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What does ore grade measure in a mineral deposit?

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mineral deposit The relationship between hot springs and epithermal veins.

In the context of a mineral deposit, ore grade measures the concentration of a valuable mineral within the ore.1

This metric is essential for determining the economic viability of a mining operation. Because grade can vary significantly throughout a deposit, it is used to distinguish between profitable ore and waste material based on several key thresholds:1

Mine cutoff grade: The minimum grade required to make mining the mineral profitable.1
Mill cutoff grade: The minimum grade required to make processing already-mined material profitable.1
Break-even grade: The specific grade at which the costs of mineral processing and extraction are exactly equal to the revenue generated by the commodity.1

Material with a grade higher than the break-even point is considered ore, while material falling below this level is classified as waste. Consequently, determining whether a deposit constitutes an exploitable reserve requires balancing these grade measurements against the expected market price of the commodity and the specific costs associated with the chosen mining system.1