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The processing of Cu, Co and Zn at El Boleo mine (Mexico) involves two stage (oxidation-reduction) leaching to extract Cu, Zn, Co and Mn into solution. After Cu recovery a solvent extraction circuit was used to extract both Zn and Co rejecting Mn into the tailing. Zinc is further recovered as Zn sulphate via crystallisation whereas Co is currently recovered via electrolysis to produce Co buttons at El Boleo mine. Alternative routes were tested to recover Co using hydrazine reduction and Mn cementation. At optimized conditions of hydrazine/Co molar ratio of 0.5:1, 70 °C, 7 M NaOH, over 98% Co could be recovered as 99.8% pure Co metal powder, which could be subsequently briquetted to buttons for easier handling. Cementing Co powder using Mn at various Mn/Co ratios show losses of Mn and passivation causing low Co recovery. At > 30% excess, > 95% of Co is recovered as 93% pure Co powder. During processing Zn, Fe, Mn impurities were removed as sulphide, which also caused 10% of the available Co to co-precipitate as Co sulphide containing 13.5% ZnS. Roasting of this material at > 1300 °C produced > 98% grade CoO-Co 3 O 4 , which can be recycled to the leaching stage. [ABSTRACT FROM AUTHOR]