V O Almazjuvelirexport

Moscow, Russia

V O Almazjuvelirexport

Moscow, Russia
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Plasil J.,Fyzikalni ustav AV CR v.v.i. | Hlousek J.,U Rohacovych kasaren 24 | Kasatkin A.V.,V O Almazjuvelirexport
Bulletin Mineralogicko-Petrologickeho Oddeleni Narodniho Muzea v Praze | Year: 2014

An interesting association of supergene U and Y/REE minerals was found in the dump material at the Dušní (Geister) vein in the Jáchymov ore district, Czech Republic. The mineral assemblage is represented by anomalously rich and well-crystalline metatyuyamunite associated with metazeunerite and minerals of the mixite group (agardite-(Y) and goudeyite), jarosite and probably chenevixite. Chemical composition of the metatyuyamunite studied was determined by electron microprobe analyses. Its empirical formula can be expressed as (Ca0.81Pb0.22)Σ1.03(U0.98O2)2V2.05O8.3H2O (mean of 5 point analyses; on the basis of 15 O and 3H2O apfu). Microprobe data indicated that the studied metatyuyamunite represents a Pb-rich variety, which is the first report so far. The refined unit-cell parameters of metatyuamunite from the powder X-ray diffraction data (for the orthorhombic space group Pman) are a = 10.615(8), b = 8.399(5), c = 16.824(5) Å with V = 1500(1) Å3. Minerals of the mixite group are represented by intermediate members of the agardite-(Y)-goudeyite solid solution series. Their empirical formula can be expressed as [(Y0.47Nd0.06)ΣREE0.53Al0.42Pb0.10Ca0.04)]Σ1.09(Cu5.92Zn0.06)Σ5.98 As2.99O12(OH)6·3H2O (agardite-(Y)) and [Al0.50(Y0.40Nd0.03)ΣREE0.43Pb0.08Ca0.04)]Σ1.05(Cu5.81Zn0.21)Σ6.02As2.98O12(OH)6·3H2O (goudeyite). Minerals of the mixite group, metytyuyamunite and namely metazeunerite are partly overgrown by jarosite and probable chenevixite. Studied association represents a supergene alteration products of in-situ weathering of primary ore mineralization. © 2014, National Museum Prague. All rights reserved.

Plasil J.,ASCR Institute of Physics Prague | Kampf A.R.,Natural History Museum of Los Angeles County | Kasatkin A.V.,V O Almazjuvelirexport | Marty J.,5199 E. Silver Oak Rd.
Journal of Geosciences (Czech Republic) | Year: 2014

Bluelizardite (IMA 2013-062), Na7(UO2)(SO 4)4Cl(H2O)2, is a new uranyl sulfate mineral from the Blue Lizard mine, San Juan County, Utah (USA). It was found in a sandstone matrix and is associated with chalcanthite, copiapite, ferrinatrite, gypsum, kröhnkite, johannite, and several other new, unnamed Na- and Mg-containing uranyl sulfates. Bluelizardite is a supergene mineral formed by the post-mining weathering of uraninite. The mineral is monoclinic, C2/c, with a = 21.1507(6), b = 5.3469(12), c = 34.6711(9) Å, β = 104.913(3)̊, V = 3788.91(17) Å3 and Z = 8. Crystals are blades up to 0.4 mm long, flattened on {001}, elongated parallel to [010] and exhibiting the forms {100}, {001} and {111}. Bluelizardite is pale yellow and has a yellowish-white streak. It has good cleavage on {001} and uneven fracture. The Mohs hardness is estimated at 2. The calculated density based on the empirical formula is 3.116 g/cm3. Bluelizardite exhibits bright yellow-green fluorescence under both long- and short-wave UV radiation. The mineral is optically biaxial (-), with a = 1.515(1), β = 1.540(1) and γ = 1.545(1) (measured with white light). The measured 2V is 48(2)̊ and the calculated 2V is 47.6̊. The mineral does not exhibit any dispersion or pleochroism. The optical orientation is X = b, Y ̃ a, Z ̃ c*. The empirical formula of bluelizardite is Na6.94(U1.02O2)(SO4)4.00Cl0.94O0.06(H2O)2 (based on 21 anions pfu). The Raman spectrum is dominated by the symmetric stretching vibrations of the uranyl (UO2 2+) group and sulfate tetrahedra and by the O-H stretching and bending vibrations of the H 2O molecules. The eight strongest powder X-ray diffraction lines are [dobs Å(I )(hkl) ]: 17.08(52)(002), 10.31(60)(200), 5.16(100)(mult.), 4.569(22)(402,-114), 4.238(23)(-115, 310, 008), 3.484(27)(-602,-604,- 2·0·10), 3.353(28)(mult.), 3.186(36)(mult.). The crystal structure of bluelizardite (R1 = 0.016 for 4268 reflections with Iobs > 3sI) is topologically unique among known structures of uranyl minerals and inorganic compounds. It is based upon clusters of uranyl pentagonal bipyramids and sulfate tetrahedra. Two uranyl pentagonal bipyramids are linked through the two vertices of SO4 groups. The remaining three vertices of each UO7 bipyramid are occupied by SO4 groups, linked monodentately. The eight independent Na+ cations are linked through the Na-O bonds along with hydrogen bonds (involving H⋯O and H⋯Cl bonds) into a 3D framework.

