In the first part of this paper, the principal sources of dilution during
underground evaluation and mining are discussed, then definitions of ore
dilution currently in use are analysed. These definitions vary depending
on the authors. Ten different analytical expressions of dilution percentage
currently exist. It is demonstrated, with the help of a numerical example
for a given mining condition, that dilution percentage results vary
considerably and that they depend on the definition used. This situation
makes it difficult to compare different results regarding the dilution
problem, often because some of the terms used are contradictory. A new
ore dilution evaluation methodology is proposed, replacing the ten
different analytical expressions by only two: the planned dilution factor
related to the stoping selectivity, done at the mine planning level, and the
additional dilution factor related to the efficiency of the dilution control
measures during stoping operations. The conclusion shows that the use of
this methodology would be a definitive asset in planning, in stoping
operations follow-up, and in future costs comparison studies between
mining operations.