ALBERT

Description: Sejkoraite-(Y), the triclinic (Y1.98Dy0.24){sum}2.22H0.34+ [(UO2)8O88O7OH(SO4)4](OH)(H2O)26, is a new member of the zippeite group from the [C]ervena vein, Jachymov (Street Joachimsthal) ore district, Western Bohemia, Czech Republic. It grows on altered surface of relics of primary minerals: uraninite, chalcopyrite, and tennantite, and is associated with pseudojohannite, rabejacite, uranopilite, zippeite, and gypsum. Sejkoraite-(Y) forms crystalline aggregates consisting of yellow-orange to orange crystals, rarely up to 1 mm in diameter. The crystals have a strong vitreous luster and a pale yellow-to-yellow streak. The crystals are very brittle with perfect {100} cleavage and uneven fracture. The Mohs hardness is about 2. The mineral is not fluorescent either in short- or long-wavelength UV radiation. Sejkoraite-(Y) is yellow, with no visible pleochroism, biaxial negative with {alpha}' = 1.62(2), {beta}' = 1.662(3), {gamma}' = 1.73(1), 2Vcalc = 79{degrees}. The empirical chemical formula (mean of 8 electron microprobe point analyses) was calculated on the basis of 12 (S + U) atoms: (Y1.49Dy0.17Gd0.11Er0.07Yb0.05Sm0.02){sum}1.90H0.54 + [(UO2)8.19O7OH(SO4)3.81](H2O)26.00. Sejkoraite-(Y) is triclinic, space group P[IMG]f1.gif" ALT="Formula" BORDER="0"〉, a = 14.0743(6), b = 17.4174(7), c = 17.7062(8) A, {alpha} = 75.933(4), {beta} = 128.001(5), {gamma} = 74.419(4){degrees}, V = 2777.00(19) A3, Z = 2, Dcalc = 4.04 g/cm3. The seven strongest reflections in the X-ray powder diffraction pattern are [dobs in A (I) (hkl)]: 9.28 (100) (100), 4.64 (39) (200), 3.631 (6) ([IMG]f1.gif" ALT="Formula" BORDER="0"〉42), 3.451 (13) ([IMG]f1.gif" ALT="Formula" BORDER="0"〉44), 3.385 (10) ([IMG]f2.gif" ALT="Formula" BORDER="0"〉[IMG]f3.gif" ALT="Formula" BORDER="0"〉2), 3.292 (9) (044), 3.904(7) (300), 2.984 (10) ([IMG]f1.gif" ALT="Formula" BORDER="0"〉[IMG]f3.gif" ALT="Formula" BORDER="0"〉2). The crystal structure of sejkoraite-(Y) has been solved by the charge flipping method from single-crystal X-ray diffraction data and refined to Robs = 0.060 with GOFobs = 2.38, based on 6511 observed reflections. The crystal structure consists of uranyl sulfate sheets of zippeite anion topology, which alternate with an interlayer containing Y3+(H2O)n polyhedra and uncoordinated H2O groups. Two yttrium atoms are linked to the sheet directly via uranyl oxygen atom, and the remaining one is bonded by hydrogen bonds only. In the Raman and infrared spectrum of sejkoraite-(Y) there are dominating stretching vibrations of SO4 tetrahedra (~1200-1100 cm-1), UO22+ stretching vibrations (~900-800 cm-1), and O-H stretching (~3500-3200 cm-1) and H-O-H bending modes (~1640 cm-1). The new mineral is named to honor Ji[r]i Sejkora, a Czech mineralogist of the National Museum in Prague.

