Dilution is an unavoidable challenge in mining, but not all dilution is the same. Understanding the different types of dilution is key to improving ore recovery and reducing unnecessary costs.
Here is a breakdown of the main types of dilution:
Planned dilution refers to the rock with a lower mineralization content than the cut-off grade within stope limits. Unplanned dilution refers to the rock with a lower mineralization content than the cut-off grade that originates from outside the planned stope limits, for example by poor rock control, see schematics below which illustrates planned and unplanned dilutions(Dilution – SIX-S GmbH, n.d.).
Internal dilution occurs within a mining block when pockets of waste or low-grade material are enclosed by high-grade ore and cannot be separated during extraction. These inclusions are unavoidably mined along with the ore. The extent of internal dilution varies depending on deposit type and is largely influenced by lithological characteristics and grade distribution. In most cases, internal dilution is difficult if not impossible to avoid(2 New Messages, 2024).
External dilution refers to the inclusion of waste material located outside the orebody but mined within the same block. It is influenced by factors such as geological conditions, orebody shape, drilling and blasting techniques, equipment size, and the scale of operations. By clearly defining ore waste contact boundaries, selecting suitable equipment to ensure precise mining as well as following ore contacts closely during extraction are some strategies that can considerably minimize external dilution.
Identifying and minimizing the various types of dilution is fundamental to maximizing a mine’s value. Which type of dilution do you believe is the most challenging to mitigate effectively, and what strategies do you use to combat it?
Reference:
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2 new messages. (2024, October 23). https://groundhogapps.com/ore-dilution-and-quality-control/
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Dilution – SIX-S GmbH. (n.d.). Retrieved October 10, 2025, from https://www.six-s.com/knowledge-base/article/dilution/
