Brittle Tenacity Research Articles

Karlseifertite, Pb(Ga2Ge)(AsO4)2(OH)6, a new dussertite-group mineral, from Tsumeb, Namibia

Abstract. Karlseifertite (IMA 2024-007, International Mineralogical Association), Pb(Ga2Ge)(AsO4)2(OH)6, is a new member of the dussertite group, from Tsumeb, Namibia. It is a secondary oxidation-zone mineral found on fracture surfaces in germanite–chalcocite ore. Karlseifertite occurs in rosettes of thin, yellow, hexagonal plates up to about 0.2 mm in diameter and usually less than 0.01 mm thick. The mineral has a pale-yellow streak, subadamantine lustre, Mohs hardness of ∼ 4, brittle tenacity, irregular fracture, perfect cleavage on {001} and a calculated density of 4.993 g cm−3. Optically, karlseifertite crystals are uniaxial (+), with ω=1.890(5) and ε=1.894(calc) (white light). The empirical formula from electron probe microanalyses is Pb0.992+(Ga1.603+Ge0.684+Fe0.573+Al0.123+)Σ2.97[(As0.765+S0.156+W0.096+)Σ1.00O4]2(OH0.99)6. Karlseifertite is trigonal with space group R3‾m and unit-cell parameters a=7.2814(7), c=17.1077(12) Å, V=785.50(15) Å3 and Z=3. The mineral has an alunite-supergroup structure (R1=0.0591 for 248 reflections with I>2σI).

Rotherkopfite, KNa2(Fe2+2.5Ti4+1.5)Fe2+(Si4O12)2, a new neptunite-group mineral without essential lithium, from Rother Kopf, Eifel volcanic fields, Germany

Abstract. Rotherkopfite, KNa2(Fe2.52+Ti1.54+)Fe2+(Si4O12)2, is a new member of the neptunite group, from Rother Kopf, Roth, near Gerolstein, Eifel volcanic fields, Rhineland-Palatinate, Germany. It is found in cavities in a quartz–sanidine xenolith embedded in a vesicular alkaline basalt and is associated with fluorophlogopite and an amphibole supergroup mineral that is zoned from potassic-magnesio-fluoro-arfvedsonite on the exterior to potassic-fluoro-richterite in the core. It is presumed to have formed as the result of contact metasomatism of the xenolith by the alkaline basalt melt. Rotherkopfite occurs as brownish-red equant or tabular crystals, up to about 0.2 mm in maximum dimension. The mineral has a light-orange streak, a vitreous lustre, a Mohs hardness of ∼4.5, a brittle tenacity, a curved fracture and a density of 3.20(2) g cm−3. Optically, rotherkopfite crystals are biaxial (+), with α=1.668(5), β=1.678(5), γ=1.720(5) (white light) and 2V(meas) = 53.2(6)°. The empirical formula from electron microprobe analyses, secondary ion mass spectrometry and structure refinement is (K0.87Na0.20)Σ1.07(Na1.99Ca0.01)Σ2.00M1+M2(Fe1.662+Ti1.48Mg0.79Mn0.02)Σ3.95M3(Fe0.642+Li0.16Ti0.15Al0.01)Σ0.96(Si8.00O24). Rotherkopfite is monoclinic with space group C2/c and unit-cell parameters a=16.4599(17), b=12.5457(6), c=10.0487(7) Å, β=115.669(7)°, V=1870.3(3) Å3 and Z=4. The crystal structure (R1=0.0268 for 1324 reflections with I>2σI) is based on two interwoven three-dimensional frameworks: (1) a silicate framework made up of pyroxene-like chains of corner-sharing SiO4 tetrahedra and (2) an octahedral framework made up of chains of edge-sharing metal–oxygen octahedra. The two interwoven frameworks are bound to one another by corner sharing. K and Na are hosted in channels in the combined framework.

Perchiazziite, Co2(CO3)(OH)2, a New Member of the Rosasite–Malachite Group from the Monte Ramazzo Mine, Italy

ABSTRACT Perchiazziite, ideally Co2(CO3)(OH)2, is a new mineral discovered at the Monte Ramazzo Mine, Genova Province, Liguria, Italy. It occurs as globular aggregates up to 0.1 mm in diameter, composed of very thin fibers. These develop on a matrix composed mostly of goethite and magnetite, in association with calcite and Co-bearing malachite. Aggregates of perchiazziite are pale orange-pink on their outer surfaces but white in thin section. It is translucent with white streak, silky luster, brittle tenacity, and uneven fracture. No cleavage and parting are observed. The Mohs hardness is ∼4. Dcalc. = 3.970 g/cm3. The mean refractive index calculated using the Gladstone-Dale equation is 1.77. The main bands in the Raman spectrum are at 154, 511, 707, 1085, 1526, 3304, aXnd 3479 cm−1. The chemical composition (by electron microprobe; CO2 and H2O by stoichiometry) of perchiazziite is (in wt.%): MgO 1.81, CaO 0.41, MnO 0.32, FeO 0.12, CoO 32.45, NiO 4.02, CuO 5.40, ZnO 25.60, CO2 20.63, H2O 8.42, total 99.18. The empirical formula calculated on the basis of 5 O apfu is: (Co0.93Zn0.67Cu0.15Ni0.12Mg0.10Ca0.02Mn0.01)Σ2.00(CO3)(OH)2. The crystal structure was refined by the Rietveld method. Perchiazziite is monoclinic, space group P21/a, a = 12.1832(16) Å, b = 9.3187(16) Å, c = 3.1570(3) Å, β = 97.165(15)°, V = 355.62(8) Å3, and Z = 4. The strongest lines of the X-ray powder diffraction pattern [d, Å (I, %) (hkl)] are 6.040 (22) (200), 5.073 (38) (210), 3.694 (53) (220), 2.599 (100) (021), 2.535 (26) (420), 2.480 (27) (221̄), 2.140 (26) (231̄), 1.561 (25) (202̄). Perchiazziite is a new member of the rosasite–malachite group.