Plasil J.,ASCR Institute of Physics Prague | Veselovsky F.,Czech Geological Survey | Hlousek J.,U Rohacovych kasaren 24 | Skoda R.,Masaryk University | And 5 more authors.
American Mineralogist | Year: 2014

Mathesiusite, K5(UO2)4(SO4) 4(VO5)(H2O)4, a new uranyl vanadate-sulfate mineral from Jáchymov, Western Bohemia, Czech Republic, occurs on fractures of gangue associated with adolfpateraite, schoepite, čejkaite, zippeite, gypsum, and a new unnamed K-UO2-SO 4 mineral. It is a secondary mineral formed during post-mining processes. Mathesiusite is tetragonal, space group P4/n, with the unit-cell dimensions a = 14.9704(10), c = 6.8170(5) Å, V = 1527.78(18) Å3, and Z = 2. Acicular aggregates of mathesiusite consist of prismatic crystals up to ∼200 μm long and several micrometers thick. It is yellowish green with a greenish white streak and vitreous luster. The Mohs hardness is ∼2. Mathesiusite is brittle with an uneven fracture and perfect cleavage on {110} and weaker on {001}. The calculated density based on the empirical formula is 4.02 g/cm3. Mathesiusite is colorless in fragments, uniaxial (-), with ω = 1.634(3) and ε = 1.597(3). Electron microprobe analyses (average of 7) provided: K2O 12.42, SO 3 18.04, V2O5 4.30, UO3 61.46, H2O 3.90 (structure), total 100.12 (all in wt%). The empirical formula (based on 33 O atoms pfu) is: K4.87(U0.99O 2)4(S1.04O4)4(V 0.87O5)(H2O)4. The eight strongest powder X-ray diffraction lines are [dobs in Å (hkl) I rel]: 10.64 (110) 76, 7.486 (200) 9, 6.856 (001) 100, 6.237 (101) 85, 4.742 (310) 37, 3.749 (400) 27, 3.296 (401) 9, and 2.9409 (510) 17. The crystal structure of mathesiusite was solved from single-crystal X-ray diffraction data and refined to R1 = 0.0520 for 795 reflections with I > 3σ(I). It contains topologically unique heteropolyhedral sheets based on [(UO2)4(SO4)4(VO5)] 5-clusters. These clusters arise from linkages between corner-sharing quartets of uranyl pentagonal bipyramids, which define a square-shaped void at the center that is occupied by V5+ cations. Each pair of uranyl pentagonal bipyramids shares two vertices of SO4 tetrahedra. Each SO4 shares a third vertex with another cluster to form the sheets. The K+ cations are located between the sheets, together with a single H2O group. The corrugated sheets are stacked perpendicular to c. These heteropolyhedral sheets are similar to those in the structures of synthetic uranyl chromates. Raman spectral data are presented confirming the presence of UO2 2+, SO4, and molecular H 2O.

