Processing & Extraction of Gold & Silver from Sulphured Minerals

In this work the results obtained in the processing y extraction of gold and silver of the mineral of El Dorado-SP in this work are presented. The first stage consisted of collective flotation of the sulphurs, and concentrates were obtained with tenors of 10.7 g/t of silver, with recuperations of the order of 86% Au and 85% Ag. In the stage of extraction of the metals, due to the characteristics of the mineral, a previous ustullation turned out to be necessary, with the objective of obtaining a more appropriate product to the lixiviation. In these conditions, recuperations of around 93% for the gold and silver were obtained.

In the present work the results obtained through the benefits and extraction of gold and of silver contained in the sulphate mineral of El Dorado (valley of Riviera – SP) are presented. The work consisted in two stages:

- the first tried to study the viability of the concentration of sulphurates and of the existent noble minerals which are in the mineral, with a high discarding of masses and tenors of gold and silver adequate to the extractive metallurgy. In this phase, the studies consisted basically of mineralogical characterization, grinding and practices of concentration.

In the studies of mineralogical characterization performed, we identified the following minerals: quartz, arseno-pyrrite, pyrrite and escorodite. The gold was presented disseminated in the sulphurs while on the meantime, analysis performed by espectrography of emmision and electronic microsounding showed that the escorodite mineral also posses gold.

We studied, then, two alternatives for the process of concentration of the sulphurs: gravimetric concentration in vibratory table and flotation.

The tests in vibratory table did not present good results, due to the fact that the recuperations for gold and silver were not satisfactory. We decided then, for the collective flotation of all the sulphurs. In this the discarding of the mass was of the order of 63.5%. starting from a feeding with 4.5 g/t of gold and 30.0 g/t of silver with recuperation of 86% Au and 85% Ag.

The second stage showed the extraction of metals of interest (gold and silver with high recuperation).

After an intervention where the processes implied were commented, the tests and discussions of the results obtained were related. Initially, we tried to treat the concentrate directly by lixiviation with sodium cyanide. The recuperation, even in exceptional conditions of operation, were not able to go beyond 50%. This behaviour was expected, by nature of the material (arseno-pyrrite). A stage of previous ustullation became indispensable, to obtain one product more appropriate for the lixiviation. Among the conditions studied, the ideal procedure (N2-ar) showed a discarding of mass of 25%.

The material obtained was submitted to cyanidation in determined conditions, and administered recuperation around the 93%. With base of the results obtained, preliminary fluxograms were elaborated for the stages of beneficiarying and extractive metallurgy.