Désorite, Pb2(Fe3+6Zn)O2(PO4)4(OH)8, a New Phosphate Mineral Isotypic with Jamesite

The new mineral désorite, Pb2(Fe3+6Zn)O2(PO4)4(OH)8, is a secondary oxidation-zone mineral discovered on the dumps of the Schöne Aussicht mine, Dernbach, Westerwaldkreis, Rhineland-Palatinate, Germany. The crystals are irregular blades up to about 0.25 mm long, occurring in subparallel and radial aggregates. Désorite is brownish red. It has an orange streak, adamantine luster, brittle tenacity, splintery and curved fracture and two cleavages: {021¯} perfect and {001} good. It has a hardness (Mohs) of about 3 and is nonfluorescent in both long- and short-wave ultraviolet illumination. The calculated density is 4.633 g/cm3. Optically, crystals are biaxial (+) with α = 2.00(1), β = 2.02(calc) and γ = 2.10(calc) (white light). The 2V is 54(2)° and the optical orientation is Y ~⊥{021¯}, X ∧ a ≈ 13°. The mineral is pleochroic: X yellow brown, Y red brown, Z red brown; X < Y ≈ Z. The empirical formula from electron microprobe analysis is Pb1.93(Zn0.50Fe3+6.29☐0.21)Σ7.00(P3.90As0.10)Σ4.00O26H8.28. Désorite is triclinic, space group P1¯; the unit-cell parameters are a = 5.4389(7), b = 9.3242(13), c = 10.0927(12) Å, α = 109.024(8), β = 90.521(6), γ = 97.588(7)°, V = 478.90(11) Å3 and Z = 1. Désorite has a framework structure (R1 = 0.0487 for 937 I > 2σI reflections) assembled from Fe3+O6 octahedra and PO4 tetrahedra, with Pb occupying cavities in the framework. The Fe3+O6 octahedra in the framework occur in edge-sharing chains, edge-sharing trimers and individual octahedra, all sharing corners with each other and with PO4 tetrahedra. Désorite is isostructural with jamesite and lulzacite.

Plumboperloffite, PbMn2+2Fe3+2(PO4)3(OH)3, a new member of the bjarebyite group from Wiperaminga Hill, South Australia, Australia

AbstractPlumboperloffite, PbMn2+2Fe3+2(PO4)3(OH)3, is a new mineral and member of the bjarebyite group from Wiperaminga Hill West Quarry, Boolcoomatta Reserve, Olary Province, South Australia, Australia. The mineral was found in a single cavity in triplite–barbosalite matrix associated with fluorapatite, phosphosiderite, natrodufrénite and fluorite. The mineral forms intergrowths of subparallel, thin tabular to bladed crystals. Individual crystals are up to 40 μm in length. Plumboperloffite is brownish orange in colour with a vitreous lustre. The mineral has brittle tenacity, an excellent cleavage on {100} and uneven fracture. The calculated density is 4.416 g/cm3. Plumboperloffite is biaxial (+), α = 1.87(1), β = 1.88(1) and γ = 1.89(1) as measured in white light. The measured 2V is 88(1)°. Dispersion is apparently strong, based on extinction colours and the orientation is Y = b. The pleochroism in shades of yellow brown is X < Z < Y. Electron microprobe analysis gave the empirical formula (based on 15 O apfu) (Pb0.92Ca0.04Ba0.01K0.01)Σ0.98(Mn2+1.84Fe2+0.13)Σ1.97(Fe3+1.97Al0.03)Σ2.00(P3.01O11.94)(OH)Σ3.06. Plumboperloffite is monoclinic, space group P21/m with a = 9.1765(18), b = 12.340(3), c = 5.0092(10) Å, β = 101.01(3)°, V = 556.8(2) Å3 and Z = 2. The crystal structure has been refined using X-ray single-crystal data to a final R1 = 0.0207 on the basis of 1417 reflections with Fo > 4σ(Fo). The mineral is isostructural with members of the bjarebyite-group minerals.

