Table of Contents for the Journal of GEOsciences. List of articles from the latest print issue.https://www.jgeosci.orgen-US https://www.jgeosci.org/img-system/jgeosci_cover.jpghttps://www.jgeosci.org Plášil JK, Sejkora J; Vol. 70, issue 3, page: 117
]]> https://www.jgeosci.org/rss.php?ID=jgeosci.0054.25 Editorial https://www.jgeosci.org/rss.php?ID=jgeosci.0054.25 Plášil JK, Sejkora J; Vol. 70, issue 3, pages 119 - 137
]]> https://www.jgeosci.org/rss.php?ID=jgeosci.0050.25 Editorial https://www.jgeosci.org/rss.php?ID=jgeosci.0050.25 Števko M, Sejkora J, Ferenc Š; Vol. 70, issue 3, pages 139 - 150
A new occurrence of three rare supergene uranyl molybdates, calcurmolite, iriginite and umohoite was recently discovered at the Majerská valley U-Mo prospect near Čučma, Spišsko-gemerské rudohorie Mts., Slovakia. Calcurmolite is the most common uranyl molybdate at the studied locality, followed by relatively common iriginite and rare umohoite. In this paper, we present their detailed mineralogical study, including paragenetic observations, X-ray powder diffraction, chemical composition, and a Raman spectroscopic study. The quantitative chemical (WDS) data indicate a significant presence of Fe (around 0.35 apfu) in both iriginite and umohoite, whereas Na and K are typical minor elements observed in calcurmolite. The studied assemblage of supergene uranyl molybdates was formed by in-situ weathering of uraninite-molybdenite aggregates under the relatively acidic conditions, caused by breakdown of abundant pyrite and absence of carbonates. ]]> https://www.jgeosci.org/rss.php?ID=jgeosci.0043.25 Original paper https://www.jgeosci.org/rss.php?ID=jgeosci.0043.25 Kampf AR, Plášil J, Olds TA, Emproto C, Ma C, Sejkora J, Adams PM, Marty J; Vol. 70, issue 3, pages 151 - 161
Hubbardite (IMA 2025-041), Mg(H₂O)₆[(UO₂)₂O(OH)(SO₄)]₂·8H₂O, is a new zippeite-like mineral from the Hubbard Homestead mine, Mesa County, Colorado, USA. The new mineral occurs on sandstone matrix in close association with gypsum and an unknown Al-bearing uranyl-oxide hydroxy-hydrate. Hubbardite is orthorhombic, space group Fddd (#70), with unit cell parameters a = 8.8698(17), b = 34.183(7), c = 39.377(9) Å, V = 11939(4) ų and Z = 16. Crystals are plates up to about 0.3 mm in diameter, commonly forming subparallel or divergent aggregates. Crystals are flattened on {001} and exhibit the forms {100}, {001} and {140}. Hubbardite is yellow in color but sometimes appears dark brown, especially on edges. It has a pale-yellow streak and is nonfluorescent. It is transparent with vitreous luster. The mineral is flexible, but not elastic, and has a curved and stepped fracture. The Mohs hardness is about 2½. The measured density is 3.59(5) g/cm³. The mineral is optically biaxial (-), with α = 1.570(5), β = 1.625(5), γ = 1.646(5) (white light). The measured 2V is 62(2)°. Dispersion is r < v strong. The optical orientation is X = c, Y = b, Z = a, and the pleochroism is X light yellow, Y yellow, Z brownish yellow; X < Y < Z. The empirical formula is {(Mg_0.92□_0.08)_Σ1.00(H₂O)₆[(NH₄)_0.69(H₂O)_7.31]_Σ8.00}{(U_0.98O₂)₂[O_1.02(OH)_0.98]_Σ2.00(SO₄)]}₂based on O+N = 34 and S = 2 apfu. The crystal structure of hubbardite (R₁ = 0.0616 for 1348 reflections with I > 2σ_I) contains zippeite-type sheets between which are Mg(H₂O)₆ octahedra and isolated H₂O groups. ]]> https://www.jgeosci.org/rss.php?ID=jgeosci.0040.25 Original paper https://www.jgeosci.org/rss.php?ID=jgeosci.0040.25 Plášil J, Škoda R, Kampf AR, Němec I, Meisser N, Favreau G; Vol. 70, issue 3, pages 163 - 176
The new synthetic counterpart of a potentially new member of the svornostite group of minerals, “magnesiorietveldite”, ideally Mg(UO₂)(SO₄)₂(H₂O)₅, is orthorhombic, space group Pmn2₁, a = 12.7950(9), b = 8.3288(4), c = 11.2962(4) Å, V = 1203.80(11) ų and Z = 2. The crystal structure (R₁ = 0.0168 for 3113 I > 3σI reflections) contains uranyl-sulfate chains that are linked into sheets by M1O₂(H₂O)₄ and M2O₂(H₂O)₄ octahedra, where Mg is a dominant cation over Zn at both sites. The structure is well known and has already been described for other members of the svornostite group; the fundamental building unit - an infinite [(UO₂)(SO₄)₂(H₂O)]^2- chain is common in several uranyl minerals and synthetic compounds. Synthetic “magnesiorietveldite” was obtained after treatment of a specimen containing pitchblende with sulfuric acid. Electron microprobe analyses yielded the empirical formula (Mg_0.63Zn_0.22Cu_0.09Fe_0.05)_∑0.99(UO₂)(SO₄)₂·5H₂O, confirming the predominance of Mg over the other divalent cations. Infrared and Raman spectroscopy confirmed the presence of structurally non-equivalent molecular H₂O and sulfate tetrahedra. We append an extensive discussion on the role of molecular H₂O in the svornostite-group of minerals based on the bond-valence approach. ]]> https://www.jgeosci.org/rss.php?ID=jgeosci.0047.25 Original paper https://www.jgeosci.org/rss.php?ID=jgeosci.0047.25 Olds TA, Emproto C, Kampf AR, Ma C, Marty J; Vol. 70, issue 3, pages 177 - 188
