In most of the openpit precious-metal mines in Nevada, there is no clear geological distinction between ore and waste material. The ore bodies mined in the state are highly discontinuous in terms of grade distribution. Hence, grade-control procedures are demanding. Ore polygons are defined before blasting using blasthole assays. Drilling and blasting practices have been developed that are intended to optimize grade control by minimizing forward rock movement, while creating a suitable product for load and haul operations. A study of the techniques now in use in Nevada was carried out and the results are presented. Several methods in use in Nevada would not be readily applicable in areas in which good fragmentation is more difficult to achieve.
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