Trebiskyite, the First Titanium-Decavanadate Mineral

Abstract Trebiskyite, Na3Mg2[TiV9O28]·22H2O, from the Pickett Corral mine, Bull Canyon, Montrose County, Colorado, USA, is the first mineral containing essential Ti as a component of a decavanadate polyanion. Crystals are thin prisms or needles up to ∼0.3 mm in length, occurring as individuals and in divergent sprays. Trebiskyite crystals are translucent yellow with vitreous luster and pale-yellow streak and are non-fluorescent under both longwave and shortwave ultraviolet illumination. The crystals exhibit elongation on [001] and are modified by several 0kl prism forms, possibly corresponding to {010}, {011}, and {012}. The Mohs hardness is ca. 2 based on scratch tests. Crystals have brittle tenacity with irregular fracture. No apparent cleavage, nor twinning, was evident, and the mineral is readily soluble in H2O. The density measured by flotation in methylene iodide-toluene mixture is 2.38(2) g/cm3. The calculated density is 2.352 g/cm3 for the empirical formula and 2.343 g/cm3 for the ideal formula. Electron microprobe analyses provided the empirical formula Na3.39Mg1.87V8.75Ti1.25O50H44.00, based on Ti + V = 10 apfu, O = 50 apfu, with the Na content having been determined from the refined crystal structure. Trebiskyite is monoclinic, space group P21/c, a = 9.478(4), b = 21.426(11), c = 11.267(5) Å, β = 114.572(7)°, V = 2080.8(13) Å3, Z = 2. The structure was refined from 6642 reflections to a final R1 = 0.0517 for reflections I > 2σ(I). The structural unit of trebiskyite, (TiV9O28)7−, is built from a Ti-substituted decavanadate polyanion, (V10O28)6−, found in other members of the pascoite family. Chemically, trebiskyite is closely related to lasalite, Na2Mg2[V10O28]·20H2O, and huemulite, Na4Mg[V10O28]·24H2O; however, trebiskyite contains a novel structural arrangement that is unique among the decavanadate minerals. The interstitial complex in trebiskyite has the ideal formula {[Na3Mg2(H2O)19](H2O)3} and consists of chains of distorted octahedrally coordinated Na+ and regular Mg[O(H2O)5] octahedra. The observed low incident bond valence to the V1 site (4.45 vu) and marked deviation in vanadyl and V–Oeq bond lengths indicate that this site is host to the essential Ti4+ identified during chemical analyses.

Shinkolobweite, from the Shinkolobwe Mine, Democratic Republic of Congo: A New Mineral Containing Uranium in the Rare Pentavalent Oxidation State

ABSTRACT Shinkolobweite, Pb1.333[U5+O(OH)(UO2)5O4.67(OH)5.33](H2O)5, is a new lead uranyl oxide-hydroxide hydrate mineral containing hexavalent and pentavalent uranium from the Shinkolobwe mine, Democratic Republic of Congo. Crystals of shinkolobweite are dark reddish-brown prisms up to 0.5 mm in length, occurring on a matrix of massive uraninite associated with fourmarierite, rutherfordine, soddyite, and sklodowskite. Crystals are translucent with subadamantine luster and light bronze-yellow streak, are flattened on {010}, are elongated on [001], and exhibit the forms {100}, {010}, {101}, and . The mineral is non-fluorescent under both longwave and shortwave ultraviolet illumination. It has a Mohs hardness of ∼2 and exhibits brittle tenacity with perfect cleavage on {010}, imperfect cleavage on {100}, and even fracture. The calculated density is 5.853 g/cm3 based on the empirical formula. Electron probe microanalysis provided the empirical formula Pb1.290U6+4.876U5+1.166O27H16.633 based on 27 O apfu and U5+:U6+ determined by X-ray photoelectron spectroscopy. Shinkolobweite is orthorhombic, superspace group Pnnm(0b0)000, a = 14.4808(4), b = 7.0681(8), c = 11.9423(3) Å, V = 1222.32(15) Å3, modulation wave vector [0 1/3 0], and Z = 2. The structure was refined from 8959 reflections to a final R1 = 0.0736 for all reflections. Uranyl oxide-hydroxide sheets in shinkolobweite adopt the β-U3O8 topology and possess (3 + 1) commensurately modulated ordering that results from the long-range ordering of U5+ and U6+ in the sheet, as well as the position and occupancy of interlayer Pb2+ cations. Observations of a topological transition between α-U3O8 and β-U3O8 type sheets in shinkolobweite supplements our understanding of U5+ mineral oxidation and stability.

Scandio-winchite, ideally ☐(NaCa)(Mg4Sc)(Si8O22)(OH)2: The first Sc-dominant amphibole-supergroup mineral from Jordanów Śląski, Lower Silesia, southwestern Poland