Description: Allanite-(Nd), ideally CaNdAl2Fe2+(SiO4)(Si2O7)O(OH), the Nd-analog of allanite-(Ce), occurs in the Åskagen pegmatite, central Sweden. It forms fine-grained aggregates within altered thalénite-(Y). The other associated minerals include: iimoriite-(Y), keiviite-(Y), allanite-(Y), and tengerite-(Y). Allanite-(Nd) is biaxial (−); with refractive indices α = 1.723(5), β = 1.754(7), γ = 1.772(5), and measured 2V = 82°(±3°). Larger fragments of allanite-(Nd) are moderately pleochroic (α = pale grayish-brown, γ = grayish-brown); small fragments are colorless. Allanite-(Nd) is monoclinic, space group P21/m, with the following unit-cell parameters: a = 8.8897(5), b = 5.7308(2), c = 10.1010(6) Å, β = 115.166(7)°, V = 465.75(4) Å3, Z = 2. The strongest five peaks from the X-ray powder diffraction patterns [d (Å)(I)(hkl)] are: 3.51(46)(2̄11), 2.89(100)(1̄13), 2.87(45)(020), 2.70(60)(120), 2.61(60)(3̄11). Allanite-(Nd) has a density of 3.98 g/cm3, vitreous luster, grayish-brown streak, and the Mohs hardness is ca. 6. It is brittle, with imperfect cleavage, and conchoidal fracture. The Mössbauer spectroscopy revealed Fe3+/Fetot ratio of 0.27 in the type sample. The refined empirical formula of the crystal used for the structure determination is: The allanite-(Nd) was approved by CNMNC (IMA 2010-060).

Description: The infrared (IR) spectra of gem-quality xenotime crystals containing considerable amounts of rare earth elements (REEs), are characterized by sharp and strongly pleochroic absorption bands in the 3650-3350 cm-1 region. In contrast, the spectra of partially metamict samples are dominated by a broad band centered at around 3450 cm-1. Xenotime presents the interesting case of a nominally anhydrous mineral, where the OH stretching frequency region of weakly hydrogen-bonded OH groups is overlapped by absorption bands due to low-energetic f-f electron transitions of REEs, especially of dysprosium. In polarized spectra measured parallel to the c-axis, Dy shows a prominent sharp band at 3519 cm-1. The assignment of the REE bands is based on the polarized IR spectra of REE doped xenotime single crystals, which have been synthesized by the flux method. A single band at 3480 cm-1, strongly polarized perpendicular to the c-axis, is assigned to the stretching vibration of an OH group. Deuteration experiments performed at 950 {degrees}C prove the assignment of this band and the presence of additional structural OH groups, appearing at annealing temperatures above 500 {degrees}C. Models of the OH point defect incorporation into the crystal structure of xenotime can be derived on the basis of fully occupied cation sites and under the assumption of Y- and P-site vacancies. The water content of the gem-quality samples ranges from 5 to 10 wt ppm and for the partially metamict samples from 370 wt ppm to 1.7 wt% H2O.

Description: The previously published structure determination of weeksite from the Anderson mine, Arizona, U.S.A., suggested that it is orthorhombic, Cmmb, with a = 14.209(2), b = 14.248(2), c = 35.869(4) Å, and V = 7262(2) Å3, and an ideal chemical formula (K,Ba)1–2(UO2)2(Si5O13)·H2O. Using single-crystal X-ray diffraction, electron microprobe analysis, and thermal analysis, we reexamined weeksite from the same locality. Our results demonstrate that weeksite is monoclinic, with the space group C2/m and unit-cell parameters a = 14.1957(4), b = 14.2291(5), c = 9.6305(3) Å, ß = 111.578(3)°, V = 1808.96(10) Å3, and an ideal formula K2(UO2)2(Si5O13)·4H2O. The previously reported orthorhombic unit cell is shown to result from twinning of the monoclinic cell. The structure refinement yielded R1 = 2.84% for 1632 observed reflections [Iobs 〉 3s(I)] and 5.42% for all 2379 reflections. The total H2O content derived from the structure refinement agrees well with that from the thermal analysis. Although the general topology of our structure resembles that reported previously, all Si sites in our structure are fully occupied, in contrast to the previous structure determination, which includes four partially occupied SiO4 tetrahedra. From our structure data on weeksite, it appears evident that the orthorhombic cell of the newly discovered weeksite-type mineral coutinhoite, ThxB1-2x(UO2)2Si5O13·3H2O, needs to be reevaluated.

