Journal of GEOsciences Table of Contents for the Journal of GEOsciences. List of articles from the latest print issue.http://www.jgeosci.orgen-US Journal of GEOsciences <![CDATA[ Foreword to the thematic set “New Minerals and Mineralogy in the 21st Century”. A thematic set arising from the international mineralogical symposium Jáchymov 2016 ]]> Plášil J, Laufek F; Vol. 62, issue 2, page: 77
Jáchymov (Joachimsthal), the famous mining centre connected with the 16th century silver rush in the Krušné hory (Erzgebirge) Mountains, discoveries of the new elements radium and polonium, and known for the famous radon spa, is one of the most interesting and the richest mineralogical localities in the World. In September 2016 this small town hosted a three-day international symposium dedicated to mineralogy and crystal chemistry of minerals, held under the name “New Minerals and Mineralogy in the 21st Century - Jáchymov 2016”. This symposium was symbolically organized on the occasion of the 500th anniversary of the town’s foundation. The quality and topics of the talks given during the conference motivated us to collect selected papers and compile this thematic set of the Journal of Geosciences. It presents four contributions focused on mineralogy and crystal chemistry of minerals. ]]> Editorial
<![CDATA[ Hydrogen bonding and structural complexity of the Cu3(AsO4)(OH)3 polymorphs (clinoclase, gilmarite): a theoretical study ]]> Krivovichev SV; Vol. 62, issue 2, pages 79 - 85
Density functional theory (DFT) is used to determine positions of H atoms and to investigate hydrogen bonding in the crystal structures of two polymorphs of Cu3(AsO4)(OH)3: clinoclase and gilmarite. Hydrogen bonds in clinoclase involve interactions between hydroxyl groups and O atoms of arsenate tetrahedra, whereas the crystal structure of gilmarite features OHOH bonding, which is rather uncommon in copper hydroxy-oxysalts. Information-based parameters of structural complexity for clinoclase and gilmarite show that the former is more complex (IG,total = 213.212 bits/cell) than the latter (IG,total = 53.303 bits/cell), which indirectly points out that gilmarite is metastable. This suggestion is supported by the lower density of gilmarite (4.264 g/cm3) compared to that of clinoclase (4.397 g/cm3). The hypothesis of metastable character of gilmarite is in agreement with the Goldsmith’s simplexity principle and the Ostwald-Volmer rule. ]]> Original Paper
<![CDATA[ New crystallographic data and formula revision of phuralumite, Al2[(UO2)3(PO4)2O(OH)](OH)3(H2O)9 ]]> Dal Bo F, Hatert F, Philippo S; Vol. 62, issue 2, pages 87 - 95
The crystal structure of phuralumite, Al2[(UO2)3(PO4)2O(OH)](OH)3(H2O)9, from the Kobokobo pegmatite (Kivu, Democratic Republic of Congo), was refined from single crystal X-ray diffraction data. Four samples have been investigated in this study, and the crystal structure was to R1 = 0.0566, 0.0544, 0.0661 and 0.0353, for 5739, 5953, 6007 and 5793 unique observed reflections, for the samples VC2048, VC2048, VC2054 and VC2055, respectively. Phuralumite is monoclinic, space group P21/n, a = 9.4407(3), b = 20.8596(8), c = 13.4326(4) Å, β = 107.905(4)°, V = 2517.40(17) Å3, and Z = 4 (sample VC2048). The structure consists of [(UO2)3(PO4)2O(OH)]3- layers, parallel to (010), which are connected by Al3+ ions and H2O molecules. The uranyl phosphate sheets show the phosphuranylite anion topology, while the Al3+ ions occur in 5- and 6-fold coordination and are connected together to form Al4O4(OH)6(H2O)4 clusters. The crystallographic data obtained from the four structural models converge and confirm the previously determined structure for phuralumite. However, these new data also show some discrepancies in the bond-valence analysis, especially in the assignment of the OH- groups and water molecules. As a consequence of this study, the structural formula of phuralumite, previously reported as Al2[(UO2)3(PO4)2(OH)2](OH)4(H2O)10, must be modified to Al2[(UO2)3(PO4)2O(OH)](OH)3(H2O)9. ]]> Original Paper