Abstract Scandio-winchite, the first natural Sc-dominant amphibole-supergroup mineral, has been discovered in a granitic pegmatite that crops out in close association with rodingite-like calc-silicate rocks and metasomatized granitic bodies in a serpentinite quarry at a Jordanów Śląski village near Sobótka, ~30 km south of Wrocław, Lower Silesia, SW Poland. It occurs as an isolated subhedral crystal, with the size of ~20 × 8 μm in planar section, and as three polycrystalline aggregates, up to 50 μm across, composed of needle-shaped crystals dominated by {110}. It is present within chlorite aggregates that supposedly represent remnants of partly recrystallized xenoliths of the blackwall chlorite schists and is in quartz-feldspar portions of the pegmatite adjoining such xenolithic assemblages. Owing to the scarcity of the material and the exceptionally small size of the crystals, the color, streak, and optical properties could not be measured. By analogy with other amphiboles, scandio-winchite has a vitreous luster, brittle tenacity, and a Mohs hardness of ~5½. The mineral shows an uneven fracture and {110} perfect cleavage, with an angle of ~56° between cleavage planes. The density calculated from the empirical formula and refined unit-cell parameters is 3.026 g/cm3. The holotype crystal is composed of (in wt%): 55.88 SiO2, 0.11 TiO2, 0.53 Al2O3, 9.22 Sc2O3, 0.44 MnO, 8.89 FeO, 12.77 MgO, 5.71 CaO, 4.12 Na2O, 0.17 K2O, and 2.09 H2Ocalc(+); total 99.93. The composition normalized on the basis of 22 O2– + 2 (OH)– ions corresponds to the empirical formula A(☐0.966K0.031Na0.003)Σ1B(Na1.132 Ca0.868)Σ2C(Mg2.704Fe1.0552+Mn0.053Sc1.140Al0.023Ti0.012)Σ4.987T(Si7.935Al0.065)Σ8.000O22(OH)2, simplified formula (☐,K)(Na,Ca)2[(Mg,Fe)4Sc](Si8O22)(OH)2, and the ideal formula ☐(NaCa)(Mg4Sc)(Si8O22)(OH)2. The crystal structure was refined in the monoclinic system, space-group symmetry C2/m, with R1 index of 6.57%. Its unit-cell parameters are: a = 9.864(2) Å, b = 18.163(3) Å, c = 5.3053(16) Å, β = 104.41(3)°, V = 920.6(4) Å3; Z = 2, and the a:b:c ratio is 0.5431:1:0.2921. The crystal-structure refinement indicates almost exclusively Si-occupied T sites, the M4 sites occupied by nearly equal amounts of Na and Ca, M1 and M3 sites by divalent Mg + Fe cations, and M2 filled in equal proportions by divalent cations and Sc. These results, along with the dominant vacancy at the A site, univocally indicate that the mineral corresponds to a M2Sc-analog of winchite. Scandio-winchite is most likely a secondary phase of metasomatic origin related to the evolution of the country rocks and partial alteration of the blackwall chlorite schists xenolith induced by the pegmatitic melt and associated fluids.

Fluoralforsite, Ba5(PO4)3F – a new apatite-group mineral from the Hatrurim Basin, Negev Desert, Israel

AbstractFluoralforsite, ideally Ba5(PO4)3F, (space group P63/m (#176), Z = 2, a = 10.0031(2) Å, c= 7.5382(2) Å and V = 653.23(3) Å3), is a new mineral species of the apatite group – a Ba-analogue of fluorapatite and a F-analogue of alforsite. It was discovered in rankinite paralava filling cracks in pyrometamorphic gehlenite hornfels near the tributary of wadi Zohar and Gurim Anticline, Hatrurim Basin, Negev Desert, Israel. Fluoralforsite occurs in small intergranular spaces between large gehlenite and garnet crystals and in enclaves inside large rankinite crystals with other Ba minerals such as walstromite, zadovite, bennesherite, gurimite, mazorite, barioferrite and baryte. It forms tiny transparent, colourless crystals up to 50 μm with a white streak and a vitreous lustre. The cleavage was not observed. It exhibits a brittle tenacity and a conchoidal fracture. The estimated Mohs hardness is 4–4½, and its calculated density is 4.57 g/cm–3. Fluoralforsite is uniaxial (–) with refractive indices (589 nm) nω = 1.689(3) and nɛ = 1.687(3). The empirical crystal-chemical formula for the holotype calculated on the basis of 8 cations is: (Ba3.81Ca0.97Na0.07K0.05Sr0.05Fe0.05)Σ5(P5+2.32V5+0.29S6+0.22Si0.17)Σ3O12(F0.85Cl0.13)Σ0.98. The crystal structure was refined from single-crystal X-ray diffraction data with R1 = 0.0192. The structural investigation indicated an ordered arrangement of Ba/Ca at the M1 site within individual columns running along the c-axis, but a disordered distribution among adjacent columns throughout the structure, which enables the maintenance of the P63/m space group. Fluoralforsite was formed at the final stage of crystallisation as a result of a reaction between the primary mineral assemblages and residual melt.

Chenowethite, Mg(H2O)6[(UO2)2(SO4)2(OH)2]·5H2O, a New Mineral with Uranyl-Sulfate Sheets from Red Canyon, Utah, USA

