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Leószilárdite, the first Na,Mg-containing uranyl carbonate from the Markey Mine, San Juan County, Utah, USA

Published online by Cambridge University Press:  02 January 2018

Travis A. Olds*
Affiliation:
Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
Luke R. Sadergaski
Affiliation:
Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
Jakub Plášil
Affiliation:
Institute of Physics, Academy of Sciences of the Czech Republic, v.v.i., Na Slovance 1999/2, 18221 Praha 8, Czech Republic
Anthony R. Kampf
Affiliation:
Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA
Peter C. Burns
Affiliation:
Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, USA Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
Ian M. Steele
Affiliation:
Notre Dame Integrated Imaging Facility, University of Notre Dame, Notre Dame, IN 46556, USA
Joe Marty
Affiliation:
5199 East Silver Oak Road, Salt Lake City, UT 84108, USA
Shawn M. Carlson
Affiliation:
245 Jule Lake Road, Crystal Falls, MI 49920, USA
Owen P. Mills
Affiliation:
Applied Chemical and Morphological Analysis Laboratory, Michigan Technological University, Houghton, MI 49931, USA
*
*E-mail: tolds@nd.edu

Abstract

Leószilárdite (IMA2015-128), Na6Mg(UO2)2(CO3)6·6H2O, was found in the Markey Mine, Red Canyon, White Canyon District, San Juan County, Utah, USA, in areas with abundant andersonite, natrozippeite, gypsum, anhydrite, and probable hydromagnesite along with other secondary uranium minerals bayleyite, čejkaite and johannite. The new mineral occurs as aggregates of pale yellow bladed crystals flattened on ﹛001﹜ and elongated along [010], individually reaching up to 0.2 mmlong. More commonly it occurs as pale yellow pearlescent masses to 2 mm consisting of very small plates. Leószilárdite fluoresces green under both longwave and shortwave ultraviolet light, and is translucent with a white streak, hardness of 2 (Mohs), and brittle tenacity with uneven fracture. The new mineral is readily soluble in room temperature H2O. Crystals have perfect cleavage along ﹛001﹜, and exhibit the forms ﹛110﹜,﹛001﹜,﹛100﹜,﹛101﹜ and ﹛101﹜. Optically, leószilárdite is biaxial (-), α= 1.504(1), β= 1.597(1), γ= 1.628(1) (white light); 2V (meas.) = 57(1)°, 2V (calc.) = 57.1°; dispersion r > v, slight. Pleochroism: X= colourless, Y and Z= light yellow; X<YZ The average of six wavelength dispersive spectroscopic analyses provided Na2O 14.54, MgO 3.05, UO3 47.95, CO2 22.13, H2O 9.51, total 97.18 wt.%. The empirical formula is Na5.60Mg0.90U2O28C6H12.60, based on 28 O apfu. Leószilárdite is monoclinic, C2/m, a = 11.6093(21), b = 6.7843(13), c = 15.1058(28) Å, β = 91.378(3)°, V= 1189.4(4) Å3 and Z = 2. The crystal structure (R 1 = 0.0387 for 1394 reflections with Iobs > 4σI), consists of uranyl tricarbonate anion clusters [(UO2)(CO3)3]4- held together in part by irregular chains of NaO5(H2O) polyhedra sub parallel to [010]. Individual uranyl tricarbonate clusters are also linked together by three-octahedron units consisting of two Na-centred octahedra that share the opposite faces of a Mg-centred octahedron at the centre (Na–Mg–Na), and have the composition Na2MgO12(H2O)4. The name of the new mineral honours the Hungarian-American physicist, inventor and biologist Dr. Leó Szilárd (1898–1964).

Information

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2017

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