<![CDATA[ Crystal structure of the (REE)-uranyl carbonate mineral shabaite-(Nd) ]]> Plášil J, Škoda R; Vol. 62, issue 2, pages 97 - 105
Shabaite-(Nd) is a rare supergene mineral formed during alteration-hydration weathering of uraninite; its structure has remained unknown until now. Based on single-crystal X-ray diffraction data, shabaite-(Nd) is triclinic, twinned (leading to a pseudo-monoclinic diffraction pattern), space group P-1, with a = 8.3835(5), b = 9.2766(12), c = 31.7519(3) Å, α = 90.058(3), β = 89.945(4), γ = 90.331(4)°, V = 2469.3(4) Å3 and Z = 4. The structure was refined from diffraction data to R = 0.060 for 8434 unique observed reflections. The structure of shabaite-(Nd) is based upon finite clusters of polyhedra, the well-known uranyl-tricarbonate cluster (referred to as UTC), the Ca-polyhedra linked to UTC and infinite sheets of Nd-polyhedra with internal Nd-O-C linkages. The infinite sheets of Nd-polyhedra are stacked perpendicular to c; to the UTC are staggered approximately perpendicular to the Nd-based sheets (thus approx. parallel to c), forming electroneutral ({Nd3+2(CO3)2-2(H2O)2}2+{Ca(H2O)5}2+[(UO2)(CO3)3]4-)0 layers. Adjacent layers are linked by hydrogen bonds. The ratio of elements in the chemical formula of shabaite-(Nd), obtained from the structure refinement, Nd2Ca[(UO2)(CO3)3](CO3)2(H2O)10.5, Z = 4, was confirmed by an electron-microprobe study. The resulting empirical formula for the average of six point analyses is Ca1.01(Nd0.64Ce0.32Sm0.28Gd0.19Y0.19Pr0.13Dy0.10La0.07Tb0.05Ho0.01)Σ1.98(UO2)(CO3)4.98(H2O)10.5 (based on 1 U apfu). A discussion of the crystal-structural relationships of shabaite-(Nd) and chemically related minerals is given as well as discussion of complexities of their crystal structures. ]]> Original Paper
<![CDATA[ Rietveldite, Fe(UO2)(SO4)2(H2O)5, a new uranyl sulfate mineral from Giveaway-Simplot mine (Utah, USA), Willi Agatz mine (Saxony, Germany) and Jáchymov (Czech Republic) ]]> Kampf AR, Sejkora J, Witzke T, Plášil J, Čejka J, Nash BP, Marty J; Vol. 62, issue 2, pages 107 - 120
Rietveldite (IMA2016-081), Fe(UO2)(SO4)2·5H2O, is a new uranyl sulfate mineral described from three localities: Giveaway-Simplot mine (Utah, USA), Willi Agatz mine (Saxony, Germany) and Jáchymov (Western Bohemia, Czech Republic). The mineral rarely occurs in blades up to 0.5 mm long, in association with other post-mining supergene uranyl sulfates and U-free sulfates. Rietveldite is orthorhombic, space group Pmn21, a = 12.9577(9), b = 8.3183(3), c = 11.2971(5) Å, V = 1217.7(1) Å3 and Z = 4. Thin blades are elongated on [001] and flattened on {010}. Rietveldite is brownish yellow; powdery aggregates have yellowish beige color; and it has a white streak. It does not exhibit fluorescence under either long- or short-wave UV. It is transparent to translucent with a vitreous luster. Crystals are brittle, with curved fracture and Mohs hardness ˜2. Cleavage is good on {010}, and fair on {100} and {001}. Rietveldite is easily soluble in room-temperature H2O. The density is 3.31 g/cm3. Rietveldite is optically biaxial (+), with α = 1.570(1), β = 1.577(1) and γ = 1.586(1) (white light); 2Vcalc. = 83.3°, 2Vmeas. = 82(1)°. Dispersion is very strong (r > v). Rietveldite exhibits barely noticeable pleochroism in shades of light brownish yellow color, Y < XZ. The optical orientation is X = b, Y = a, Z = c. Chemical analyses for rietveldite from Giveaway-Simplot (WDS, 4 spots on 2 crystals) provided FeO 9.56, ZnO 1.06, MgO 0.14, MnO 0.10, SO3 26.99, UO3 47.32, H2O (calc.) 15.39, total 100.56 wt. %, which yields the empirical formula (Fe0.79Zn0.08Mg0.02Mn0.01)Σ0.90(UO2)0.99(SO4)2.01·5.10H2O (based on 15 O apfu). Prominent features in the Raman and infrared spectra include the