The new mineral chenowethite, Mg(H2O)6[(UO2)2(SO4)2(OH)2]·5H2O, was found in efflorescence crusts on tunnel walls at the Blue Lizard, Green Lizard and Markey uranium mines in Red Canyon, San Juan County, Utah, USA. The crystals are long, thin blades up to about 0.5 mm long, occurring in irregular sprays and subparallel groups. Chenowethite is pale green yellow. It has white streak, vitreous to silky luster, brittle tenacity, splintery and stepped fracture and two cleavages: {010} perfect and {001} good. It has a hardness (Mohs) of about 2 and is nonfluorescent in both long- and short-wave ultraviolet illumination. The density is 3.05(2) g/cm3. Optically, crystals are biaxial (−) with α = 1.530(2), β = 1.553(2) and γ = 1.565(2) (white light). The 2V is 72(2)° and dispersion is r > v (slight). The optical orientation is X = b, Y = a, Z = c and the mineral exhibits weak pleochroism in shades of pale green yellow: X < Y < Z. The Raman spectrum is consistent with the presence of UO22+, SO42− and OH–/H2O. The empirical formula from electron microprobe analysis and arranged in accordance with the structure is (Mg0.71Fe2+0.09Co0.05Ni0.04)∑0.89(H2O)6[(UO2)2(SO4)2(OH)2]·[(H2O)4.78(NH4)0.22]∑5.00. Chenowethite is orthorhombic, space group Cmcm; the unit-cell parameters are a = 6.951(2), b = 19.053(6), c = 16.372(5) Å, V = 2168.19(7) Å3 and Z = 4. The crystal structure of chenowethite (R1 = 0.0396 for 912 I > 2σI reflections) contains [(UO2)2(SO4)2(OH)2]2− sheets that are topologically equivalent to those in deliensite, feynmanite, greenlizardite, johannite, meitnerite and plášilite.

Amgaite, Tl3+2Te6+O6, a New Mineral from the Khokhoyskoe Gold Deposit, Eastern Siberia, Russia

The new mineral amgaite was discovered at the Khokhoyskoe gold deposit, 120 km W of Aldan town, Aldanskiy District, Sakha Republic (Yakutia), Eastern Siberia, Russia. Amgaite forms fine-grained colloform aggregates up to 0.05 mm across, and is often intimately intergrown with avicennite, unidentified carbonates and antimonates of Tl. Other associated minerals include gold, silver, acanthite, arsenopyrite, pyrite, berthierite, chalcocite, weissbergite, chlorargyrite, calcite, quartz, goethite etc. Amgaite is dark reddish brown to black. It has submetallic luster, black streak, brittle tenacity and conchoidal fracture. Its density calculated from the empirical formula and powder XRD data is 8.358 g/cm3. Its Mohs’ hardness is ca. 1.5–2. Optically, amgaite is uniaxial. In reflected light, it is gray with a bluish shade, very weakly anisotropic with rare brownish red internal reflections. Reflectance values for the four COM wavelengths [Rmin, Rmax (%)(λ in nm)] are: 13.5, 14.2 (470); 12.7, 13.2 (546); 12.3, 12.7 (589); and 11.7, 12.3 (650). The Raman spectrum shows bands of Te–O and Tl–O bonds and confirms the absence in amgaite of H2O, OH–, CO32– groups and B–O bonds. The chemical composition is (electron microprobe, wt.%): MgO 0.43, CaO 1.62, Fe2O3 0.36, Tl2O3 66.27, Sb2O5 3.48, TeO3 27.31, total 99.47. The empirical formula based on 6 O apfu is Tl3+1.74Ca0.17Mg0.06Fe3+0.03Te6+0.93Sb5+0.13O6. Amgaite is trigonal, space group P321; unit-cell parameters are as follows: a = 9.0600(9), c = 4.9913(11) Å, V = 354.82(8) Å3, Z = 3. The strongest lines of the powder X-ray diffraction pattern [dobs, Å (I, %) (hkl)] are as follows: 3.352 (100) (111), 3.063 (15) (201), 2.619 (49) (300), 2.065 (18) (221), 1.804 (28) (302), 1.697 (8) (321), 1.625 (9) (411). The crystal structure of amgaite is the same as of synthetic Tl3+2Te6+O6. The new mineral is named after the Amga River, the basin of which hosts the type locality, Khokhoyskoe occurrence. The type material is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia, with the registration number 5773/1.

Gismondine-Sr, Sr4(Al8Si8O32)·9H2O, a new strontium dominant, orthorhombic zeolite of the gismondine series from the Hatrurim Complex, Israel

