Ordinary kriging and non-linear geostatistical estimators are now well accepted methods in mining grade control and mine resource estimation. Kriging is also a necessary step in the most commonly used methods of conditional simulation used in the mining industry. In both kriging and conditional simulation, the search volume or ‘kriging neighbourhood’ is defined by the user. The definition of this search can have a very significant impact on the outcome of the kriging estimate or the quality of the conditioning of a simulation.

Classification of mineral resource estimates is one of the most important responsibilities of the Competent Person. In recent years, classification decisions have been driven more by the detailed block-by-block attributes generated by the now widely appliedgeostatistical estimation methods, and less by a general geological overview.

Classification of Mineral Resources and Ore Reserves is an essential component of Resource/Reserve estimation, and is one of the most important responsibilities of the Competent Person. When carried out appropriately, it accurately conveys the Competent Person’s confidence in the estimates to those who need to make decisions which depend on the estimates, but who have less familiarity with the deposit than the Competent Person.

Mineral resource and ore reserve classification defines the risk associated with quoted resource tonnes and grades, allowing the interested party to make a judgement as to the ‘worth’ of the resource statement. The JORC Code and Guidelines (1992) are now well entrenched as the foundation upon which gold and base metal deposits in particular are publicly reported. There are three categories of resource, namely Measured, Indicated or Inferred reflecting decreasing levels of confidence. The ore reserve, that is the economically mineable part of the resource, is classified as Proven or Probable and can only be drawn from the Measured and Indicated resource categories. <...>

The Australasian Code for reporting of Mineral Resources and Ore Reserves (JORC Code) was updated in 1999 (JORC 1999). This paper has been written as an update of Snowden (1996 and 1997) to recognise the large amount of experience with the use of the JORC Code gained by industry over the last four years, and describes the latest developments in technology and toolkits for risk classification.

So much work has been done in recent years using geostatistics to solve practical problems that we no longer have to apologise for nor justify the method. The method is as good as the practitioner, which goes, after all, for any technical application. There have been enough case studies now to show that almost any orebody, simple or complex in structure, which has a definable spatial continuity, will be amenable to geostatistical evaluation given that it is suitably sampled.

Австралазийские Нормы и Правила по составлению отчетов о минеральных ресурсах и запасах руды ('Нормы и Правила JORC ' или НиП) устанавливают минимальные стандарты, рекомендации и руководства по подготовке отчетов по результатам изысканий, минеральным ресурсам и запасам руд в Австралазии (Океании).

 The Australasian Code for Reporting of Mineral Resources and Ore Reserves (the ‘JORC Code’ or ‘the Code’) sets out minimum standards, recommendations and guidelines for Public Reporting of exploration results, Mineral Resources and Ore Reserves in Australasia. It has been drawn up by the Joint Ore Reserves Committee of The Australasian Institute of Mining and Metallurgy, the Australian Institute of Geoscientists and the Minerals Council of Australia. The Joint Ore Reserves Committee was established in 1971 and published a number of reports which made recommendations on the classification and Public Reporting of Ore Reserves prior to the first release of the JORC Code in 1989. <...>

The Australasian Institute of Mining and Metallurgy (The AusIMM) has been one of the principal organisations behind the JORC Code, which has been adopted by the Australian Stock Exchange and the Australian Securities commission as the standard for reporting mineral resources and ore reserves. This is now starting to be recognised as the international standard, with the UK, the USA and Canada all examining some form of the JORC Code for their resource and reserve reporting guidelines. The AusIMM has now further taken the initiative to produce a major volume covering all aspects of world’s best practice in Mineral Resource and Ore Reserves estimation. This prestigious volume will be published in the year 2000. <...>

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.  <...>