 (474 unique) reflections. The structure comprises a non-centrosymmetric arrangement of [GeS4]4− tetrahedra, forming two interstice sites: fully occupied Pb1 and partially occupied Ag1, aligned in the directions of a-, b-, and c-axes. Ruizhongite was named in honor of Ruizhong Hu (1958), an eminent Chinese ore geochemist. The discovery of ruizhongite has significant implications for the occurrence and enrichment mechanism of Ge in sphalerite and other metallic minerals.

Calcioancylite-(La), (La,Ca)2(CO3)2(OH,H2O)2, a new member of the ancylite group from Gejiu nepheline syenite, Yunnan Province, China

AbstractCalcioancylite-(La), ideally (La,Ca)2(CO3)2(OH,H2O)2, has been discovered from nepheline syenite of the Gejiu alkaline complex in the Honghe Hani and Yi Autonomous Prefecture, Yunnan Province, China. The mineral occurs as aggregates of subhedral grains, and the size of single crystals varies between 5–20 μm. Calcioancylite-(La) is colourless to pale pinkish grey and has transparent to translucent lustre. It is brittle with a Mohs hardness of 4. The calculated density is 4.324 g/cm3. The mineral is biaxial (−), with α =1.662, β = 1.730, γ = 1.771, 2Vmeas. = 70°(1) and 2Vcalc. = 73°. Electron microprobe analysis for holotype material yielded an empirical formula of (La0.58Ce0.55Pr0.14Nd0.10Ca0.39Sr0.20K0.04)Σ2.00(CO3)2[(OH)1.25F0.06⋅0.69H2O]Σ2.00. Calcioancylite-(La) is orthorhombic, with space group Pmcn, a = 5.0253(3) Å, b = 8.5152(6) Å, c = 7.2717(6) Å, V = 311.17(4) Å3 and Z = 2. By using single-crystal X-ray diffraction, the crystal structure has been determined and refined to a final R1 = 0.0652 on the basis of 347 independent reflections (I > 2σ). The seven strongest powder X-ray diffraction lines [d in Å (I) (hkl)] are: 2.334 (100) (013), 2.970 (80) (121), 4.334 (75) (110), 3.678 (68) (111), 2.517 (55) (200), 2.647 (47) (031) and 2.077 (44) (221). Calcioancylite-(La) is the La-analogue of calcioancylite-(Ce) and is a new member of ancylite-group minerals. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2021-090).

Argentopolybasite, Ag16Sb2S11, a new member of the polybasite group

AbstractThe new mineral argentopolybasite, ideally Ag16Sb2S11, was found at the Kremnica Au–Ag epithermal deposit, Žiar nad Hronom Co., Banská Bystrica Region, Slovakia (type locality), Šibeničný vrch near Nová Baňa, Žarnovica Co., Banská Bystrica Region, Slovakia (cotype locality) and the Arykevaam epithermal Au–Ag deposit, Anadyr’ District, Chukotka Autonomous Okrug, Russian Federation (cotype locality). At the Kremnica deposit argentopolybasite was found as discrete, well-developed (pseudo)hexagonal tabular crystals up to 4 mm in size or as complex crystalline aggregates and groups up to 5 mm in size in cavities of quartz. It is associated with pyrargyrite, polybasite, stephanite, miargyrite, rozhdestvenskayaite-(Zn), argentotetrahedrite-(Zn), naumannite, gold and pyrite. Argentopolybasite is dark grey to black, with a black streak and metallic to opaque lustre. The Mohs hardness is ~3. It is brittle with no observable cleavage and with a conchoidal fracture. The calculated density is 6.403 g⋅cm–3. In reflected light, argentopolybasite is grey, with no observable bireflectance and very weak pleochroism. It shows moderate anisotropy in crossed polarisers with weak greenish and green–blue tints. The reflectance values for wavelengths recommended by the Commission on Ore Mineralogy of the IMA are (Rmin/Rmax, %): 30.3/31.0 (470 nm), 28.8/29.3 (546 nm), 28.1/28.6 (589 nm) and 27.4/27.8 (650 nm). The empirical formulae (based on 29 apfu) are, Kremnica: (Ag15.94Cu0.18)Σ16.12(Sb1.40As0.61)Σ2.01(S10.60Se0.25Cl0.03)Σ10.88, Nová Baňa: Ag16.30(Sb1.74As0.22)Σ1.96(S10.69Cl0.04)Σ10.73 and Arykevaam: (Ag15.54Cu0.38)Σ15.92(Sb1.56As0.51)Σ2.07S11.01. The ideal end-member formula for argentopolybasite is Ag16Sb2S11. Argentopolybasite is trigonal, space group P321, a = 15.0646(5) Å, c = 12.2552(5) Å, V = 2408.61(15) Å3 and Z = 2. The seven strongest powder X-ray diffraction lines are [dobs in Å, (I), hkl]: 12.169, (40), 001; 3.162, (100), 041; 3.045, (54), 004; 2.881, (45), 042; and 2.4256, (28), 421. The crystal structure of argentopolybasite from Kremnica, refined to Robs = 0.0741 for 2804 observed reflections, confirmed that the atomic arrangement is isotypic to that of the other members of the polybasite group and it is isostructural with argentopearceite.