Abstract A new mineral, gismondine-Sr with ordered gismondine framework type [B2212 no. 20, Z = 1; a = 14.0256(2) Å, b = 10.45900(10) Å, c = 13.79360(10) Å, V = 2023.44(4) Å3] and the ideal chemical formula Sr4(Si8Al8O32)·9H2O was discovered in amygdaloidal voids of partly melted gehlenite hornfels at Halamish locality, Hatrurim Basin of the Hatrurim Complex, Negev Desert, Israel. Gehlenite horn-fels is mainly composed of gehlenite, wollastonite, and garnet of the grossular-andradite-schorlomite series. In a low-temperature association occur minerals such as thomsonite-Ca, flörkeite, analcime and minerals of the tobermorite supergroup. Gismondine-Sr forms spherulitic aggregates up to 180 μm and, rarely, pseudotetragonal bipyramidal crystals up to 50 μm. Empirical crystal-chemical formula of gismondine-Sr is (Sr2.02Ca1.09Ba0.02K0.72Na0.62)Σ4.47Al7.91Si8.09O31.85·9H2O. It is the strontium analog of gismondine-Ca and the second orthorhombic zeolite with the GIS structure topology. Crystals are transparent to translucent and feature vitreous luster. The mineral exhibits a white color, imperfect cleavage in [101] direction, a brittle tenacity, and uneven fracture. The Mohs hardness was estimated at approximately 4. Gismondine-Sr is biaxial negative, α = 1.488(3), β = 1.492(3), γ = 1.495(3), 2Vobs = 70–80°. The Raman spectrum is characterized by a band at 465 cm−1, which is also the main band in gismondine-Ca. The structure refinement using SC-XRD (R1 = 0.0353) reveals the ordered distribution of framework cations and the disordered arrangement of extraframework cations. The aluminosilicate framework is built by crankshaft chains with 8-membered apertures channels parallel to [101] and [101]. In gismondine-Sr, the 8-membered rings are elliptically deformed and the T-O-T angle of the upward and downward tetrahedra in the double crankshaft chains is smaller compared to that for gismondine-Ca. Consequently, a slight rotation of the double crankshaft chains has been noticed. Similar observations have been made in partially dehydrated and the pressure-modified gismondine-Ca. The present study suggests that, in addition to high-pressure and dehydration, the elliptical deformation of the channels in GIS also arises as a consequence of the extraframework cations and H2O content. Thus, the extraframework content influences the aluminosilicate framework leading to the orthorhombic symmetry.

Nitscheite, (NH4)2[(UO2)2(SO4)3(H2O)2]·3H2O, a new mineral with an unusual uranyl-sulfate sheet

Abstract Nitscheite (IMA2020-078), (NH4)2[(UO2)2(SO4)3(H2O)2]·3H2O, is a new mineral species from the Green Lizard mine, Red Canyon, San Juan County, Utah, U.S.A. It is a secondary phase found in association with chinleite-(Y), gypsum, pyrite, and Co-rich rietveldite. Nitscheite occurs in subparallel and divergent intergrowths of yellow prisms, up to about 0.3 mm in length. Crystals are elongated on [101] and exhibit the forms {100}, {010}, {001}, and {111}. The mineral is transparent with vitreous luster and very pale-yellow streak. It exhibits bright green fluorescence under a 405 nm laser. The Mohs hardness is ~2. The mineral has brittle tenacity, curved fracture, and one good cleavage on {010}. The measured density is 3.30(2) g·cm−3. The mineral is easily soluble in H2O at room temperature. The mineral is optically biaxial (–), α = 1.560(2), β = 1.582(2), γ = 1.583(2) (white light); 2Vmeas = 17(1)°; no dispersion; orientation X = b, Z ≈ [101]; pleochroism X colorless, Y and Z yellow; X < Y ≈ Z. Electron microprobe analysis provided the empirical formula (NH4)1.99U2.00S3.00O21H10.01. Nitscheite is monoclinic, P21/n, a = 17.3982(4), b = 12.8552(3), c = 17.4054(12) Å, β = 96.649(7)°, V = 3866.7(3) Å3, and Z = 8. The structure (R1 = 0.0329 for 4547 I > 3σI reflections) contains [(UO2)2(SO4)3(H2O)2]2− uranyl-sulfate sheets, which are unique among minerals, with NH4 and H2O groups between the sheets.

Protocaseyite, a new decavanadate mineral containing a [Al4(OH)6(H2O)12]6+ linear tetramer, a novel isopolycation

Abstract Protocaseyite, [Al4(OH)6(H2O)12][V10O28]·8H2O, is a new mineral (IMA2020-090) occurring in low-temperature, post-mining, secondary mineral assemblages at the Burro mine, Slick Rock district, San Miguel County, Colorado, U.S.A. Crystals of protocaseyite are saffron-yellow, thick blades, with pale orange-yellow streak, vitreous luster, brittle tenacity, curved fracture, two very good cleavages, a Mohs hardness of 2, and a density of 2.45(2) g/cm3. The optical properties of protocaseyite could be only partly determined: biaxial with α = 1.755(5), β < 1.80, γ > 1.80 (white light); pleochroic with X and Y yellow, Z orange (X ≈ Y < Z). Electron-probe microanalysis and crystal-structure solution and refinement provided the empirical formula [(Al3.89Mg0.11Ca0.02)Σ4.02(OH)6(H2O)12][H0.06V10O28]·8H2O. Protocaseyite is triclinic, P1, a = 9.435(2), b = 10.742(3), c = 11.205(3) Å, α = 75.395(7), β = 71.057(10), γ = 81.286(6)°, V = 1036.4(5) Å3, and Z = 1. The crystal structure (R1 = 0.026 for 4032 Io>2 σI reflections) contains both the [V10O28]6− decavanadate polyoxoanion and a novel [Al4(OH)6(H2O)12]6+ polyoxocation.

