Lussierite, a new sodium uranyl sulfate mineral with bidentate UO 7 –SO 4 linkage from the Blue Lizard mine, San Juan County, Utah, USA

Abstract

The new mineral lussierite (IMA2018-101), Na 10 [(UO 2 )(SO 4 ) 4 ](SO 4 ) 2 (H 2 O) 3 , was found in the Blue Lizard mine, San Juan County, Utah, USA, where it occurs as pale green–yellow prisms or blades in a secondary assemblage with belakovskiite, ferrinatrite, halite, ivsite, metavoltine and thénardite. The streak is white and the fluorescence is bright cyan under 365 nm ultraviolet light. Crystals are transparent with vitreous lustre. The tenacity is brittle, the Mohs hardness is 2½, the fracture is irregular and no cleavage was observed. The mineral is easily soluble in H 2 O and has a measured density of 2.87(2) g cm –3 . Lussierite is optically biaxial (+), with α = 1.493(1), β = 1.505(1) and γ = 1.518(1) (white light); 2V meas. = 88(1)°; dispersion is r > v , moderate; pleochroism: X = colourless, Y and Z = green yellow ( X 2σ I ) contains a [(UO 2 )(SO 4 ) 4 ] 6– uranyl sulfate cluster in which one SO 4 tetrahedron shares an edge (bidentate linkage) with the UO 7 pentagonal bipyramid. The uranyl sulfate clusters occur in layers and are linked through a complex network of bonds involving Na + cations, isolated SO 4 tetrahedra and isolated H 2 O groups.