The advantages of X-ray absorption spectroscopy have been utilized to assess the Cu and Zn ordering in aurichalcite, (Cu5−xZnx)(OH)6(CO3)2. We have examined one hydrozincite sample and three aurichalcite samples in which the Cu:Zn ratios are in the range 1:3 to 2:3. Copper 2p XAS confirms that there is no monovalent copper in aurichalcite and that in each sample the copper might be distributed across more than one metal site. EXAFS, at the Cu and Zn K-edges, shows that the copper atoms preferentially enter the Jahn-Teller elongated, octahedral (M2) and trigonal bipyramidal (M4) sites, with the zinc atoms entering the more regular octahedral (M1) and tetrahedral (M3) site. Substantial solid solution towards the zinc rich region is facilitated by the substitution of copper by zinc on the M2 and M4 sites. This information, not easily obtained by X-ray diffraction, substantially enhances the understanding of the structure of aurichalcite.

Brianyoungite, which is chemically and structurally related to hydrozincite, occurs as white rosettes (<100 μm) with gypsum on rubbly limestone within the oxidised zone at Brownley Hill Mine, Nenthead, Cumbria. The mineral contains (wt.%) 71.47 ZnO, 9.90 CO2, 6.62 SO3 and 10.70 H2O+. Based on 29 oxygen atoms, the empirical formula is Zn11.73[(CO3)3.00,(SO4)1.10]4.10(OH)15.88 or ideally Zn3(CO3,SO4)(OH)4. Brianyoungite is either orthorhombic or monoclinic with β very close to 90° Cell parameters determined by electron diffraction and refined from X-ray powder diffraction data are a = 15.724, b = 6.256 and c = 5.427 Å. Density is > 3.93, < 4.09 g/cm3 (meas.) and 4.11 g/cm3 (calc.); Z = 4. Thermogravimetric analysis, IR and XRD powder data (23 lines) are presented.