Bennesherite, Ba2Fe2+Si2O7: A new melilite group mineral from the Hatrurim Basin, Negev Desert, Israel

AbstractThe first barium member of the melilite group, bennesherite Ba2Fe2+Si2O7 [P421m, Z = 2, a = 8.2334(14) Å, c = 5.2854(8) Å, V = 359.29(13) Å3], was discovered in thin veins of rankinite paralava within pyrometamorphic gehlenite hornfels at Gurim Anticline, Hatrurim Basin, Negev Desert, Israel. Bennesherite occurs in small intergranular spaces between large crystals of rankinite, gehlenite, and garnet together with other Ba-minerals such as fresnoite, walstromite, zadovite, gurimite, hexacelsian, and celsian. It forms transparent, light yellow to lemon-colored crystals with a white streak and a vitreous luster. They exhibit good cleavage on (001), a brittle tenacity, and a conchoidal fracture. The estimated Mohs hardness is 5. Bennesherite has a melilite-type structure with the layers composed of disilicate (Si2O7)6− groups and (Fe2+O4)6− tetrahedra, connected by large eightfold-coordinated Ba atoms. In some grains, epitaxial intergrowths of bennesherite and fresnoite are observed. The structure of the fresnoite, Ba2TiO(Si2O7) with a P4bm space group and unit-cell parameters a = 8.5262(5) Å, c = 5.2199(4) Å, is closely related to the structure of bennesherite. Among all the known minerals of the melilite group, bennesherite has a structure characterized by the lowest misfit degree between the tetrahedral (T1 and T2 sites) and polyhedral (X-site) layers, as it was shown in both natural and synthetic melilite-type phases.

Seaborgite, LiNa6K2(UO2)(SO4)5(SO3OH)(H2O), the First Uranyl Mineral Containing Lithium

Abstract Seaborgite (IMA2019-087), LiNa6K2(UO2)(SO4)5(SO3OH)(H2O), is a new mineral species from the Blue Lizard mine, Red Canyon, San Juan County, Utah, U.S.A. It is a secondary phase found on gypsum in association with copiapite, ferrinatrite, ivsite, metavoltine, and römerite. Seaborgite occurs in sprays of light-yellow, long flattened prisms or blades, up to about 0.2 mm in length. Crystals are elongated on [100], flattened on {010}, and exhibit the forms {100}, {010}, {001}, and {101}. The mineral is transparent with vitreous luster and very pale-yellow streak. It exhibits bright lime-green fluorescence under a 405 nm laser. The Mohs hardness is ~2½. The mineral has brittle tenacity, curved or conchoidal fracture, and one good cleavage on {100}. The measured density is 2.97(2) g/cm3. The mineral is immediately soluble in H2O at room temperature. The mineral is optically biaxial (–), α = 1.505(2), β = 1.522(2), γ = 1.536(2) (white light); 2Vmeas = 85(1)°; moderate r < ν dispersion; orientation X ^ a ≈ 10°; pleochroic X colorless, Y and Z light green-yellow; X < Y ≈ Z. EPMA and LA-ICP-MS analyses of seaborgite undermeasured its Li, K, and Na. The empirical formula using Li, Na, and K based on the structure refinement is Li1.00Na5.81K2.19(UO2)(SO4)5(SO3OH)(H2O). Seaborgite is triclinic, P1, a = 5.4511(4), b = 14.4870(12), c = 15.8735(15) Å, α = 76.295(5), β = 81.439(6), γ = 85.511(6)°, V = 1203.07(18) Å3, and Z = 2. The structure (R1 = 0.0377 for 1935 I = 2σI) contains [(UO2)2(SO4)8]4– uranyl-sulfate clusters that are linked into a band by bridging LiO4 tetrahedra. The bands are linked through peripheral SO4 tetrahedra forming a thick heteropolyhedral layer. Channels within the layers contain a K site, while an additional K site, six Na sites, and an SO3OH group occupy the space between the heteropolyhedral layers.

Jeankempite, Ca5(AsO4)2(AsO3OH)2(H2O)7, a new arsenate mineral from the Mohawk Mine, Keweenaw County, Michigan, USA

AbstractJeankempite, 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) Å3andZ= 3. The final structure was refined toR1= 0.0591 for 2781 reflections withIobs> 3σI. The crystal structure of jeankempite is built from a network of edge- and vertex-sharing CaO6, CaO7and AsO4polyhedra, and we hypothesise that the new mineral has formed due to a topotactic reaction brought on by dehydration of preexisting guérinite.

Jasonsmithite, a new phosphate mineral with a complex microporous framework, from the Foote mine, North Carolina, U.S.A

