Estimating bulk density for mineral resource reporting

CIM Journal, Vol. 5, No. 2, 2014

G. J. Arseneau
SRK Consulting (Canada) Inc., Vancouver, British Columbia, Canada

Abstract Mineral resource statements are reported as tonnage (volume × density) and grades. Effort is expended to accurately estimate the volume and grade, but accurately determining bulk density is often overlooked. Oversimplification of density modelling can result in potentially serious errors in tonnage estimates and over- or underestimation of metal content. A reliable bulk density model requires an adequate database and a good understanding of density variability, along with grade and geology. In this paper, the author summarizes density measuring techniques, draws on examples of simple and complex grade-variable density domains, and discusses improved approaches for minimizing density estimation errors.
Keywords: Bulk density, Specific gravity, Resource estimation, Mineral resources
Résumé Les déclarations de ressources minérales sont exprimées en termes de tonnage (volume x densité) et de teneurs. De grands efforts sont consentis pour estimer le volume et la teneur de manière précise mais la détermination de la masse volumique apparente est souvent négligée. Une simplification exagérée de la modélisation de la densité pourrait engendrer de sérieuses erreurs potentielles dans les estimés de tonnage et conduire à la sur- ou la sous-estimation du contenu en métaux. Un modèle fiable de détermination de la masse volumique apparente exige une base de données adéquate et une bonne compréhension de la variabilité de la densité, ainsi que de la teneur et de la géologie. Dans le présent article, je résume les techniques de mesure de la densité, je donne des exemples, simples et complexes, de domaines de densité à teneur variable et je traite aussi d’approches améliorées pour minimiser les erreurs d’estimation de la densité.
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