Szilagyiite (IMA 2024-063), NaCa₃(UO₂)(CO₃)₃(SeO₃)F(H₂O)₆, is a new uranyl-carbonate-selenite mineral from the Pickett Corral mine, Montrose County, Colorado, USA. The new mineral occurs on sandstone and asphaltite matrix in close association with ferroselite, andersonite, schröckingerite, magselite, and an unidentified Na-Ca-uranyl carbonate-selenite-sulfate. Szilagyiite is trigonal, space group R3c (#161), with unit cell parameters a = 9.6542(9), c = 33.465(5) Å, V = 2701.2(6) ų and Z = 6. Crystals occur as dense yellow-green rosettes up to 1 mm wide and individual tablets up to ˜200 µm. Szilagyiite crystals are predominantly tabular on {001} and exhibit {001}, {00-1}, {102}, and {0-1-2} forms, with frequent twinning by inversion and perfect {001} cleavage. It has a pale yellow-green streak and fluoresces dimly green under longwave UV and 405 nm illumination, but has no apparent fluorescence under SWUV. Crystals are transparent with vitreous luster and exhibit a brittle, uneven fracture, with a Mohs hardness between 2-3. The calculated density based on the empirical formula is 3.17 g/cm³, and 3.16(2) g/cm³ as measured by flotation in a mixture of diiodomethane and toluene. The mineral is optically uniaxial (-), with ω = 1.628(2), ε = 1.538(2) measured in white light. It is pleochroic: O yellow, E colorless; O > E. The empirical formula is Na_0.76Ca_3.11(UO₂)(CO₃)₃(Se_1.16O₃)F_0.82O_20.18H_13.19 based on 21 O+F, U = 1, with C = 3 apfu based on the structure and H set to achieve charge balance. The eight strongest powder X-ray diffraction lines are [d_obs Å(I)(hkl)]: 5.916(100)(104), 4.836(58)(110), 3.744(77)(018), 3.125(33)(211,122), 2.960(60)(214), 2.795(62)(300), 1.828(40)(410) and 1.744(35)(238,146). The structure of szilagyiite (R₁ = 0.0314 for 2335 reflections with I > 2σI) is based on infinite sheets built from 3 major components: distorted cubane-like [(SeO₃)Ca₃(F,OH)(H₂O)₃] units, NaO₄(H₂O)₃ monocapped trigonal antiprisms, and hexagonal bipyramidal uranyl tricarbonate cluster units, [UO₂(CO₃)₃]. The sheets are cross-linked by a thin layer of hydrogen bonds formed between interlayer H₂O bound to Na, with F/OH, and O in the sheets. ]]> https://www.jgeosci.org/rss.php?ID=jgeosci.0049.25 Original paper https://www.jgeosci.org/rss.php?ID=jgeosci.0049.25 Koděra P, Majzlan J, Pollok K, Šimko F; Vol. 70, issue 3, pages 189 - 197
The new mineral vegrandisite (BaCl₂) was discovered at the porphyry gold deposit Biely Vrch, 3.5 km southeast of the town Detva, in the Central Slovak Volcanic Field. It occurs as a minor phase in salt melt inclusions hosted by vein quartz, where it forms small anhedral and transparent crystals up to 4 μm long, accompanied by halite and several other daughter minerals, mainly javorieite, rinneite, chlorocalcite and hibbingite. Vegrandisite was identified by techniques embedded in transmission electron microscopy but many mineral properties, including optical and structural ones, are known from the synthetic BaCl₂ analogue. Strongest bands in the Raman spectra include 114, 125, 187 cm^-1 and in the IR spectra in the region between 2852 and 2944 cm^-1. Vegrandisite in inclusions approaches the composition of BaCl₂, but Sr (up to ˜4.5 wt. %) and Br (up to ˜2.1 wt. %) are also incorporated. It is orthorhombic, belongs to the space group Pnma. Obtained unit-cell parameters a = 7.80(3) Å; b = 4.71(2) Å; c = 9.60(9) Å, V = 352.68 (54) ų are consistent with the published parameters of α-BaCl₂ that exhibits a PbCl₂-type (cotunnite) structure. Solid phases in salt melt inclusions, including vegrandisite, have crystallized from the salt melt on cooling of the inclusions. Late crystallization of BaCl₂ is related to accumulation of the incompatible element barium in the residual salt melt. Parental salt melt evolved from a hypersaline liquid, accompanied by a magmatic vapor, that were exsolved from a shallow dioritic magma. ]]> https://www.jgeosci.org/rss.php?ID=jgeosci.0035.25 Original paper https://www.jgeosci.org/rss.php?ID=jgeosci.0035.25