One of us, J.A., is very grateful to CONCYTEC for a scholarship financing doctoral studies. A.T. is also very grateful to Universidad Nacional de Ingeniería and MINEDU Perú for special grants as a researcher professor. We are very thankful to H. Huanca and C. Luyo for achieving our X-ray diffractograms.

Understanding the changes of a mineral during ore processing is of capital importance for the development of strategies aimed at increasing the efficiency of metal extraction. This task is often difficult due to the variability of the ore in terms of composition, mineralogy and texture. In particular, surface processes such as metal re-adsorption (preg-robbing) on specific minerals are difficult to evaluate, even though they may be of importance as the re-adsorbed material can be blocking the valuable mineral and negatively affect the extraction process. Here, we show a simple yet powerful approach, through which surface processes in individual minerals are identified by combining polarization microscopy (MP) and X-ray photoelectron spectroscopy (XPS). Taking as an example a silver-containing polymetallic sulfide ore from the Peruvian central Andes (pyrite-based with small amounts of gal...

Leaching of polymetallic sulfides is often challenging due to the complexity of these systems. The main issues are related to the formation of surface by-products or to the presence of different metals that require a greater consumption of chemicals compared to that needed to extract the target metal during leaching. This latter case is followed in the present work using X-ray photoelectron spectroscopy (XPS) during the leaching of a silver-containing polymetallic (Mn-Fe-Pb) sulfide under three different cyanidation procedures: (1) conventional leaching, (2) ultrasound-assisted leaching, and (3) leaching of a sample pretreated in alkaline media. In all cases, leaching results in the build-up of Pb compounds (oxides/hydroxides) on the surface of the minerals, suggesting a mechanism in which Pb is first leached by hydroxide and cyanide and later is re-adsorbed as an external layer on the m...