Paper SS-TuP11
Identification of Surface Processes in Individual Minerals of a Complex Ore through the Analysis of Polished Sections using Polarization Microscopy and X-ray Photoelectron Spectroscopy (XPS)

Tuesday, October 23, 2018, 6:30 pm, Room Hall B

The changes at the surface level of a mineral during ore processing is of fundamental

importance for the improvement of strategies aimed at increasing the efficiency of metal

extraction. This task is often difficult due to the refractory behavior of minerals and the

deficiency of valuable metals within them. Specifically, surface processes such as metal

readsorption (preg-robbing) on specific minerals are difficult to evaluate, this process can block

or encapsulate the valuable mineral and affect negatively the extraction process. In this study,

we show a powerful approach, through which surface processes in individual minerals are

identified by combining polarization microscopy (MP) and X-ray photoelectron spectroscopy

(XPS). A silver-containing polymetallic sulfide ore from the Peruvian central Andes (pyrite-

based with small amounts of galena and covellite) is evaluated, and we track the gradual

changes in the sample during the course of leaching with cyanide. The polarization microscopy

technique identifies mineralogical species such as pyrite, galena, and covellite, while XPS

provides evidence of readsorption of lead on the surfaces of pyrite and covellite after leaching,

possibly as lead oxide or thiosulfate. The surface of pyrite does not show significant changes

after leaching process according to the microscopic result, although species of oxidized iron

are detected together with the readsorption of lead by XPS. The methodology shown here is a

tool of significant importance for understanding complex surface processes affecting various

minerals during metal extraction and highlights the importance of using surface analytical

techniques for the development of novel strategies in the mining industry.