Comment on "Structural transition and superconductivity in hydrothermally synthesized FeX (X = S, Se)" by U. Pachmayr, N. Fehn and D. Johrendt, Chem. Commun., 2016, 52, 194.

The occurrence of triclinic structural modification of β-FeSe was reported in the literature; in particular this polymorph was claimed to be observed at low temperature in samples prepared by hydrothermal synthesis. The establishment of triclinic symmetry was argued based on peculiar features characterizing some selected X-ray powder diffraction lines. Using high-resolution synchrotron X-ray powder diffraction, the same features were observed for an aged β-FeSe sample prepared by a solid state synthesis technique. Moreover, by refining the anisotropic microstrain parameters it was demonstrated that the diffraction pattern can be fairly fitted by applying the well-recognized orthorhombic structural model adopted for the low temperature phase of β-FeSe. This result indicates that the occurrence of the triclinic polymorph for β-FeSe can be ruled out.

Shinarumpite, a new cobalt uranyl sulfate mineral from the Scenic mine, San Juan County, Utah, USA, structurally related to leydetite

AbstractThe new mineral shinarumpite (IMA2021-105), [Co(H2O)6][(UO2)(SO4)2(H2O)]⋅4H2O, was found in the Scenic mine on Fry Mesa, White Canyon district, San Juan County, Utah, USA, where it occurs as a secondary phase on granular quartz matrix in association with gypsum, deliensite, Co-rich rietveldite, scenicite, shumwayite and sulfur. Shinarumpite crystals are transparent, yellow, blades or prisms, up to 1 mm in length. The mineral has white streak, vitreous lustre and is nonfluorescent. It is brittle with irregular, curved fracture. The Mohs hardness is ~2½ and it has a perfect {100} cleavage. The density is 2.58(2) g⋅cm–3. Optically, the mineral is biaxial (–) with α = 1.515(2), β = 1.526(2), γ = 1.529(2) (white light); 2V = 55(1)°; extreme r < v dispersion; orientation: Z = b, X ^ a = 30° in obtuse β; pleochroism: X = very pale yellow, Y = pale yellow, Z = light yellow; X < Y < Z. The Raman spectrum exhibits bands consistent with UO22+, SO42– and O–H. Electron microprobe analysis provided the empirical formula [(Co0.51Ni0.28Fe0.21)Σ1.00(H2O)6][(UO2)(SO4)2(H2O)]⋅4H2O. The five strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 10.37(100)(200), 5.73(43)(111), 5.20(70)(400, 202, 211), 4.70(31)($\bar{3}$11) and 3.326(30)(213, 021). Shinarumpite is monoclinic, P21/c, a = 21.0549(15), b = 6.8708(5), c = 12.9106(5), β = 96.678(7)°, V = 1885.03(17) Å3 and Z = 4. In the structure of shinarumpite (R1 = 0.0336 for 2623 I > 2σI), linkages of pentagonal bipyramids and tetrahedra form an infinite [(UO2)(SO4)2(H2O)]2– sheet. Isolated Co(H2O)6 octahedra and H2O groups occupy the interlayer region linking the sheets via an extensive system of hydrogen bonds. The structure of shinarumpite is very similar to that of leydetite. Uranyl sulfate structural unit types are discussed with respect to frequency and charge deficiency per anion (CDA).

