Observation of the oxidation of galena using Raman spectroscopy

Oxidation of galena (PbS) to oxysulfates, (PbO . PbSO4, 3PbO . PbSO4 and 4P bO . PbSO4) has been observed using Raman spectroscopy. Peaks associated wi th the oxidation products have been assigned. The reaction appears to be a high temperature oxidation induced by the high laser (similar to 25 mW at 5 14.5 nm) power density at freshly cleaved galena surfaces. Damage to the ga lena surface was observed visually under the microscope. Moderate laser pow ers (similar to 5 mW at 514.5 nm) did not result in any damage. No Raman ba nds were observed or expected for freshly cleaved galena because it has the rock salt structure. Laser-induced production of these oxysulfates is dram atically different from high temperature methods previously employed. This procedure will permit easy identification of galena in complex mineral ore samples. Spontaneous air oxidation of freshly cleaved galena to oxides or p olysulfides was not detected. (C) 2000 Elsevier Science B.V. All rights res erved.