This will depend on the specific resource modeling case.įurther justification for compositing is that small scale assays may be highly variable, which can be mitigated by compositing. The blocks may be as small as 5 × 5 × 5 m (for smaller, selective deposits), equivalent perhaps to 350 metric tons, and up to 25 × 25 × 15 m or larger blocks for massive depos- its, equivalent to almost 25,000 tons considering an in-situ bulk density of 2.65 t/m3. This is because the sample is (a) usually composited, and (b) multiple composites are used to estimate blocks. Although the two sample weights are quite different, the difference and its impact is negligible. The corresponding HQ-size DDH, for the same 1 m length, will represent close to 28 kg.
For a 1 m interval, a typical RC drill hole sample will represent close to 50 kg, considering that a 5.25-inch diameter hole is drilled. In practice, slight differences in support size will have little effect on the final resource estimate.Ĭonsider an operation that has both reverse circulation (RC) and diamond drill holes (DDH) in its resource data- base. There will also be partial composites at the end of drill holes or at hard geologic contacts.
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There are geostatistical models that can provide for mixtures of support sizes in the original data, but estimation software almost always assumes the data are of constant support.ĭrill holes of different diameters are commonly used in the same deposit. Regular length or bench composites are most common in resource estimation. Each of these types of composites are produced for different purposes and in different situations.