Dilution can be calculated in several ways, depending on the context and the stakeholder involved.
It is essential to clearly define which approach is being used to avoid costly misinterpretations.
- To a metallurgist, dilution is seen as the proportion of waste material in the total feed sent for processing. It is calculated as:
Dilution(%)= (mass of waste*100)/ (mass of ore + mass of waste) (1)
- To a mining engineer, dilution is often viewed as an increase in tonnage, and expressed as:
Dilution(%)= (mass of waste*100)/ (mass of ore) (2)
Both formulas (1) and (2) typically treat waste as barren, even though in reality, waste may still contain some payable mineral content, which can lessen the economic impact of dilution.
- Dilution can also be expressed in terms of grade reduction, as follows:
Dilution(%)= (resource grade- diluted grade)*100/ (resource grade) (3)
Each method of calculating dilution is valid, but it is essential to clearly define which approach is being used to avoid confusion.
For example, consider 100 tonnes of ore with a grade of 10%, mixed with 10 tonnes of material grading 4%. The resulting blend totals 110 tonnes at a diluted grade of 9.127%. Without clarifying the method of dilution calculation, misinterpretations can clearly occur.
Equation (1) gives: 10t x 100 / 110t = 9.1% dilution.
Equation (2) gives: 10t x 100 / 100t = 10% dilution.
Equation (3) gives: (10 – 9.127)t x 100 / 10t = 8.7% dilution.
Text rights: (McCarthy, n.d.)
Text source: McCarthy, P. L. (n.d.). Mining Dilution and Losses in Underground Mining.