PlaSIl J.,ASCR Institute of Physics Prague | Kasatkin A.V.,V O Almazjuvelirexport | SKoda R.,Masaryk University | Skacha P.,Mining Museum Pribram | Skacha P.,Charles University
Mineralogical Magazine | Year: 2014

Klajite, MnCu4(AsO4)2(AsO3OH)2(H2O)10, the Mn-Cu-bearing member of the lindackerite group, was found in Jáchymov, Czech Republic, as the second world occurrence. It is associated with ondrus?ite and other arsenate minerals growing on the quartz gangue with disseminated primary sulfides, namely tennantite and chalcopyrite. Electron-microprobe data showed klajite aggregates to be chemically inhomogeneous at larger scales, varying from Mn-Ca-rich to Cu-rich domains. The chemical composition of the the Mn-rich parts of aggregates can be expressed by the empirical formula (Mn0 . 4 6Ca0 . 2 2Cu0 . 07Mg0 . 0 2 )S 0 . 7 7(Cu3 . 8 2Mg0 . 1 4Ca0 . 0 3Zn0 . 0 1 ) S4 . 00(As1 . 94Si0 . 06)S 2 . 0 0 O8[AsO2.73(OH)1.27]2(H 2O)10 (mean of seven representative spots; calculated on the basis of As + Si + P = 4 a.p.f.u. (atoms per formula unit) and 10 H2O from ideal stoichiometry), showing a slight cationic deficiency at the key Me-site. According to single-crystal X-ray diffraction, klajite from Jáchymov is triclinic, P1- , with a = 6.4298(8), b = 7.9716(8), c = 10.707(2) Å , a = 85.737(12)°, b = 80.994(13)°, g = 84.982(10)°, and V = 538.85(14) Å 3, Z = 1. The crystal structure was refined to R1 = 0.0628 for 1034 unique observed reflections (with Iobs > 3s(I)), confirming that klajite (Mn-Cu member) and ondrus?ite (Ca-Cu member) are isostructural. The current data-set allowed determination of the positions of several hydrogen atoms. Discussion on hydrogen bonding networks in the structure of klajite as well as detailed bond-valence analysis are provided. © 2014 The Mineralogical Society.

Kampf A.R.,Natural History Museum of Los Angeles County | Marty J.,5199 E. Silver Oak Road | Nash B.P.,University of Utah | Plasil J.,ASCR Institute of Physics Prague | And 2 more authors.
Mineralogical Magazine | Year: 2012