Description: Adolfpateraite, monoclinic K(UO2)(SO4)(OH)(H2O), is a new supergene mineral from the Svornost mine, Jáchymov ore district, Czech Republic. It forms sulfur yellow to greenish yellow crystalline aggregates, up to 2 mm in diameter. Crystals are transparent to translucent with a vitreous luster, without observable cleavage. The streak is pale yellow. The Mohs hardness is ~2. The mineral shows a green fluorescence in long-wave ultraviolet radiation. Adolfpateraite is pleochroic, with a = colorless and ? = yellow (ß could not been examined). It is biaxial, with a = 1.597(2), ? = 1.659(2) (ß could not been measured), birefringence 0.062. The empirical chemical formula (mean of 4 electron microprobe point analyses) was calculated based on 8 O apfu and is K0.94(UO2)1.00(SO4)1.02(OH)0.90(H2O)1.00 (water content calculated). The simplified formula is K(UO2)(SO4)(OH)(H2O), requiring K2O 10.70, UO3 64.97, SO3 18.19, H2O 6.14, total 100.00 wt%. Adolfpateraite is monoclinic, space group P21/c, a = 8.0462(1), b = 7.9256(1), c = 11.3206(2) Å, ß = 107.726(2)°, V = 687.65(2) Å3, Z = 4, and Dcalc = 4.24 g/cm3. The five strongest reflections in the X-ray powder diffraction pattern are [dobs in Å (I) (hkl)]: 7.658 (76) (100), 5.386 (100) (002), 5.218 (85) (1¯02), 3.718 (46) (021), 3.700 (37) (2¯02). The crystal structure has been refined from single-crystal X-ray diffraction data to R1 = 0.0166 with GOF = 1.30, based on 1915 observed reflections [Iobs 〉 3s(I)]. The crystal structure consists of chains of uranyl polyhedra extended along [010], with OH- located on the shared vertex between the bipyramids. The sulfate tetrahedra decorate the outer side of the chain with bridging bidentate linkages between the uranyl pentagonal bipyramids. H2O groups are located on the edges of the chains on the non-linking vertex of each uranyl pentagonal bipyramid. K+ atoms are located between the chains providing additional linkage of these together with H-bonds. The fundamental vibrational modes of uranyl ion, sulfate tetrahedra, and H2O groups were tentatively assigned in the infrared and Raman spectra. The new mineral is named to honor Adolf Patera (1819–1894), Czech chemist, mineralogist, and metallurgist.

Description: Sakhaite, ca. Ca48Mg16(BO3)32(CO3)16(HCl,H2O)2, is a rare rock-forming borate-carbonate mineral typically occurring in high-temperature, low-pressure calcareous skarns. It forms a complete solid solution with harkerite, ca. Ca48Mg16[AlSi4(O,OH)16]4(BO3)16(CO3)16(HCl,H2O)2. The solid solution can be described with the general formula Ca48(Mg,Fe,Mn)16(CO3)16[AlaSi5−a(O,OH)16]y(BO3)32−4y(HCl,H2O)n where ymax = 8 and nmax = 16 – y. In this study, we examine samples of sakhaite and harkerite from four localities worldwide: Titovskoye deposit, Sakha Republic, Russia (type locality for sakhaite); Solongo B deposit, Buryatia Republic, Russia; Camas Malag, Skye, Scotland (type locality for harkerite); as well as a sakhaite-like mineral from the Kombat Mine, Tsumeb. The Si:B ratios of the samples ranged from that of end-member sakhaite (containing B only) to that of end-member harkerite (Si:B = 1:1), with several intermediate compositions. All samples were deficient in B relative to the ideal composition, implying significant substitution for borate groups. The Si:Al ratio of silicate-containing samples ranged from the ideal 4:1 to 4:1.5, implying substitution of Al at the Si site. The cubic unit-cell parameter was found to increase linearly with increasing Si content, except for the sakhaite-like mineral from Tsumeb. This mineral was found to have significant substitution of Pb for Ca (0.4–0.5 apfu) and was poor in Cl, which in most sakhaite and harkerite samples occupies the interstitial site surrounded by four borate groups. This interstitial site in the Tsumeb samples appears to be, instead, mainly occupied by H2O, which may qualify the mineral as a distinct species.

