The X-Ray Crystallography of Rosasite From Tsumeb, Namibia

Abstract

AbstractCrystals of green to bluish green rosasite from Tsumeb, Namibia are monoclinic, space group P21/a, with refined unit-cell parameters a = 12.873 (3), b = 9.354 (3), c = 3.156 (2) A, β = 110.36 (3)°, V = 356.3 (5) A3 and a:b:c = 1.3762:1:0.3374, with Z = 4 and Dx = 4.15 g./cm.3. Crystals are twinned by 180° rotation about a*. A fully indexed powder pattern is presented. Electron-microprobe analyses, average (wt. %): Cu 32.9, Zn 23.7; this suggests an analytical formula of (Cu1·18 Zn0·82) (CO3) (OH)2. The rosasite is optically biaxial negative, α = 1.673 (1), β = 1.796 (3), γ = 1.811 (3), 2Vx = 33 (5)° (calc. 36.4°), with X = c, Y = a* and Z = b.