Some common flaws encountered in mineral resource estimation and how to avoid them

ABSTRACT

Preparation of a mineral resource estimate (MRE) is an essential component in the mining cycle, as errors that occur in an MRE will affect all following steps that rely upon its accuracy. Over the course of many decades, SLR Consulting (Canada) Ltd. and predecessor Roscoe Postle Associates have observed a number of common errors that occur at all stages of the workflow. The purpose of this paper is to share some of SLR’s experiences relating to the errors encountered during the preparation of MREs and to present some solutions for avoiding these errors. SLR observes that the source of many of the flaws is the result of the level of knowledge, experience, judgment, or expertise by the practitioner of the fundamental principles of mineral resource estimation and with the software package used in preparing the MRE. Attention to detail and adherence to high quality standards throughout the estimation process is the first step in avoiding many of the errors. A critical item for all practitioners to bear in mind is that they are accountable and bear the ultimate responsibility for all aspects of their work.

RÉSUMÉ

La préparation d’une estimation des ressources minérales (MRE, de l’anglais mineral resource estimate) est une composante essentielle du cycle minier, car les erreurs qui se produisent dans un MRE affecteront toutes les étapes suivantes qui en dépendent de son exactitude. Depuis plusieurs décennies, SLR Consulting (Canada) Ltd et son prédécesseur Roscoe Postle Associates ont observé un certain nombre d’erreurs courantes qui se produisent à toutes les étapes du travail. Le but de cet article est de partager une partie des expériences de SLR relatives aux erreurs rencontrées lors de la préparation des MRE et présenter quelques solutions pour éviter ces erreurs. SLR observe que la source de beaucoup d’erreurs est le résultat du niveau de connaissances, d’expérience, de jugement ou d’expertise du praticien des principes fondamentaux de l’estimation des ressources minérales et avec le logiciel utilisé dans la préparation du MRE. Le souci du détail et le respect de normes de qualité élevées tout au long du processus d’estimation est la première étape pour éviter de nombreuses erreurs. Un élément essentiel que tous les praticiens doivent garder à l’esprit est qu’ils sont responsables et portent la responsabilité ultime de tous les aspects de leur travail.

KEYWORDS:

• Block model validation
• Estimation errors
• Fatal flaws
• Grade smearing
• Mineral resource
• Reasonable prospects
• Unsampled intervals

MOTS CLÉS:

• erreurs d’estimation
• erreur fatale
• teneur exagérée
• intervalles non échantillonnés
• prospects raisonnable
• ressource minéral
• validation du modèle de bloc

ACKNOWLEDGMENTS

The authors thank Marilen Miguel and the Professional Geoscientists Ontario for their inspiration to write this paper. We thank Jason Cox and our colleagues at SLR Consulting (Canada) Ltd., including William E. Roscoe, Sean Horan, Charles Parkinson, and Renan Lopes, for their support and assistance in the preparation of this paper. We are also grateful to James Barltrop (Scotia Capital Inc.), Dhaniel Carvalho (Glencore Zinc Technical Services), John Korczak (Glencore-Sudbury Integrated Nickel Operations), Lucy Potter (Rio Tinto), David Ross (Marathon Gold Corporation), and John Sullivan for sharing their knowledge and assistance in providing suggestions on the draft copy of this paper.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

REVIEW STATEMENT

This article was reviewed and approved for publication by the Geological Society of the Canadian Institute of Mining, Metallurgy and Petroleum.

ETHICS APPROVAL AND CONSENT TO PARTICIPATE

There are no ethical issues associated with this manuscript.

Additional information

Notes on contributors

R. Pressacco

Reno Pressacco, MSc (A), PGeo, is an Associate Principal Geologist with SLR with more than 37 years of experience in industry, government, and consulting. He is a member of the CIM Mineral Resources and Mineral Reserves standing committee and the United Nations Minerals Working Group committee. He is a contributing author to a number of the CIM Best Practices Guidelines and in 2020, received the CIM Robert Elver Mineral Economics Award.

P. Landry

Pierre Landry, BScH, PGeo, is a Principal Geologist and Valuations Lead with SLR. His work is primarily focused on geological evaluations of exploration projects and mining operations. Pierre frequently draws on his operational and corporate development experience to provide technical advice to his clients. He studied geology and economics at Queen’s University and is a Professional Geologist in the province of British Columbia.

L. Evans

Luke Evans, MSc, PEng, is a Principal Geologist with SLR. He has approximately 40 years of mineral industry and consulting experience, including more than 28 years with SLR, where he currently leads a team of more than 25 resource geologists. He has presented papers and short courses on resource estimation best practices, audits, pitfalls, and other topics.