Calciodelrioite, ideally Ca(VO3)2(H 2O)4, is a new mineral (IMA 2012-031) from the uranium-vanadium deposits of the eastern Colorado Plateau in the USA. The type locality is the West Sunday mine, Slick Rock district, San Miguel County, Colorado. The new mineral occurs on fracture surfaces in corvusite- and montroseite-impregnated sandstone and forms as a result of the oxidative alteration of these phases. At the West Sunday mine, calciodelrioite is associated with celestine, gypsum, huemulite, metarossite, pascoite and rossite. The mineral occurs as transparent colourless needles, bundles of tan to brown needles and star bursts of nearly black broad blades composed of tightly intergrown needles. Crystals are elongate and striated parallel to [100], exhibiting the prismatic forms {001} and {011} and having terminations possibly composed of the forms {100} and {611}. The mineral is transparent and has a white streak, subadamantine lustre, Mohs hardness of about 2/4, brittle tenacity, irregular to splintery fracture, one perfect cleavage on {001} and possibly one or more additional cleavages parallel to [100]. Calciodelrioite is soluble in water. The calculated density is 2.451 g cm-3. It is optically biaxial (+) with α = 1.733(3), β = 1.775(3), γ = 1.825(3) (white light), 2Vmeas = 87.3(9)° and 2Vcalc = 87°. The optical orientation is X = b; Z ≈ a. No pleochroism was observed. Electron-microprobe analyses of two calciodelrioite samples and type delrioite provided the empirical formulae (Ca0.88Sr 0.07Na0.04K0.01)Σ1.00(V 1.0003)2(H2.01O)4, (Ca 0.76Sr0.21Na0.01)Σ0.98(V 1.00O3)2(H2.01O)4 and (Sr0.67Ca0.32) Σ0.99(V1.00O3)2(H 2.00O)4, respectively. Calciodelrioite is monoclinic, I2/a, with unit-cell parameters a = 14.6389(10), b = 6.9591(4), c = 17.052(2) Å, β = 102.568(9)°, V= 1695.5(3) Å3 and Z = 8. The seven strongest lines in the X-ray powder diffraction pattern [listed as dobs Å(I)(hkl)] are as follows: 6.450(100)(011); 4.350(16)(013); 3.489(18)(020); 3.215(17)(022); 3.027(50)(multiple); 2.560(28)(415,413); 1.786(18)(028). In the structure of calciodelrioite (refined to R1 = 3.14% for 1216 Fo > 4σF), V 5+O5 polyhedra link by sharing edges to form a zigzag divanadate [VO3] chain along a, similar to that in the structure of rossite. The chains are linked via bonds to Ca atoms, which also bond to H 2O groups, yielding CaO3(H2O)6 polyhedra. The Ca polyhedra form a chain along b. Each of the two symmetrically independent VO5 polyhedra has two short vanadyl bonds and three long equatorial bonds. Calciodelrioite and delrioite are isostructural and are the endmembers of the series Ca(VO3)2(H2O) 4-Sr(VO3)2(H2O)4. Calciodelrioite is dimorphous with rossite, which has a similar structure; however, the smaller 8-coordinate Ca site in rossite does not accommodate Sr. © 2012 The Mineralogical Society.

Kampf A.R.,Natural History Museum of Los Angeles County | Plasil J.,ASCR Institute of Physics Prague | Kasatkin A.V.,V O Almazjuvelirexport | Marty J.,5199 East Silver Oak Road
Mineralogical Magazine | Year: 2014

The new mineral belakovskiite (IMA2013-075), Na7(UO 2)(SO4)4(SO3OH)(H2O) 3, was found in the Blue Lizard mine, Red Canyon, White Canyon district, San Juan County, Utah, USA, where it occurs as a secondary alteration phase in association with blödite, ferrinatrite, kröhnkite, meisserite and metavoltine. Crystals of belakovskiite are very pale yellowish-green hair-like fibres up to 2 mm long and usually no more than a few mm in diameter. The fibres are elongated on [100] and slightly flattened on {021}. Crystals are transparent with a vitreous lustre. The mineral has a white streak and a probable Mohs hardness of ∼2. Fibres are flexible and elastic, with brittle failure and irregular fracture. No cleavage was observed. The mineral is readily soluble in cold H2O. The calculated density is 2.953 g cm -3. Optically, belakovskiite is biaxial (+) with α=1.500(1), β=1.511(1) and γ=1.523(1) (measured in white light). The measured 2V is 87.1(6)° and the calculated 2V is 88°. The mineral is non-pleochroic. The partially determined optical orientation is X ≈ a. Electron-microprobe analysis provided Na2O 21.67, UO3 30.48, SO3 40.86, H2O 6.45 (structure), total 99.46 wt.% yielding the empirical formula Na6.83(U1.04O2)(SO4) 4(S0.99O3OH)(H2O)3 based on 25 O a.p.f.u. Belakovskiite is triclinic, P1̄, with a=5.4581(3), b=11.3288(6), c=18.4163(13) Å, α=104.786(7)°, β=90.092(6)°, γ=96.767(7)°, V=1092.76(11) Å 3 and Z=2. The eight strongest X-ray powder diffraction lines are [dobs Å (I)(hkl)]: 8.96(35)(002), 8.46(29)(011), 5.19(100)(1̄01,101,1̄10), 4.66(58)(013,1̄02,1̄1̄0,110), 3.568(37)(120,023,005,03̄3), 3.057(59)(01̄6,11̄5,1̄31), 2.930(27)(multiple) and 1.8320(29)(multiple). The structure, refined to R 1=5.39% for 3163 Fo > 4σF reflections, contains [(UO2)(SO4)4(H2O)]6- polyhedral clusters connected via an extensive network of Na-O bonds and H bonds involving eight Na sites, three other H2O sites and an SO 3OH (hydrosulfate) group. The 3-D framework, thus defined, is unique among known uranyl sulfate structures. The mineral is named for Dmitry Ilych Belakovskiy, a prominent Russian mineralogist and Curator of the Fersman Mineralogical Museum. © 2014 The Mineralogical Society.