O-H stretching vibrations, symmetric and antisymmetric stretching vibrations of (UO2)2+ ion, and stretching and bending vibrations of symmetrically non-equivalent (SO4)2- groups. The eight strongest powder X-ray diffraction lines are [dobs Å (Irel.) (hkl)]: 8.309(34)(010), 6.477(100)(200), 5.110(58)(210), 4.668(48)(012), 4.653(36)(211), 3.428(41)(013), 3.341(33)(221), 3.238(49)(400). The crystal structure of rietveldite (R1 = 0.037 for 2396 reflections with Iobs > 2σ[I]) contains infinite uranyl sulfate chains of composition [(UO2)(SO4)2(H2O)]2- along [001]. The adjacent chains are linked in the [100] direction by FeO6 octahedra, which share vertices with SO4 tetrahedra resulting in a heteropolyhedral sheet parallel to {010}; adjacent sheets are linked by hydrogen bonding only. The uranyl sulfate chains are the same as those in the structures of several other uranyl sulfate minerals. Rietveldite is named for Hugo M. Rietveld (1932-2016). ]]> Original paper
<![CDATA[ Carbonate-rich dyke in Roztoky Intrusive Complex - an evidence for carbonatite magmatism in the Eger Rift? ]]> Rapprich V, Kochergina YV, Magna T, Laufek F, Halodová P, Bůzek F; Vol. 62, issue 2, pages 121 - 136
The possible presence of carbonatites in the Eger Rift (NW Bohemian Massif, Czech Republic) has been debated for several decades without any apparent resolution. Here, we document an almost 2 m thick dyke of a silicocarbonatite (23 wt. % SiO2, 27 wt. % CO2) in the R2 (Roztoky nad Labem) drilling at the depth of 152.9-154.8 m. Despite the fact that the silicocarbonatite is associated with alkaline intrusive complex, its content of alkalis is rather low (Na2O + K2O = 2.5 wt. %), as are REE ((ΣREE = 82.6 ppm). The stable-isotope signature (δ18O = 7.43 ‰, (δ13C = −2.46 ‰) of this rock is distinct from surrounding sedimentary rocks, while it can be compared with C-O isotope systematics of some carbonatites in the world which probably sourced carbonates from older subduction events. The Sr-Nd isotope composition (87Sr/86Sr30 ˜ 0.7062; 143Nd/144Nd30 ˜ 0.51205) points to an enriched reservoir without known counterparts among alkaline rocks from the Eger Rift, perhaps a lithospheric mantle modified in course of the Variscan subduction. The position of the R2 silicocarbonatite in the Sr-Nd space may indicate a continuum of enriched radiogenic isotope systematics in worldwide carbonatite occurrences. ]]> Original paper
<![CDATA[ Polytypism of cronstedtite from Chyňava, Czech Republic ]]> Hybler J, Sejkora J; Vol. 62, issue 2, pages 137 - 146
Small druses and isolated crystals of cronstedtite in cavities of a quartz-calcite veinlet were encountered in the borehole drilled near Chyňava (central Bohemia, Czech Republic) in 1943-1944. Single crystals were studied by the X-ray diffraction with aid of the four circle diffractometer with an area detector. The interpretation of precession-like images of reciprocal lattice planes produced by the diffractometer software revealed the polytype 2H1 (of the subfamily - Bailey’s group D) as the most abundant. It occurs either as pure or mixed crystals with minor to negligible proportion of the 2H2 polytype of the same subfamily. Lattice parameters of both polytypes are: a = 5.4907(3), c = 14.1789(9) Å, space groups P63cm (2H1), and P63 (2H2). A crystal of the polytype 3T (subfamily A), twinned by reticular merohedry was sparingly found as well. Another unusual mixed crystal of subfamilies C+A contained the 1T polytype (subfamily C), a disordered portion of the subfamily A except for the apical part of the crystal, and small amount of 3T and possible traces of 6T2 polytypes (subfamily A) in the bottom part. Electron probe microanalysis of selected cronstedtite crystals revealed minor amounts of Cl up to 0.01 apfu (atoms per formula unit), and small amounts of Mg (0.13-0.24 apfu) regardless of the determined polytype. ]]> Original paper