Description: Kroupaite (IMA 2017-031), ideally KPb0.5[(UO2)8O4(OH)10]·10H2O, is a new uranyl-oxide hydroxylhydrate mineral found underground in the Svornost mine, Jáchymov, Czechia. Electron-probe micro-analysis (WDS) provided the empirical formula (K1.28Na0.07)Σ1.35(Pb0.23Cu0.14Ca0.05Bi0.03Co0.02Al0.01)Σ0.48 [(UO2)7.90(SO4)0.04O4.04(OH)10.00]·10H2O, on the basis of 40 O atoms apfu. Sheets in the crystal structure of kroupaite adopt the fourmarierite anion topology, and therefore kroupaite belongs to the schoepite-family of minerals with related structures differing in the interlayer composition and arrangement, and charge of the sheets. Uptake of dangerous radionuclides (90Sr or 135Cs) into the structure of kroupaite and other uranyl-oxide hydroxy-hydrate is evaluated based on crystal-chemical considerations and Voronoi-Dirichlet polyhedra measures. These calculations show the importance of these phases for the safe disposal of nuclear waste.

Description: Smamite, Ca2Sb(OH)4[H(AsO4)2]·6H2O, is a new mineral species from the Giftgrube mine, Rauenthal, Sainte-Marie-Aux-Mines ore-district, Haut-Rhin department, France. It is a supergene mineral found in quartz-carbonate gangue with disseminated to massive tennantite-tetrahedrite series minerals, native arsenic, Ni-Co arsenides, and supergene minerals picropharmacolite, fluckite, and pharmacolite. Smamite occurs as lenticular crystals growing in aggregates up to 0.5 mm across. The new mineral is whitish to colorless, transparent with vitreous luster and white streak; non-fluorescent under UV radiation. The Mohs hardness iŝ3½; the tenacity is brittle, the fracture is curved, and there is no apparent cleavage. The measured density is 2.72(3) g/cm3; the calculated density is 2.709 g/cm3 for the ideal formula. The mineral is insoluble in H2O and quickly soluble in dilute (10%) HCl at room temperature. Optically, smamite is biaxial (–), α = 1.556(1), β = 1.581(1), γ = 1.588(1) (white light). The 2V (meas) = 54(1)°; 2V (calc) = 55.1°. The dispersion is weak, r > ν. Smamite is non-pleochroic. Electron microprobe analyses provided the empirical formula Ca2.03Sb0.97(OH)4[H1.10(As1.99Si0.01O4)2]·6H2O. Smamite is triclinic, P1–, a = 5.8207(4), b = 8.0959(6), c = 8.21296(6) Å, α = 95.8343(7)°, β = 110.762(8)°, γ = 104.012(7)°, V = 402.57(5) Å3, and Z = 1. The structure (Robs = 0.027 for 1518 I>3σI reflections) is based upon {Ca2(H2O)6Sb(OH)4[H(AsO4)2]} infinite chains consisting of edge-sharing dimers of Ca(H2O)3O2(OH)2 polyhedra that share edges with Sb(OH)4O2 octahedra; adjacent chains are linked by H-bonds, including one strong, symmetrical H-bond with an O–H bond-length of ∼1.23 Å. The name “smamite” is based on the acronym of the Sainte-Marie-aux-Mines district.