Piccoliite, NaCaMn3+2(AsO4)2O(OH), a new arsenate from the manganese deposits of Montaldo di Mondovì and Valletta, Piedmont, Italy

AbstractPiccoliite, ideally NaCaMn3+2(AsO4)2O(OH), is a new mineral discovered in the Fe–Mn ore hosted in metaquartzites of the Montaldo di Mondovì mine, Corsaglia Valley, Cuneo Province, Piedmont, Italy. It occurs as small and rare black crystals and aggregates hosted by a matrix of quartz, associated with calcite and berzeliite/manganberzeliite. It has been also found in the Valletta mine near Canosio, Maira Valley, Cuneo Province, Piedmont, Italy, where it occurs embedded in quartz associated with grandaite, hematite, tilasite/adelite and rarely thorianite. The mineral is opaque (thin splinters may be very dark red), with brown streak and has a resinous to vitreous lustre. It is brittle with irregular fracture. No cleavage has been observed. The measured Mohs hardness is ~5–5.5. Piccoliite is non fluorescent. The calculated density is 4.08 g⋅cm–3. Chemical spot analyses by electron microprobe analysis using wavelength dispersive spectroscopy resulted in the empirical formula (based on 10 anions per formula unit) (Na0.64Ca0.35)Σ0.99(Ca0.75Na0.24)Σ0.99(Mn3+1.08Fe3+0.59Mg0.20Ca0.10)Σ1.97(As2.03V0.03Si0.01)Σ2.07O9(OH) and (Na0.53Ca0.47)Σ1.00(Ca0.76Na0.23Sr0.01)Σ1.00(Mn3+0.63Fe3+0.49Mg0.48Mn4+0.34Ca0.06)Σ2.00(As1.97P0.01Si0.01)Σ1.99O9(OH) for the Montaldo di Mondovì and Valletta samples, respectively. The mineral is orthorhombic, Pbcm, with single-crystal unit-cell parameters a = 8.8761(9), b = 7.5190(8), c = 11.689(1) Å and V = 780.1(1) Å3 (Montaldo di Mondovì sample) and a = 8.8889(2), b = 7.5269(1), c = 11.6795(2) Å, V = 781.43(2) Å3 (Valletta sample) with Z = 4. The seven strongest powder X-ray diffraction lines for the sample from Montaldo di Mondovì are [d Å (Irel; hkl)]: 4.85 (57; 102), 3.470 (59; 120, 113), 3.167 (100; 022), 2.742 (30; 310, 213), 2.683 (53; 311, 023), 2.580 (50; 222, 114) and 2.325 (19; 320, 214, 223). The crystal structure (R1 = 0.0250 for 1554 unique reflections for the Montaldo di Mondovì sample and 0.0260 for 3242 unique reflections for the Valletta sample) has MnO5(OH) octahedra forming edge-shared dimers; these dimers are connected through corner-sharing, forming two-up-two-down [[6]M2([4]TO4)4φ2] chains [M = Mn; T = As; φ = O(OH)] running along [001]. These chains are bonded in the a and b directions by sharing corners with AsO4 tetrahedra, giving rise to a framework of tetrahedra and octahedra hosting seven-coordinated Ca2+ and Na+ cations. The crystal structure of piccoliite is closely related to that of pilawite-(Y) as well as to carminite-group minerals that also show the same type of chains but with different linkage. The mineral is named after the mineral collectors Gian Paolo Piccoli and Gian Carlo Piccoli (father and son) (1926–1996 and b. 1953, respectively), the latter having discovered the type material at the Montaldo di Mondovì mine.

