The success of any mining venture economically depends on the efficient extraction of the ore. This requires maximizing efficiency and minimizing waste, which become even more important considering the high volatility of the commodity prices and increased costs of extraction in such an industry. One of the most important factors for mining optimization is ore dilution, which adversely affects the financial well-being of the mine, revenue generation, and the production metrics.
It becomes necessary to understand the definitions of the key terms to comprehend this relationship. The definition of ore dilution is given as the inclusion of waste or lower grade ore below the cutoff grade within the extracted ore (Camara et al., 2020). The definition of the mine revenue is the amount of income earned from the sales of extracted ore by the mine. The All-in Sustaining Cost (AISC) per ounce is the financial term used for the cost of production of an ounce of metal.
The most immediate financial effect of ore dilution is the decline in the mine’s income. The combination of the sterile waste rock and the ore cause the ore grade at the mill to decline. As a result, the processing plant produces less metal per ton of rock. Importantly, an increase in the rate of ore dilution by 13% results in a 15% decline in revenue and significant shrinkage of the gross profit margin (Delentas et al., 2021).
Apart from cutting revenue, ore dilution increases the AISC per ounce directly. Extraction, transportation, and processing of the waste rock require the same amount of fuel, reagents, and labor as the high-grade ore. With rising costs and declining ounces of metal produced, the denominator in the formula for the cost per ounce becomes smaller. It leads to the rise in AISC, bringing the mine closer to its cut-off grade (Birch, 2022).
For this purpose, engineers use sophisticated spatial and economic modeling techniques. Short-term mine planning makes use of block models along with geostatistical simulation to determine the probability of dilution and compute the diluted grade. By linking this information to financial packages, the exact cost associated with the processing of the waste material is quantified.
In conclusion, the need to assess and quantify the economic effect of ore dilution becomes an imperative to ensure that a mine remains profitable. Unplanned dilution results in a double cost effect of not only reducing future earnings but also increasing AISC per ounce. With the use of accurate geologic modeling, mining companies will be able to estimate such losses.
References
Birch, C. C. (2022). Optimizing cut-off grade considering grade estimation uncertainty – A case study of Witwatersrand gold-producing areas. Journal of the Southern African Institute of Mining and Metallurgy, 122(7), 1–10. https://doi.org/10.17159/2411-9717/1403/2022
Camara, T. R., Scheffer Leal, R., & De Lemos Peroni, R. (2020). Accounting for operational dilution by incorporating geological uncertainties in short-term mine planning. DYNA, 87(213), 178–183. https://doi.org/10.15446/dyna.v87n213.83661
Delentas, A., Benardos, A., & Nomikos, P. (2021). Analyzing Stability Conditions and Ore Dilution in Open Stope Mining. Minerals, 11(12), 1404. https://doi.org/10.3390/min11121404
