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Nollmotzite, Mg[U V (U VI O 2 ) 2 O 4 F 3 ]·4H 2 O, the first natural uranium oxide containing fluorine
Author(s) -
Plášil Jakub,
Kampf Anthony R.,
Škoda Radek,
Čejka Jiří
Publication year - 2018
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520618007321
Subject(s) - crystallography , octahedron , monoclinic crystal system , crystal structure , uranium , chemistry , electron microprobe , mineralogy , physics , nuclear physics
Nollmotzite (IMA2017‐100), Mg[U V (U VI O 2 ) 2 F 3 O 4 ](H 2 O) 4 , is a new uranium oxide fluoride mineral found in the Clara mine, Black Forest Mountains, Germany. Electron microprobe analysis provided the empirical formula (Mg 1.06 Cu 0.02 ) Σ1.08 [U V (U VI O 2 ) 2 O 3.85 F 3.15 ][(H 2 O) 3.69 (OH) 0.31 ] Σ4.00 based on three U and 15 O + F atoms per formula unit. Nollmotzite is monoclinic, space group Cm , with a = 7.1015 (12) Å, b = 11.7489 (17) Å, c = 8.1954 (14) Å, β = 98.087 (14)°, V = 676.98 (19) Å 3 and Z = 2. The crystal structure [twinned by reticular merohedry; refined to R = 0.0369 with GoF = 1.09 for 1527 unique observed reflections, I > 3σ( I )] is based upon [U V (U VI O 2 ) 2 F 3 O 4 ] 2– sheets of β‐U 3 O 8 topology and contains an interlayer with MgF 2 (H 2 O) 4 octahedra. Adjacent sheets are linked through F–Mg–F bonds, as well as via hydrogen bonds. The presence of fluorine and pentavalent uranium in the structure of nollmotzite has potentially important implications for the safe disposal of nuclear waste.