Pohlite, a new lead iodate hydroxide chloride from Sierra Gorda, Chile

AbstractThe new mineral pohlite (IMA2022–043), Pb7(IO3)(OH)4Cl9, was found at La Compania mine, Sierra Gorda, Antofagasta Province, Antofagasta, Chile, where it occurs in cavities in an oxidised portion of a quartz vein in association with massive aragonite and anhydrite. Pohlite crystals are transparent, colourless to pale grey blades, up to 4 mm in length. The mineral has a white streak, adamantine lustre and is nonfluorescent. It is brittle with irregular, conchoidal fracture. The Mohs hardness is ~2½ and it has no cleavage. The calculated density is 5.838(2) g cm–3. Optically, the mineral is biaxial (+) with α < 2.01(est.), β = 2.02 (calc.), γ = 2.05 (calc.); 2V = 60(5)°; moderate r > v dispersion; orientation: Y∧a ≈ 20°, Z∧b ≈ 30°; and is nonpleochroic. The Raman spectrum exhibits bands consistent with IO3– and O–H. Electron microprobe analysis provided the empirical formula Pb6.74I1.00Cl9.29O6.71H4.23. The five strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 3.818(91)(023, 122, 1$\bar{2}$1), 3.674(85)($\bar{1}\bar{2}$1, $\bar{1}$22, 200, 104), 3.399(47)($\bar{2}$10, 210, $\bar{1}$04), 2.378(100)(302, 041, $\bar{2}$24) and 1.9943(45)(multiple). Pohlite is triclinic, P$\bar{1}$, a = 7.3366(5), b = 9.5130(9), c = 16.2434(15) Å, α = 81.592(7), β = 84.955(7), γ = 89.565(6)°, V = 1117.13(17) Å3 and Z = 2. The structure of pohlite (R1 = 0.0328 for 3394 I > 2σI) contains two types of clusters, a [Pb4(OH)3]5+ cluster formed by short Pb–O bonds and a [Pb3(OH)(IO3)]28+ ‘double cluster’ formed by short I–O bonds and short- to medium-length Pb–O bonds. Long Pb–Cl and I–Cl bonds link the clusters together in three dimensions.

Oldsite, K2Fe2+[(UO2)(SO4)2]2(H2O)8, a new uranyl sulfate mineral from Utah, USA: its description and implications for the formation and occurrences of uranyl sulfate minerals

AbstractOldsite (IMA2021-075), ideally K2Fe2+[(UO2)(SO4)2]2(H2O)8, is a new uranyl sulfate mineral found on specimens from the North Mesa Mine group, Temple Mountain, San Rafael district, Emery County, Utah, USA. It is a secondary mineral occurring with alum-(K), halotrichite, metavoltine, quartz, römerite, stanleyite, sulphur, szomolnokite and mathesiusite. It forms rectangular blades flattened on {010} and elongated on [001], reaching ~0.3 mm in length. Crystals are yellow in colour, transparent with a vitreous lustre; the streak is very pale yellow. The mineral is non-fluorescent. Cleavage is excellent on {100} and perfect on {010}; the Mohs hardness is ~2. Crystals are brittle with irregular, splintery fracture. The density measured by flotation in a mixture of methylene iodide and toluene is 3.31 g⋅cm–3; the calculated density is 3.298 g⋅cm–3 for the empirical formula and 3.330 g⋅cm–3 for the ideal formula. Oldsite is biaxial (+), with α = 1.552(2), β = 1.556(2) and γ = 1.588(2) (measured in white light). The 2V measured directly on a spindle stage is 37(1)°; the calculated 2V is 39.6°. Dispersion is r < v, moderate. The optical orientation is X = b, Y = a and Z = c. The mineral is non-pleochroic. The empirical formula of oldsite (on the basis of 28 O apfu) is K1.93(Fe2+0.53Zn0.31V3+0.09Mg0.08)Σ1.02[(U0.98O2)(S1.01O4)2]2(H2O)8. The Raman spectrum is dominated by the vibrations of SO42– and UO22+ units. Oldsite is orthorhombic, Pmn21, a = 12.893(3), b = 8.276(2), c = 11.239(2) Å, V = 1199.2(5) Å3 and Z = 2. The five strongest powder X-ray diffraction lines are [dobs, Å (I, %) (hkl) ]: 8.29 (59) (010), 6.47 (82) (200), 5.10 (62) (210), 4.65 (100) (012, 211) and 3.332 (55) (022, 221). The crystal structure of oldsite was refined from single-crystal X-ray data to R = 0.0258 for 2676 independent observed reflections, with Iobs > 3σ(I). Oldsite is an Fe2+ analogue of svornostite; its crystal structure is based upon infinite chains of uranyl-sulfate polyhedra, which comprises pentagonal UO7 bipyramids sharing four of their equatorial vertices with sulfate tetrahedra such that each tetrahedron is linked to two uranyl bipyramids to form an infinite chain (the free, non-linking equatorial vertex of the uranyl bipyramid is an H2O group). The broader discussion on the origin and composition of uranyl sulfate minerals is made. The new mineral name honours American mineralogist, Dr. Travis A. Olds for his contribution to uranium mineralogy.

