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A chemical, mineralogical and granulometric characterization of the waste tailings of Pachuca, Hidalgo, Mexico, was conducted. Characterization results indicate that these argentian wastes contain 56 g Ag ton−1 in a quartz matrix, where silver is present as metal, as argentite and as argentian-jarosite. Results on the nature of the alkaline cyanidation reaction demonstrate that it can be divided into two processes: the first process consists of a quick cyanidation of the metal silver and of argentite. A second process then takes place: the alkaline decomposition of the argentian-jarosite where the decomposition products of this ore are quickly cyanided. Therefore, this second process consists of two consecutive phases, as previously observed in other studies on synthesized argentian-jarosite-type compounds. The chemical-control and diffusive-control kinetic models were tested in order to determine which model controls the global alkaline cyanidation process. We found that once the quick cyanidation (process 1) of metal silver and argentite takes place, the experimental results corresponding to process 2 adapt to both models with a similar regression coefficient. It can be concluded that the global decomposition and cyanidation process of argentian-jarosite is controlled in a mixed manner. The experimental rate constant obtained in this study for the naturally formed jarosite was 0.007 min−1, which is very similar to that of the synthetic jarosite obtained in previous studies.

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