When an orebody is mined it is inevitable that some of the mineralized material is not mined but left behind in the pit. The loss of this material reduces the overall tonnage of material available to be sent to the plant and the loss of grade reduces even more the diluted grade of the reserve.

Recovery of mineralized material is lowered in a number of ways depending upon the mining method chosen. In open pit mines, the large excavation equipment will not be able to discriminate between the waste and ore materials resulting in some of the mineralized material being left in the pit. In underground mines, mineralized material may not be broken during blasting and is particularly the case for indirect mining methods in large stopes.

The prediction of recovery is more art than science. Tests of the friability of the waste rock, the presence of open fractures and joint sets and differences in specific gravity are all important elements in the prediction of recovery in underground mines. It is also important to look for similar types of operating mines and determine their experience with dilution using these results as a prediction of dilution in the new mine.

It can be appreciated that the calculation of a mining reserve must include some element of recovery as the loss of mineralized material is inevitable. Most of the reserve definitions accepted by modern securities regulators include recovery and an estimate for reserves which does not include this will not be accepted for publication.