X-ray powder diffraction data for botallackite

Botallackite, Cu 2 (OH) 3 Cl, from the Botallack mining area in Cornwall, United Kingdom, has been reinvestigated regarding physical, optical, chemical, and X-ray powder diffraction data. It forms emerald-green tabular crystals slightly elongated along [010] with {001} (dominant), {100}, {010}, and {011}. Botallackite is biaxial positive, 2 V =70(2)°, the optical orientation is Y ∧ c 22(2)° (in obtuse β ), Z = b . Electron-microprobe analyses gave CuO 73.26, ZnO 0.22, Cl 16.80, H 2 O (calc) 12.37, total 102.65, less O=Cl 3.79, total 98.86 wt %, corresponding to the empirical formula Cu 1.99 Zn 0.01 (OH) 2.97 Cl 1.03 (based on four anions). Unit cell parameters refined from X-ray powder diffraction data are a 5.7155(5), b 6.1255(6), c 5.6336(4) Å, β 93.090(8), V 196.95(2)Å 3 , Z =2.