Scenicite, a new uranyl-sulfate mineral from the White Canyon district, San Juan County, Utah, USA

AbstractThe new mineral scenicite (IMA2021-057), [(UO2)(H2O)2(SO4)]2⋅3H2O, was found in the Green Lizard, Giveaway–Simplot, Markey and Scenic mines, White Canyon district, San Juan County, Utah, USA, where it occurs as a secondary phase on granular quartz matrix in association with various combinations of deliensite, gypsum, natrozippeite, rietveldite and shumwayite. Scenicite crystals are transparent, light green yellow, poorly formed blades or prisms, up to 0.1 mm in length. The mineral has white streak and vitreous lustre. It exhibits bright greenish-white fluorescence (405 nm laser). It is brittle with irregular, curved fracture and a Mohs hardness of ~2. It has excellent {100} and good {001} cleavages. The calculated density is 3.497 g cm–3. Optically, the mineral is biaxial (–) with α = 1.556(2), β = 1.573(2), γ = 1.576(2) (white light); 2V = 45(3)°; extreme r < v dispersion; orientation: X = c, Y = a, Z = b; pleochroism: X and Y = colourless, Z = light green–yellow; and X = Y < Z. The Raman spectrum exhibits bands consistent with UO22+, SO42– and O–H. Electron microprobe analysis provided the empirical formula U1.996S2.005O19H13.997. The five strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 7.69(70)(201), 5.63(100)(111), 4.92(84)(202,310), 4.80(93)(401) and 3.398(55)(020,120,511,601). Scenicite is orthorhombic, Pca21, a = 21.2144(15), b = 6.8188(3) c = 11.2554(6) Å, V = 1628.18(16) Å3 and Z = 4. In the structure of scenicite (R1 = 0.0365 for 1259 I > 2σI), linkages of pentagonal bipyramids and tetrahedra form an infinite neutral [(UO2)(SO4)(H2O)2] chain. The structure of shumwayite contains topologically identical chains.

Paradimorphite, β-As4S3, a vintage new mineral from Solfatara di Pozzuoli and Vesuvius, Napoli, Italy