Chukanov N.V.,RAS Institute of Problems of Chemical Physics | Britvin S.N.,Saint Petersburg State University | Mohn G.,J. Wittemannstrasse 5 | Pekov I.V.,Moscow State University | And 4 more authors.
Mineralogical Magazine | Year: 2015

The new mineral shilovite, the first natural tetrammine copper complex, was found in a guano deposit located on the Pabellón de Pica Mountain, near Chanabaya, Iquique Province, Tarapacá Region, Chile. It is associated with halite, ammineite, atacamite (a product of ammineite alteration) and thénardite. The gabbro host rock consists of amphibole, plagioclase and minor clinochlore, and contains accessory chalcopyrite. The latter is considered the source of Cu for shilovite. The new mineral occurs as deep violet blue, imperfect, thick tabular to equant crystals up to 0.15 mm in size included in massive halite. The mineral is sectile. Its Mohs hardness is 2. Dcalc is 1.92 g cm-3. The infrared spectrum shows the presence of NH3 molecules and NO3 anions. Shilovite is optically biaxial (+), α = 1.527(2), β = 1.545(5), γ = 1.610(2). The chemical composition (electron-microprobe data, H calculated from ideal formula, wt.%) is Cu 26.04, Fe 0.31, N 30.8, O 35.95, H 4.74, total 100.69. The empirical formula is H12.56(Cu1.09Fe0.01)N5.87O6.00. The idealized formula is Cu(NH3)4(NO3)2. The crystal structure was solved and refined to R = 0.029 based upon 2705 unique reflections having F > 4σ(F). Shilovite is orthorhombic, space group Pnn2, a = 23.6585(9), b = 10.8238(4), c = 6.9054(3) Å, V = 1768.3(1) Å3, Z = 8. The strongest reflections of the powder X-ray diffraction pattern [d, Å (I,%) (hkl)] are: 5.931 (41) (400), 5.841 (100) (011), 5.208 (47) (410), 4.162 (88) (411), 4.005 (62) (420), 3.462 (50) (002), 3.207 (32) (031), 2.811 (40) (412). © 2015 Mineralogical Society.

Plasil J.,ASCR Institute of Physics Prague | Sejkora J.,National Museum | Skoda R.,Masaryk University | Novak M.,Masaryk University | And 5 more authors.
Mineralogical Magazine | Year: 2014

