Projection of Data

Abstract

Abstract The Samples on which all ore reserve estimates are based are but a minute portion of the total deposit. Closely spaced drilling of the small Copper Flat porphyry copper deposit in New Mexico produced about 200 tons of core, yielding 3 tons of assay pulps (only a small portion of which was actually analyzed) with which to define 60 million tons of ore and roughly 150 million tons of waste (Dunn, 1992). The values obtained from these tiny portions of the deposit must necessarily be projected into the vast unknown volume surrounding the sample points. In most discussions of reserve estimation, the various methods of projecting sample data focus on projections of grade or tenor. A proper reserve estimate, however, requires the estimation of numerous other parameters necessary to define the true worth of the deposit. Such parameters might include specific gravity, vein thickness, ore type, metallurgical recovery, moisture content, rock hardness or grindability, proportion of deleterious components, and geotechnical parameters (e.g., rock quality designation). Obviously, any or all of these parameters may vary from place to place within the deposit, but with few exceptions, (e.g., vein thickness, mineralogy or ore type, and sometimes specific gravity), they are more often taken as overall averages rather than adequately evaluated in even the most elegant reserve estimates and reports. In addition to the characteristics of the ore itself, it is sometimes necessary to estimate various values within the waste rock or material that must be left in place for environmental or