Grade Reconciliation is the process of comparing predicted mineral grades, tonnes, and contained metal from geological resource models or mine plans with the actual grades, tonnes, and metal recovered from mining, processing, and final product stages. It is a critical quality assurance tool used in all types of mining — bauxite, gold, iron ore, and diamond — to assess the accuracy and reliability of geological models, grade control procedures, and mining execution.
Reconciliation is typically performed at multiple stages: between the resource model and the grade control model, between the grade control model and mill feed data, and between mill feed and final production. Discrepancies identified during reconciliation, often expressed as reconciliation factors or ratios, reveal systematic biases in sampling, assaying, geological interpretation, or ore loss and dilution during mining.
In gold mining, reconciliation is particularly important due to the high value of the commodity and the significant financial impact of even small grade differences. In iron ore, reconciliation compares predicted and actual iron, silica, and alumina percentages. In diamond mining, it tracks carat recovery against modelled estimates. Good reconciliation performance indicates that geological models are fit for purpose and that mining is proceeding as planned.
Poor reconciliation triggers investigations and model updates. Regular reconciliation reporting is also a requirement of many financial institutions, regulators, and stock exchange listing rules.