Hlousekite, (Ni,Co)Cu4(AsO4)2(AsO3OH)2(H2O)9, is a new supergene arsenate mineral from the Geister vein (Rovnost mine), Jáchymov (St Joachimsthal), Western Bohemia, Czech Republic. It was found along with veselovskyite, pradetite, lavendulan, arsenolite, babanekite and gypsum on the surface of strongly altered ore fragments containing dominant tennantite and chalcopyrite. Hlousekite forms thin, lath-like crystals, locally elongated reaching up to 3 mm across. It is transparent, has a pale green colour with vitreous lustre, has a greyish-white streak and it is very brittle with an uneven fracture. It does not fluoresce under shortwave or longwave ultraviolet radiation. Cleavage on {010} is perfect; the Mohs hardness is 2-3. The calculated density is 3.295 g cm-3. Hlousekite is optically biaxial with α′ = 1.653(2) and γ′ = 1.73. The estimated optical orientation is γ′ vs. elongation (c) = 14(1)°. In larger grains it is weakly to moderately pleochroic (α = colourless, γ = pale green to green). Hloušekite is triclinic, space group P1¯, a = 6.4010(6), b = 8.0041(6), c = 10.3969(14) å, α = 85.824(8), b = 79.873(9), γ = 84.655(7)° and V = 521.23(10) å3, with Z = 1, a:b:c = 0.800:1:1.299. The eight strongest lines in the powder X-ray diffraction (XRD) pattern [d in å (I)(hkl)] are 10.211(100)(001), 7.974(9)(010), 3.984(6)(020), 3.656(5)(11¯2), 3.631(5)(02¯1), 3.241(5)(022), 3.145(5)(200) and 3.006(5)(210). Chemical analysis by electron microprobe yielded MgO 0.20, FeO 0.10, NiO 5.79, CoO 1.80, CuO 29.53, ZnO 0.66, Al2O3 0.14, P2O5 0.11, As2O5 45.01, H2O 17.71 (calc.), fora total of 101.05 wt.%. The resulting empirical formula, calculated by stoichiometry (9H2O + 2OH), obtained from the crystal structure, is (Ni0.79Co0.25)Σ1.04(Cu3.78Zn0.08Mg0.05Al0.03Fe0.01)Σ3.95 (AsO4)1.98(PO4)0.02(AsO3OH)2.00(H2O)9.00. The ideal endmember formula, NiCu4(AsO4)2(AsO3OH)2(H2O)900, requires NiO 7.23, CuO 30.81, As2O5 44.51, H2O 17.45, total 100.00 wt.%. The crystal structure of hloušekite was solved by charge flipping from single-crystal XRD data and refined to R1 = 0.0599 for 1441 reflections with [Iobs > 3σ(I)]. Hlousekite is a new member of the lindackerite group (also including lindackerite, pradetite and veselovskýite) of the lindackerite supergroup. The ondrušite group of the lindackerite supergroup includes ondrušite, chudobaite, geigerite and klajite. The establishment of these two groups reflects the difference between the crystal structures of their members, mainly in the coordination environment of the Me cations. © 2014 The Mineralogical Society.

Kampf A.R.,Natural History Museum of Los Angeles County | Mills S.J.,Khan Research Laboratories | Nestola F.,University of Padua | Ciriotti M.E.,Associazione Micromineralogica Italiana | Kasaasaasatkin A.V.,V O Almazjuvelirexport
American Mineralogist | Year: 2013

Saltonseaite, K3NaMn2+Cl6, is a new mineral from the Salton Sea, Imperial County, California, U.S.A., which formed as the result of the evaporation of geothermal (hydrothermal) brines enriched in K, Na, Mn, and Cl. It occurs as lozenge-shaped and bladed crystals to about 10 cm that are composites of parallel-grown {012} rhombohedra. It is associated with large, well-formed crystals of sylvite and halite. Crystals are transparent and colorless, but appear light orange due to inclusions of akaganéite. The streak is white and the luster is vitreous to oily, the latter being due to deliquescence. The Mohs hardness is about 21/2, the tenacity is brittle, the fracture is irregular, and crystals exhibit one very good cleavage on {110}. The mineral has an astringent taste and is markedly hygroscopic. The measured and calculated densities are 2.26(1) and 2.297 g/cm3, respectively. Saltonseaite is soluble in water at room temperature and crystallizes from solution above 52 °C. Optically, saltonseaite is uniaxial positive, with ω = 1.577(1) and ε = 1.578(1) (white light) and is non-pleochroic. Energy-dispersive spectroscopic analyses (average of 5) provided: K 28.79, Na 5.35, Mn 13.48, Fe 0.24, Cl 52.19, total 100.05 wt%. The empirical formula (based on 6 Cl atoms) is: K3.00Na0.95Mn 1.002+Fe0.022+Cl6. Saltonseaite is trigonal, R3̄c, with cell parameters a = 12.0966(5), c = 13.9555(10) Å, V = 1768.48(16) Å3, and Z = 6. The nine strongest lines in the X-ray powder diffraction pattern are [dobs in Å(I)(hkl)]: 5.83(61)(012); 3.498(25)(300); 2.851(68)(131); 2.689(32)(312); 2.625(62)(214); 2.542(100)(223); 1.983(32)(324); 1.749(20)(600), and 1.384(22)(multiple). The structure of saltonseaite (R1 = 1.08% for 558 Fo > 4σF) contains face-sharing chains of alternating Mn2+Cl6 octahedra and NaCl6 polyhedra along c. The chains are joined via bonds to eight-coordinated K atoms. Saltonseaite is isostructural with rinneite, K3NaFe2+Cl6, and very similar in structure with chlormanganokalite, K4Mn 2+Cl6. Existing chemical analyses for saltonseaite and rinneite fail to confirm a solid-solution series between them; experimental studies are needed.

