this neutralizing action in this stage accelerates the beginning of the extraction of the target metals when there is no addition of acid in this stage and agglomeration is only carried out with water either with or without binder agents a delay is observed in the extraction of target metals particularly nickel and cobalt although no significant impact is observed on the total leaching cycle normally magnesium iron aluminium and calcium are the major acid consuming species after agglomeration ii the ore is stacked iii forming heaps whose final heights range from about 2 m to about 7 m preferably 4 meters the leaching system iv proposed is in dynamic or on off heaps counter current multi stage with the number of stages being 2 or more preferably 3 stages the system described herein follows the conceptuation as presented by foust et allii in principles of unit operations mentioned in the description of the state of the art being a leaching unit operation the two phases are comprised of the ore solute whose metal values chiefly ni and co are to be extracted and the sulfuric acid solution solvent the two phases are fed at opposite ends of a series of balanced stages and flow in directions opposite to each other with this technique higher concentrations of ni and co in the product of the liquid phase and a shorter leaching cycle as well are obtained and a smaller amount of solvent is used in comparison with the co current circuit or parallel flows the new leaching solution u2014 a sulfuric acid solution with concentration varying from about 50 g l to about 200 g l u2014 is applied to the top or upper surface of the heap of the.