Processing Options For Buckhorn Sulphide Ore

The Buckhorn Mine in Nevada currently treats oxide ore using heap leach methods, but exploration has identified sulphide reserves which are refractory in nature. Preliminary testwork was conducted on the sulphide material to screen potential pre-cyanidation treatment methods. Processes evaluated included pressure oxidation, biological oxidation, nitric acid oxidation and roasting. An initial economic and process analysis of the results concluded that roasting was the only viable process, and only if the roaster off-gases were converted to soleable sulphuric acid. Further economic analysis indicated that roasting of the whole ore was more attractive than pre-concentrating by flotation, followed by roasting of the concentrate. These results were generalized to show that for high sulphur ore a roaster/acid plant combination is more attractive that either of the other options, ie. pressure leaching or bioleaching, provided the by-product acid is soleable.