Crystal structure of pseudojohannite, with a revised formula, Cu₃(OH)₂[(UO₂)₄O₄SO₄)₂](H₂O)₁₂

Abstract

The crystal structure of pseudojohannite from White Canyon, Utah, was solved by charge-flipping from single-crystal X-ray diffraction data and refined to an Robs = 0.0347, based on 2664 observed reflections. Pseudojohannite from White Canyon is triclinic, P1̄, with a = 8.6744(4), b = 8.8692(4), c = 10.0090(5) Å, α = 72.105(4)°, β = 70.544(4)°, γ = 76.035(4)°, and V = 682.61(5) ų, with Z = 1 and chemical formula Cu₃(OH)₂[(UO₂)₄O₄(SO₄)₂](H₂O)₁₂. The crystal structure of pseudojohannite is built up from sheets of zippeite topology that do not contain any OH groups; these sheets are identical to those found in zippeites containing Mg²+, Co²+, and Zn2+. The two Cu²+ sites in pseudojohannite are [5]- and [6]-coordinated by H₂O molecules and OH groups. The crystal structure of the pseudojohannite holotype specimen from Jáchymov was refined using Rietveld refinement of high-resolution powder diffraction data. Results indicate that the crystal structures of pseudojohannite from White Canyon and Jáchymov are identical.