The crystal structure of christelite Zn₃Cu₂(SO₄)₂(OH)₆ · 4 H₂O

Abstract

Abstract The crystal structure of christelite Zn 3 Cu 2 · (SO 4 ) 2 (OH) 6 · 4 H 2 O (space group P [unk]; lattice parameters a = 5.4143(8) Å, b = 6.336(1) Å, c = 10.470(3) Å, α = 94.32(3)°, β = 90.06(2)°, γ = 90.27(2)°) was solved using direct methods and difference Fourier-syntheses. The structure was refined to a final R ( F )-value of 0.033. The structure contains distorted [(Zn, Cu)O 6 ] octahedra which are connected as to form sheets of composition ∞ 2 [(Cu,Zn) 2 (OH) 3 O] − . These sheets are similar to those observed in the mineral ktenasite. In both structures sulphate groups are attached to the sheets of octahedra through common vertices. In christelite the tetrahedral [SO 4 ] groups are linked to isolated [Zn(H 2 O) 4 O 2 ] octahedra thus forming a three-dimensional structure, whereas in the structure of ktenasite the [SO 4 ] tetrahedra are bonded to isolated [Zn(H 2 O) 6 ] by a system of hydrogen bonds. The relationship of christelite with other minerals is pointed out and discussed.