Raman spectroscopy of basic copper(II) and some complex copper(II) sulfate minerals: Implications for hydrogen bonding

Studies of the basic Cu sulfate minerals have existed for some time (Fowles 1926; Richmond and Wolfe 1940; Ungemach 1924). Such minerals are formed under specific conditions of pH and sulfate ion concentration. The minerals in this group are dolerophanite Cu2OSO4 (Richmond and Wolfe 1940), antlerite Cu3SO4(OH)4 (Araki 1961; Finney and Araki 1963), brochantite Cu4SO4(OH)6 (Helliwell and Smith 1997), and posnjakite Cu4SO4(OH)6⋅H2O, langite Cu4SO4(OH)6⋅2H2O, and wroewolfeite Cu4SO4(OH)6⋅2H2O (Pollard et al. 1990). Antlerite is more stable under acidic conditions than is brochantite. The temperature of crystallization is significant in the synthesis of these minerals, with posnjakite formed at lower temperatures than brochantite. These minerals have been studied for various reasons: (1) as possible materials for the restoration of frescoes (Bersani et al. 2001); (2) corrosion and restoration of copper and bronze objects (Kratschmer et al. 2002; Livingston 1991; Lobnig et al. 1999; Mankowski et al. 1997; Matsuda et al. 1997; Nord et al. 1998; Bouchard-Abouchacra 2001); (3) corrosion of copper pipes containing reticulated water; (4) formation of these types of minerals in volcanic sublimations (Vergasova et al. 1988, 1984); and (5) formation of these types of minerals as leachates from slag dumps (Ruesenberg and Paulis 1996; Wappler and Tischendorf 1980). Recent work by Bouchard-Abouchacra (2001) using Raman microscopy identified brochantite and antlerite on the corroded surface of a bronze object. Bouchard-Abouchacra (2001) also was able to distinguish the minerals malachite, azurite, brochanABSTRACT