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Larisaite, Na(H (sub 3) O)(UO (sub 2) ) (sub 3) (SeO (sub 3) ) (sub 2) O (sub 2) .4H (sub 2) O, a new uranyl selenite mineral from Repete Mine, San Juan County, Utah, U.S.A.

Nikita V. Chukanov, Dmitry Yu. Pushcharovsky, Marco Pasero, Stefano Merlino, Anna V. Barinova, Steffen Moeckel, Igor V. Pekov, Aleksandr E. Zadov and Viktor T. Dubinchuk
Larisaite, Na(H (sub 3) O)(UO (sub 2) ) (sub 3) (SeO (sub 3) ) (sub 2) O (sub 2) .4H (sub 2) O, a new uranyl selenite mineral from Repete Mine, San Juan County, Utah, U.S.A.
European Journal of Mineralogy (April 2004) 16 (2): 367-374


Larisaite, a new uranyl selenite with the idealized formula Na(H (sub 3) O)(UO (sub 2) ) (sub 3) (SeO (sub 3) ) (sub 2) O (sub 2) . 4H (sub 2) O, has been found in a sedimentary rock from Repete mine near Blanding, San Juan Co., Utah, U.S.A., in association with quartz, haynesite, andersonite, wolsendorfite, uranophane, gypsum, calcite and montmorillonite. The mineral is named in memory of Russian mineralogist and crystallographer Larisa Nikolaevna Belova (1923-1998) who made a significant contribution to the knowledge on the uranium minerals. Larisaite forms coarse lamellar crystals up to 1 mm and radial aggregates up to 2 mm. It is transparent or translucent, yellow, lustre vitreous, streak yellow. Fluorescence under the UV light is green (wavelengths of excitation 250 nm). Larisaite is sectile, with Mohs' hardness 1, perfect cleavage on (010) and uneven fracture across the cleavage direction. Calculated density is 4.50 g/cm (super 3) from the crystal structure refinement and 4.46 g/cm (super 3) from the empirical formula. Optically biaxial (-), alpha 1.597(2), beta 1.770(5), gamma 1.775(5); -2V nearly equal 20 degrees . Dispersion is strong, r<v. Orientation: X = b, Z coincides with the direction of elongation. Pleochroism: gamma (yellow) nearly equal beta (yellow) > alpha (light greenish-yellow). IR spectrum is given. Average values for 3 point microprobe analyses (wt.%, ranges are given in brackets) are: Na (sub 2) O 2.04 (1.82-2.32), K2O 0.69 (0.62-0.76), CaO 0.23 (0.17-0.30), UO (sub 3) 72.19 (71.77-72.64), SeO (sub 2) 18.12 (17.83-18.48); H (sub 2) O content determined by Penfield method is 7.64; total 100.91 wt.%; contents of Mg, Sr, Ba, Pb, Zn, Mn, Ni, Co, Cu, Fe, Al, Si, S, As, Cl, F are lower than detection limits i.e. < 0.02-0.05%. the empirical formula based on (SeO (sub 3) ) (sub 2) O (sub 2) is: Na (sub 0.81) K (sub 0.18) Ca (sub 0.05) (H (sub 3) O) (sub 0.73) (UO (sub 2) ) (sub 3.09) (SeO (sub 3) ) (sub 2) O (sub 2) .4.1H (sub 2) O. 1-(K (sub P) /K (sub c) ) = 0.013 ("superior"). The crystal structure has been determined (R=0.067). Larisaite is monoclinic, space group P11m; a = 6.9806(9), b = 7.646(1), c = 17.249(2) A, gamma = 90.039(4)o, V = 920.64 A (super 3) , Z = 2. The strongest lines in the powder diffraction pattern [d , A (I, %) (hkl)] are: 8.63 (43) (002), 7.67 (100) (010), 3.85 (40) (-113, 020, 113), 3.107 (77) (211), 2.874 (53) (006, -115). By the U:Se ratio, the values of unit cell parameters and the structure type, larisaite is related to haynesite, guilleminite and piretite. In common with guilleminite, uranium polyhedra and SeO (sub 3) triangles form the sheets, however the distribution of interlayer cations and H (sub 2) O molecules is different. Holotype specimen is deposited in the Geoscientific Collections of Freiberg University of Mining and Technology, Faculty of Geosciences, Geotechnics and Mining, Freiberg, Germany (the inventory number 80251).

ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 16
Serial Issue: 2
Title: Larisaite, Na(H (sub 3) O)(UO (sub 2) ) (sub 3) (SeO (sub 3) ) (sub 2) O (sub 2) .4H (sub 2) O, a new uranyl selenite mineral from Repete Mine, San Juan County, Utah, U.S.A.
Affiliation: Institute of Problems of Chemical Physics, Moscow, Russian Federation
Pages: 367-374
Published: 200404
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 15
Accession Number: 2004-042039
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
N37°00'00" - N38°30'00", W111°13'00" - W109°02'60"
Secondary Affiliation: Moscow State University, RUS, Russian FederationUniversita di Pisa, ITA, ItalyAlpha-geophysik in Sachsen, DEU, Federal Republic of GermanyNPO Regenerator, RUS, Russian FederationAll-Russian Scientific-Research Institute of Mineral Resources, RUS, Russian Federation
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200412
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