Kampf A.R.,Natural History Museum of Los Angeles County | Kasatkin A.V.,V O Almazjuvelirexport | Cejka J.,National Museum | Marty J.,5199 E. Silver Oak Rd.
Journal of Geosciences (Japan) | Year: 2015

Plášilite (IMA 2014-021), Na(UO2)(SO4)(OH)·2H2O, is a new uranyl sulfate mineral from the Blue Lizard mine, San Juan County, Utah, USA. The new mineral occurs in and on sandstone matrix in close association with atacamite, blödite, brochantite, calcite, chalcanthite, dickite, gerhardtite, gypsum, hexahydrite, johannite, manganoblödite, natrozippeite and tamarugite. It is a low-temperature, secondary mineral formed by the post-mining weathering of uraninite. Plášilite is monoclinic, with the space group P21/c, and unit cell parameters a = 8.7122(6), b = 13.8368(4), c = 7.0465(2) Å, β = 112.126(8)°, V = 786.89(7) Å3 and Z = 4. Crystals are long, thin blades, elongated on [001] and flattened on {100}; rarely occur as prisms, also elongated on [001]. Crystals exhibit the forms {100}, {010} and {011}, and are commonly twinned on {100}. Plášilite is greenish yellow, has a white streak and fluoresces bluish white under both long-wave and short-wave UV. It is transparent with vitreous luster. The mineral has a Mohs hardness probably between 2 and 3, brittle tenacity, even fracture and two perfect cleavages, {010} and {001}. The calculated density based on the empirical formula is 3.726 g/cm3. The mineral is optically biaxial (+), with α = 1.556(1), β = 1.581(1) and γ = 1.608(1) (measured with white light). The measured 2V is 88(1)° and the calculated 2V is 89°. Dispersion is moderate, r < v. The mineral is pleochroic with X = nearly colourless, Y = very pale yellow, Z = pale yellow; X < Y < Z. The optical orientation is X = b, Y ∧ c = 4° in obtuse β. The empirical formula of plášilite is Na0.94(UO2)(S1.01O4)(OH)(H2O)2 (based on 9 O apfu). Prominent features in the Raman spectrum include the symmetric stretching vibrations of the uranyl (UO2 2+) group and sulfate tetrahedra and the O-H stretching and bending vibrations of the H2O molecules. The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]: 6.90(100)(020), 5.85(99)(011,111), 4.024(57)(200,130), 3.492(82) (102,220,040), 3.136(40)(122), 2.690(25)(141,102,241,032), 2.618(34)(240,150,302), 1.9212(30)(mult.). The crystal structure of plášilite (R1 = 0.019 for 1603 reflections with Fobs > 4σ;F) contains uranyl sulfate sheets of composition [(UO2)2(SO4)2(OH)2]2- parallel to (010). Between the sheets and linking them to one another are chains of edge-sharing NaO2(H2O)4 octahedra parallel to [001]. The uranyl sulfate sheet is based on the phosphuranylite anion topology. The sheets in plášilite and deliensite are geometrical isomers.

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