AbstractThe new mineral paradimorphite corresponds to the high temperature polymorph of As4S3, whose existence was supposed by Arcangelo Scacchi in 1850 in the fumaroles at the Solfatara di Pozzuoli, Campi Flegrei, near Napoli, Italy.Crystals of paradimorphite are orange yellow, transparent or semitransparent, with adamantine lustre. Habit is prismatic and observed forms are {110}, {101}, {111}, {100}, {010} and {001}. Tenacity is brittle, no distinct cleavage is observed and fracture is conchoidal. The mineral does not fluoresce in long- or shortwave ultraviolet light. No twinning is apparent. The streak is saffron yellow. Hardness (Mohs) = 1–2. The observed density is 3.510(3) g/cm3, calculated density is 3.500 g/cm3. The mineral is orthorhombic, space group Pnma, with a = 9.1577(7), b = 8.0332(6), c = 10.2005(8) Å, V = 750.41(10) Å3 and Z = 4. The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 6.299(48)(011), 5.186(100)(111), 4.174(31)(201), 3.133(34)(022), 3.116(58)(212), 2.980(41)(122), 1.846 (27)(413) and 1.808(23)(134). The structure was refined to R = 0.0229 for 979 reflections with I >2σ(I). Crystals of paradimorphite contain As4S3 molecules, of idealised C3v symmetry, with the four arsenic atoms in a triangular pyramidal arrangement, with sulfur atom bridges on the three adjacent apical edges. Molecular dimensions and conformation are identical within standard uncertainties with those of the low-temperature polymorph dimorphite. No substantial differences, neither in the molecular packing nor in the molecular orientation, could be observed; minor differences being related to intermolecular distances only.

Guite, the spinel-structured Co2+Co3+2O4, a new mineral from the Sicomines copper–cobalt mine, Democratic Republic of Congo

AbstractGuite (IMA2017-080), Co3O4, is a new mineral species and an important economic mineral found in the Sicomines copper-cobalt mine, located ~11 km southwest of Kolwezi City, Democratic Republic of Congo. The mineral occurs as a granular agglomerate, 50 to 500 μm in size, and is associated closely with heterogenite in a quartz matrix. Guite is opaque, has a dark grey colour with metallic lustre and a black streak. In reflected light microscopy, it is white with no internal reflections. The reflectance values (in air,Rin %) are: 27.0 (470 nm); 25.6 (546 nm); 25.2 (589 nm), and 24.6 (650 nm). The average of 20 electron-microprobe analyses is Co 71.53, Cu 0.58, Mn 0.67, Si 0.25, O 26.78, total 99.82 wt.%, corresponding to the empirical formula calculated on the basis of 4 O apfu: (Co2+0.92Cu2+0.02Si4+0.02)Σ0.96(Co3+1.98Mn3+0.03)Σ2.01O4.00, with Co2+and Co3+partitioned using charge balance. The ideal formula is Co2+Co3+2O4. Guite is cubic with space groupFd$\bar{3}$m. The unit cell parameters refined from the single crystal X-ray diffraction data are:a= 8.0898(1) Å,V= 529.436(11) Å3andZ= 8. The calculated density of guite is 6.003 g/cm3. The eight strongest observed powder X-ray diffraction lines [din Å (I/I0) (hkl)] are: 4.6714 (16.7) (111), 2.8620 (18.4) (220), 2.4399 (100) (311), 2.3348 (10.4) (222), 2.0230 (24.8) (400), 1.5556 (26.3) (511, 333), 1.4296 (37.7) (440) and 1.0524 (10.1) (731, 553). The crystal structure of guite was determined by single-crystal X-ray diffraction and refined toR= 0.0132 for 3748 (69 unique) reflections. Guite has a typical spinel-type structure with Co2+in tetrahedral coordination with a Co2+–O bonding length of 1.941(1) Å, and Co3+in octahedral coordination with a Co3+–O bonding length of 1.919(1) Å. The structure is composed of cross-linked framework of chains of Co3+–O6octahedra sharing the equilateral triangle edges (2.550 Å) in three directions [0 1 1], [1 1 0], [1 0 1] with Co2+filling the tetrahedral interstices among the chains. Guite is named in honour of Prof. Xiangping Gu (1964–).

