Crystal structure of bassetite and saléeite: new insight into autunite-group minerals

Abstract

The crystal structures of two autunite-group minerals have been solved recently. The crystal structure of bassetite, Fe 2+ [(UO 2 )(PO 4 )] 2 (H 2 O) 10 , from the type locality in Cornwall, United Kingdom (Basset Mines) was solved for the first time. Bassetite is monoclinic, space group P2 1 /n, a = 6.961(1), b = 20.039(2), c = 6.974(1) A ˚and b = 90.46(1) . The crystal structure of sale ´eite, Mg[(UO 2 )(PO 4 )] 2 (H 2 O) 10 , from Shinkolobwe, Democratic Republic of Congo, was also solved. Sale ´eite is monoclinic, space group P2 1 /n, a = 6.951(1), b = 19.942(1), c = 6.967(1) A ˚and b = 90.58(1) . The crystal structure investigation of bassetite (R 1 = 0.0658 for 1879 observed reflections with |F o | ! 4s F ) and sale ´eite (R 1 = 0.0307 for 1990 observed reflections with |F o | ! 4s F ) confirms that both minerals are topologically identical and that bassetite contains ten water molecules per formula unit. Their structure contains autunite-type sheets, [(UO 2 )(PO 4 )] -, consisting of corner-sharing UO 6 square bipyramids and PO 4 tetrahedra. Iron and magnesium are surrounded by water molecules to form Fe(H 2 O) 6 or Mg(H 2 O) 6 octahedra located in interlayer, between the autunite-type sheets. Two isolated independent water molecules are also located in interlayer. Energy-dispersive X-ray spectroscopy analysis confirmed the chemical composition obtained from structure refinement. These new data prompt a re-assessment of minerals of the autunite and meta-autunite groups.

Detection and identification of solids, surfaces, and solutions of uranium using vibrational spectroscopy

“…For instance, Mg(II) cations interact more with interstitial water molecules present in the interlayer region of saleeite than with uranyl unit because the distances between the uranyl oxo and the Mg cation is 4.12 and 4.14 Å (Fig. 4b) [111]. The large interatomic distance suggests no signifi-cant interaction with the uranyl bond.…”

Chelating Effect of Siderophore Desferrioxamine-B on Uranyl Biomineralization Mediated by Shewanella putrefaciens

“…putrefaciens (Figure d 5 ,e, violet line). Conversely, the low concentration of Fe 3+ ion facilitates recurrence of the mineral crystal bassetite [Fe­(UO 2 ) 2 (PO 4 ) 2 ·8­(H 2 O)] (Figure d 4 ,e, blue line). The conclusions are consistent with the peak area of UO 2 2+ measured by using FTIR, as shown in the SI, Section 8.…”

“…However, high concentrations of Fe 3+ ion and few UO 2 2+ complexed with DFO form larger flocculent colloids, which are independent of the surface of S. putrefaciens (Figure 4d 5 ,e, violet line). Conversely, the low concentration of Fe 3+ ion facilitates recurrence of the mineral crystal bassetite [Fe- 73 (Figure 4d 4 ,e, blue line). The conclusions are consistent with the peak area of UO 2 2+ measured by using FTIR, as shown in the SI, Section 8.…”

Locating hydrogen positions in the autunite mineral metatorbernite [Cu(UO2)2(PO4)2·8H2O]: a combined approach using neutron powder diffraction and computational modelling

“…Future work should aim to use this combined approach to investigate other hydrated (trans)uranium phases for which hydrogen bonding is integral to stability. This could include sale ´eite, a magnesium autunite [Mg(UO 2 ) 2 (PO 4 ) 2 Á10H 2 O] that immobilizes uranium in natural deposits in Koongarra, Australia (Murakami et al, 1997(Murakami et al, , 2005, but for which the proposed hydrogen-bond networks are not in good agreement (Yakubovich et al, 2008;Dal Bo et al, 2016); and uranyl peroxide/hydroxide cage clusters, which show exciting promise for the separation and recycling of nuclear fuel, but for which the arrangement of hydrogen atoms and interstitial H 2 O groups has not yet been well established (Burns & Nyman, 2018).…”