Abstract Jasonsmithite (IMA2019-121), Mn42+ZnAl(PO4)4(OH)(H2O)7·3.5H2O, is a pegmatite-phosphate mineral from the Foote Lithium Company mine, Kings Mountain district, Cleveland County, North Carolina, U.S.A. It is interpreted as having formed by late-stage, low-temperature hydrothermal alteration. Crystals are colorless to light brown, slightly flattened prisms to about 1 mm in length with wedge-shaped terminations. The mineral is transparent with vitreous luster, white streak, Mohs hardness 2, brittle tenacity, irregular fracture, and perfect {001} cleavage. The density is 2.63(2) g/cm3. Jasonsmithite is biaxial (–), with α = 1.561(2), β = 1.580(2), γ = 1.581(2), measured in white light. The 2V is 25(5)° and dispersion is r < ν moderate. The optical orientation is Y = b, X ^ c = 18° in obtuse β. The Raman spectrum is dominated by vibrational modes of PO4 and ZnO4 tetrahedra, AlO6 and MnO6 octahedra, and OH groups. Electron microprobe analyses gave the empirical formula (Mn3.09Fe0.87)Σ3.96Zn1.05Al0.98(PO4)4(OH)(H2O)7·3.5H2O. The mineral is monoclinic, P21/c, a = 8.5822(3), b = 13.1770(6), c = 20.3040(14) Å, β = 98.485(7)°, V = 2271.0(2) Å3, and Z = 4. The structure (R1 = 0.0443 for 3685 I>2σI reflections) contains zigzag chains of edge-sharing MnO6 octahedra that corner-link to adjacent chains and to PO4 tetrahedra to form sheets, which are decorated by ZnO4 tetrahedra. The sheets are linked to one another via dimers of AlO6 octahedra, forming a framework with large channels containing H2O groups. With H2O groups removed, the framework has a void space of 70.2% per unit cell, and a framework density of 14.5 polyhedral atoms/1000 Å3, which would place jasonsmithite among the most porous minerals.

Fehrite, MgCu4(SO4)2(OH)6 · 6H2O, the magnesium analogue of ktenasite from the Casualidad mine near Baños de Alhamilla, Almeria, Spain

The new mineral fehrite (IMA 2018-125a), MgCu4(SO4)2(OH)6 · 6H2O, is a member of the ktenasite group andthe Mg-analogue of ktenasite, ZnCu4(SO4)2(OH)6 · 6H2O. The mineral was found in the Casualidad mine near Baños deAlhamilla, Almeria, Spain, in association with clinoatacamite, kapellasite, gordaite, serpierite, connellite and gypsum.The transparent turquoise-coloured mineral has a vitreous lustre, exhibits a pale blue-green streak and shows distinctpleochroism. It forms radial aggregates of thin lath-like crystals of up to 200 μm in length. Fehrite is not fluorescent. Themonoclinic crystals show a perfect cleavage parallel to {001}. The mineral has a brittle tenacity and an uneven fracture. Thecalculated density is 2.73 g/cm3, the calculated mean refractive index is 1.584. The strongest lines observed in the X-raypowder diffraction pattern are [d in Å/Irel in %/(hkl)] 11.94/100/002, 5.92/31/004, 2.66/12/202, 4.85/11/013, 3.93/11/006and 2.96/10/008. The chemical composition, measured by means of an electron probe micro-analyser, was determined at(wt.%): MgO 5.31, MnO 0.49, CuO 33.12, ZnO 11.48, SO3 26.01, H2Ocalc. 24.63, total 101.04. The empirical formula basedon 20 O pfu., including 6(OH) and 6(H2O), is Mg0.87Cu2.74Zn0.93Mn0.05S2.14O8(OH)6 · 6H2O. The simplified end memberformula is MgCu4(SO4)2(OH)6 · 6H2O which requires MgO 5.92, CuO 46.74, SO3 23.52, H2O 23.82, total 100.00 (wt.%).Fehrite is monoclinic with space group P21/c (#14). Unit cell parameters determined by X-ray single crystal diffraction area = 5.6062(8), b = 6.1294(11), c = 23.834(3) Å, β = 95.29(1)º, V = 815.5(2) Å3, Z = 2. The mineral is isotypic with ktenasitewith Mg in place of Zn. The name is for the late Karl Thomas Fehr (1954 – 2014), Professor of Mineralogy at the Departmentof Geo- and Environmental Sciences at the Ludwig-Maximilians-University Munich, Germany.

Northstarite, a new lead-tellurite-thiosulfate mineral from the North Star mine, Tintic, Utah, USA

ABSTRACTNorthstarite, Pb6(Te4+O3)5(S2O3), is a new mineral from the North Star mine, Tintic district, Juab County, Utah, USA. It is an oxidation-zone mineral occuring in a vug in massive quartz-baryte-enargite-pyrite in association with anglesite, azurite, chrysocolla, fluorapatite, plumbogummite, tellurite, zincospiroffite, and the new mineral adanite. Crystals are beige short prisms with pyramidal terminations, up to about 1 mm in length. The mineral is transparent to translucent with adamantine luster, white streak, Mohs hardness 2, brittle tenacity, irregular fracture, and no cleavage. The calculated density is 6.888 g/cm3. Northstarite is uniaxial (–) and nonpleochroic. The Raman spectrum is consistent with the presence of tellurite and thiosulfate groups and the absence of OH and H2O. Electron-microprobe analyses gave the empirical formula Pb5.80Sb3+0.05Te4+5.04S6+1.02S2–1.02O18. The mineral is hexagonal, space group P63, with a = 10.2495(5), c = 11.6677(8) Å, V = 1061.50(13) Å3, and Z = 2. The five strongest X-ray powder diffraction lines are [dobs Å(I)(hkl)]: 3.098(100)(113), 2.957(88)(300), 2.140(42)(223), 1.7335(41)(413), and 1.6256(31)(306). The structure (R1 = 0.033 for 1476 I > 2σI reflections) is a framework constructed of short (strong) Pb–O and Te–O bonds with channels along the 63 axes. The thiosulfate groups at the centers of the channels are only weakly bonded to the framework.