The new mineral tomiolloite, Al12(Te4+O3)5[(SO3)0.5(SO4)0.5](OH)24: A unique microporous tellurite structure

Abstract Tomiolloite (IMA2021-019) is a new aluminum tellurite sulfite-sulfate mineral discovered at the Bambolla mine, Moctezuma, Sonora, Mexico, a well-known tellurium (Te) mineral locality. Tomiolloite forms roughly spherical clusters of crystals comprised of very thin, needle-like crystals (1 μm diameter, ~40 μm length) around a core of small, stubbier, broken crystals. Tomiolloite is generally found growing on tellurite or quartz. The strongest powder X-ray diffraction lines are [dobs Å (Iobs) (hkl)]: 11.667 (89) (100), 8.240 (38) (101), 4.107 (29) (202,211,121), 3.223 (100) (203,302,130), and 2.905 (37) (213,123,222,400). The empirical formula of tomiolloite, as determined by electron microprobe analysis, is (Al10.64Te1.016+Fe0.313+Zn0.04)Σ12(Te5.004+Pb0.02)Σ5.02(S0.494+S0.496+Si0.02)Σ1.00O21.53[(OH)20.86Cl0.11]Σ20.97, which is simplified to the ideal formula Al12(Te4+O3)5[(SO3)0.5(SO4)0.5](OH)24. Significant Te6+ substitution for Al3+ is observed in tomiolloite, verified by X-ray photoelectron spectroscopy and crystal-structure analysis. The structure of tomiolloite was determined using synchrotron single-crystal X-ray diffraction, showing that tomiolloite is hexagonal and crystallizes in the space-group P63/m, with the unit-cell parameters a = 13.3360(19) Å, c = 11.604(2) Å, V = 1787.3(6) Å3, and Z = 2. Tomiolloite has a unique microporous framework structure, which bears a slight similarity to that of zemannite, but it has a much larger cavity diameter (8.85 Å). The framework is built from edge-sharing Mφ6 octahedra (M = Al3+ and Te6+), Te4+O3 trigonal pyramids, and Te4+O4 disphenoids. Mφ6 octahedra edge-share to form crankshaft-shaped chains along c, with Te4+On polyhedra filling notches in the crankshafts and providing linkages between adjacent chains. The framework has an overall positive charge, which is balanced by the presence of both sulfite (SO32−) trigonal pyramids and sulfate (SO42−) tetrahedra in the channels.

Hydroplumboelsmoreite, (Pb1□1)Σ2(W1.33Fe3+0.67)Σ2O6(H2O), a redefined mineral species of the elsmoreite group from China

AbstractHydroplumboelsmoreite (IMA21-C), (Pb,□)2(W,Fe3+)2O6(H2O), is a redefined elsmoreite-group mineral in the pyrochlore supergroup. It was found in a ‘jixianite’ cotype specimen provided by Mr. Liu Jianchang, who first found ‘jixianite’ in 1979 in the Jizhou District, Tianjin City, China. The mineral occurs as yellow to reddish brown aggregates, together with raspite and another elsmoreite-group mineral under study. Hydroplumboelsmoreite occurs in cryptocrystalline form and occasionally in octahedral microcrystalline form (under 20 μm in size). The crystals are colourless and translucent with a white streak, and the lustre is adamantine to greasy. Hydroplumboelsmoreite is isotropic, with a calculated refractive index of 2.29, a Mohs hardness of ~4½–5, and a calculated density of 7.47 g⋅cm−3. The strongest five powder X-ray diffraction lines [d in Å(I)(hkl)] are 6.070(28)(111), 3.012(100)(222), 2.603(32)(004), 1.836(35)(044) and 1.568(30)(226). The crystal structure was refined to R1 = 0.0459 using 80 unique reflections collected with MoKα radiation, and the results show that the mineral is cubic, space group Fd$\bar{3}$m, with a = 10.3377(5) Å, V = 1104.77(16) Å3 and Z = 8. Electron microprobe analyses and crystal structure refinement were used to determine the empirical formula: (Pb1.05Sr0.05Ce3+0.07Na0.01□0.82)Σ2.00(W1.32Fe3+0.67Zr0.01)Σ2.00O6[(H2O)0.43O0.19□0.38]Σ1.00. The mineral was named hydroplumboelsmoreite based on the predominance of Pb, W, and molecular H2O in the A, B and Y sites, respectively.