This dissertation deals with a critical appraisal of recent literature on ore reserve estimation (1966-1977) and it will treat with papers and publications within each different method (Classical Methods, Statistical Methods and Geostatistical Methods) in chronological order. Finally it should that much of the done by the authors of the Paper review is based on theory developed by only a few authors. These authors are: Carl F. Gauss, Pearson, Fisher, Sichel, Krige, Scott Hazen, Matheron, Agterberg and De Wijs. The works of these author can be found in most of the standart statistical texts and papers, the titles of the more frequently referred to are given in the bibliography.

It does not intend to demostrate new results, in the theory of ore reserve estimation, but does wish to resume and make a critical appraisal of all old methods and new methods by showing all the information which can be obtained by rather elementary techniques on papers and publications. The aim of these papers is to present basic concepts of a relatively new mathematical theory which is readily applicable to ore valuation problems.

The need for accurate ore reserve estimates has been important in the past but, with the growing shortages of natural resources, the spiralling demand for minerals, and the increasingly large investments required to open new mines today, this need becomes almost critical. Yet many of the ore reserves methods used by some authors lack a scientific foundation.

The need of improved ore valuation techniques is quite recognisedthroughout the mining industry probably because of the order of errors committed in the evaluation of ore blocks and/or working stope faces and the overall effect of such as errors on the mine profits are appreciated. Considerable progress has been made since 1952 with the weighted moving average technique for ore reserve determination.

During the last several decades the accuracy of computing reserves has gradually improved. This was made possible by outstanding advances in the field of econimic geology; increased specialisation; improvements in exploration; sampling; mining and valuation; better field information; use of statistical analysis; and more efficient management.

In general, selecting a method for reserve computation depends on the geology of the mineral deposit, exploration method, availability and reliability of factual data, purpose of computations and required degree of accuracy. The nature of the various methods should be carefully considered.

Statistical and geostatistical models in geology are fast becoming common and there is a clear evidence of a growing need for formalising geological data. In the earth science this need is more acute in the study of ore deposits, obviously because of important economic implications. The complex multivariate problems involved are best solved by electronic data processing, when large volumes of numerical data need to be processed.

The literature on the application of statistics to ore reserve calculation was recognised and divided into sections or schools for different authors according to geographical basic, it also reflected the different approaches to statistical application. There were three broad groupings:

A - The South African School, dominated by the Authors Sichel and Kridge.

B - The North American School, with Matheron and Agterberg as the most notables.

C - The French and Canadian School, with Matheron and Agterberg as the most notables.

For the present dissertation the literature was divided into three groups according to the different methods of calculating ore reserves:

A - Classical Methods.

B - Statistical Methods.

C - Geostatistical Methods.

Authors in each of these groups have generally been mining engineers or geologist or at least people with formal qualifications in statistics. The result of sampling and ore reserve estimation research by Sichel, Krige, De Wijs, Agterberg and so on, and more recently by Matheron have made significant contributions to the current art of ore reserve estimation.

The general philosophy on which engeneers and geologist by nature tend to be pragmatic types in estimating the quantitative appraisal of regional mineral potencial and getting satisfactory answers is not based in mathematical theory. This approach is a new topic of research in economic geology. But not always do these empirical techniques yield the correct answer. It was this fact that led some authors to experiment with statistical and geostatistical techniques to provide more satisfactory answers. Although statistics have been used by engeneers and geologists for many years only recently has the subject received the attention needed and deserved.

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¹ London University, Imperial College, Royal School of Mines, Octubre 1977.