A metallurgical evaluation of the Mi Vida prospect: A mixed copper sulfide-carbonate ore body, Sells, Pima County, Arizona

A copper-prospect in south-central Arizona has been evaluated on a metallurgical basis. Primary chalcocite and secondary covellite, plus the copper oxides malachite and brochantite, constitute the economic mineralization. The deposit outcrops as a steeply dipping (70°SW), intensely brecciated, copper-bearing quartz vein with discontinuous lenticular ore shoots. Acid leaching techniques alone and in conjunction with froth flotation utilizing four copper oxide specific collectors were used to evaluate the amenability of this ore to processing. Direct acid leaching was examined and found to be ineffective. Removal of the chalcocite by froth flotation with xanthate was easy and gave better results to subsequent leaching steps; the oxide phases of the ore proved more difficult to concentrate. Copper oxide recovery was investigated using the following collectors and methods: 1) fatty acids (carboxylic acids); 2) potassium octyl hydroxamate; 3) monoalky ldithiocarbamates ; 4) sulphidation with NaHS plus xanthate collector; and 5) froth flotation plus acid leaching of tails. The carboxylic acid collectors produced extremely low recoveries. Potassium octyl hydroxamate and the monoalkyldithiocarbamate collectors gave recoveries of 93 pet or better. The hydroxamate is too expensive to utilize as a collector, while the carbamate is cheaper but not available in commercial quantities. Sulphidation with NaHS proved effective but hard to control without instrumentation; recoveries were typically in the 85 pet to 93 pet range. Froth flotation followed by acid leaching yielded recoveries up to 97 pet with moderate cost. A proposed flowsheet would call for chalcocite flotation with potassium amyl xanthate (KAX) at a grind of -150 µm (-100 mesh) followed by sulphidation with NaHS and copper oxide flotation with KAX. Flotation tailings would then be given an agitation acid leach to recover the remaining copper values --Abstract, pages ii-iii