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Insights from our peer-reviewed journal | Compiled by Megan Skrip - 10 November 2026
Although new software can make generating reports faster, thoughtful consideration is still required to ensure accuracy.
Many people use a single pit surface to create grade-tonnage reports at different cut-off grades (left), which often yields undesired results, but using nested pit shells (right) produces more representative results. Courtesy of Renan Lopes/created with ChatGPT
This study showed that failing to constrain volumes when generating sensitivity tables can lead to substantial overestimations of a resource.
“Grade-tonnage sensitivity tables and accompanying charts are commonly created during mineral resource estimation,” said lead author Reno Pressacco, associate principal geologist with SLR Consulting (Canada) Ltd. Such tables are important for understanding how a mineral resource may vary according to a range of parameters, including metal prices and operational costs.
“Unfortunately, the methods used to create these tables do not necessarily yield the correct results,” Pressacco said. For example, open-pit mines may simply vary the cut-off grade within a single pit shell, rather than generate separate pit shells for each cut-off grade. “After years of observing this issue in practice,” he said, “we assembled a series of case studies that clearly demonstrate the problem and provide a practical framework for preparing mineral resource sensitivity tables.”
By examining three hypothetical gold mines, the researchers showed that not using nested pit shells at an open-pit mine can inflate estimates of gold content by more than 100 per cent. Similarly, not constraining volumes at an underground mine fails to account for spatial continuity of blocks and internal dilution, overestimating gold content in their study by up to 35 per cent.
The CIM Journal is a quarterly digital publication for peer-reviewed technical papers available to all CIM National Members as a membership benefit and to non-members for a fee. Papers cover all facets of the mining and minerals industry, including geology, mining, processing, metallurgy, materials, maintenance, environmental protection and reclamation, mineral economics, project management, health and safety, risk management, research and development, operations, and regulatory practices and issues.
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