How does a mill cutoff grade differ from a mine cutoff grade?

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mineral deposit The relationship between hot springs and epithermal veins.

In the context of a mineral deposit, the distinction between mine and mill cutoff grades is based on the stage of the extraction process and the associated costs:

Mine Cutoff Grade: This represents the minimum concentration of a valuable mineral required to make the act of mining the material profitable. If the grade falls below this threshold, it is not economically viable to extract the material from the ground.1
Mill Cutoff Grade: This applies to material that has already been extracted. It is the minimum grade required to make the subsequent mineral processing of that material profitable. If the grade is below this level, processing the material would result in a loss.1

Essentially, the mine cutoff grade determines whether material should be removed from the deposit, while the mill cutoff grade determines whether already-mined material should be sent to the processing plant or treated as waste.1