The degree of fragmentation achieved at each step of any rock breakage system such as blasting, crushing and grinding has an impact on the costs of the gold process recovery and the plant design must take the appropriate conditions. With the development of new approaches to drilling and blasting, and in view of the large size of the gold operations, increasing attention is being given to the optimization of the overall fragmentation system. It is important that the supervisory personnel in both the mine and the process plant consider the overall effect of any change in practices. In this way, top management must support the concept of optimization by appreciating that a few extra cents spent at the mine has an impact on the gold recovery process and the economy of the operation.
With the trend toward larger drills, shovels and trucks, and with the advent of the explosives, the optimum fragmentation of last year might not necessarily be the best today. Sometimes, it is difficult to evaluate the effect of particular change because it is masked by other processes. In such cases, knowledge of the principles related to the fragmentation process is the best alternative to the proper direction to take respect to the degree of fragmentation. About the economy, secondary breakage costs tend to increase rapidly in very poor blasts, thus having an important effect. Drilling and blasting costs represent a relatively small portion of the total related system, especially for those gold operations having no hard rock. For this reason, the opportunities of recuperating at least a part of any increased drilling and blasting costs later is a good idea.
Optimum fragmentation for a mining alone, up to crushing, is not generally optimum for all the system. Basically, the size range of optimum fragmentation is considerable finer for small gold operations than for large operations, and for easy breaking rock than for tough breaking rock. Cost increases rapidly and apparently rather slowly as fragmentation departs from the optimum on the smaller side. In this way, it is important that management should study improved fragmentations. Also, some gold heap leaching operations do not require to crush the blasted rocks, but the maximum particle size has an impact on the gold recovery process. When Yanacocha start its operation, the one critical aspect during the first months was the blasting procedure.