Mineral resources and ore reserve estimation — the AusIMM guide to good practice / Оценка минеральных ресурсов и запасов руды — путеводитель AusIMM по лучшим практикам

Risk in project evaluation involves the probability of estimates failing. There are few more risk prone businesses than mining. Burmeister (1989) reviewed 35 Australian gold operations which were initiated in the period 1984 to 1987 and found that two-thirds of them had not achieved targeted gold production in the first full year of operation. For those that did exceed target, the overriding reason was a higher than anticipated plant throughput. Only two out of the 35 achieved their projected recovered grade. Burmeister observed that the reasons for the shortfall in grade included excessive dilution, inappropriate estimation techniques, inadequate geological interpretation, unreliable assays and inadequate drilling.

Clow (1990) examined 25 advanced Canadian gold projects and found only three had lived up to expectations. He concluded that the main reason for failure was poor reserve estimation with a particular emphasis on:

1. poor data management;

2. inappropriate treatment of high-grade values;

3. lack of bulk sampling;

4. errors from application of geostatistics; and

5. inadequate assessment of dilution and mining method. <...>