High-grade gold or copper ore contains more of the target metal per tonne of mineralized material, but “high-grade” does not by itself mean a mine will be profitable. Mine economics depend on how much metal can be recovered and sold, the costs and method of extraction, the ore’s processing characteristics, and the assumptions used to define economically mineable material.
What does ore grade measure?
Grade is the concentration of a target commodity in a given weight of mineralized material. Gold grade is generally reported in grams per metric tonne (g/t); copper grade is generally reported as a percentage. These units describe different concentrations and should not be compared directly. The SEC-hosted 2025 reserves and resources glossary describes these conventions and the calculation of contained metal.
Contained metal is estimated by multiplying the material’s tonnage by its grade. It is not the same as the metal a mine will ultimately produce: some metal may not be recovered during processing, and the amount recovered is not necessarily the amount sold.
A simple way to read a grade figure
A report stating a grade gives a concentration, not a profit estimate. To understand its significance, check the units, the amount and classification of material to which it applies, and the assumptions behind the project’s cut-off grade, recovery, processing route and costs.
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There is no single grade that makes every gold or copper deposit “high-grade” in an economic sense. The relevant cut-off grade depends on a deposit’s conditions and the economics assumed for it. Newmont’s 2024 Mineral Reserves release explains that cut-off grades can vary with prevailing economic conditions, mineability, by-products, how amenable the ore is to extraction, and available milling or leaching facilities.
A grade that supports processing in one operation may not do so in another. The comparison is meaningful only alongside the project-specific assumptions: “high” is relative to the deposit, mining plan and economic conditions, not a universal benchmark.
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How grade affects mine economics
More metal in each tonne can increase the potential value of that tonne. Whether it improves the mine’s economics depends on the metal that can be recovered and sold, set against the costs and constraints of getting it out of the ground and processing it.
Recovery and ore characteristics
Metallurgical recovery is the share of metal extracted from ore through the chosen process. Recovery varies by deposit and production process, so two ores with the same reported grade need not yield the same amount of recovered metal. Mineralogy and ore type affect which process is suitable and how effectively it can extract the metal. Newmont identifies grade, recovery and ore type among the factors relevant to reserve price sensitivity.
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Mining, processing and waste
Mining and processing costs influence whether the recovered metal’s value can cover the expense of producing it. The waste-to-ore ratio also matters: a project may need to move substantial waste to reach the material it processes. Mining method, mineability and the availability of processing facilities all contribute to the project-specific calculation, rather than grade acting as a stand-alone measure.
By-products and economic assumptions
Other saleable metals can contribute by-product credits and affect the cut-off calculation. Prevailing economic conditions also matter. A reported cut-off should therefore be read with its associated assumptions rather than treated as an intrinsic, permanent property of the ore.
What a cut-off grade tells you
A cut-off grade is a concentration threshold used to decide how material is treated in the applicable mining context. Material meeting the threshold may be directed to processing; material below it may be treated as waste under that plan. The SEC-hosted glossary defines the material-destination concept, while Newmont’s disclosure explains why the threshold varies with project conditions.
The cut-off is not a universal line between valuable and worthless rock. It is part of an economic and operational plan: changing assumptions about costs, recovery, by-products or facilities can change which material qualifies for processing.
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Resource and reserve labels change what a grade claim means
A grade figure should be read with its resource or reserve classification. A Mineral Resource is a geological estimate assigned a confidence category; it should not automatically be read as material that can be profitably mined. A Mineral Reserve represents the economically mineable portion of qualifying resources after relevant modifying factors and mine planning are applied.
The ASX technical report on Ore Reserve reporting defines an Ore Reserve as the economically mineable portion of Measured and/or Indicated Mineral Resources. An SEC-hosted technical disclosure on resource and reserve definitions notes that reserve estimates incorporate dilution and losses, and states that an Inferred Resource cannot be considered when assessing economic viability under the referenced framework. A resource estimate—especially one in a lower-confidence category—is not an established reserve or proof of a viable mine.
How to compare grade claims responsibly
When comparing projects or disclosures, use the whole set of assumptions rather than ranking them by grade alone. Check that the figures cover comparable material and periods, and note the following:
- Grade and units: identify whether gold is reported in g/t or copper in percent, and avoid comparing different units as if they were equivalent.
- Classification and date: distinguish a resource estimate from a reserve and note the effective date of each estimate.
- Cut-off and economic assumptions: look for the stated cut-off grade and the conditions used to set it.
- Recovery and process: check the recovery assumptions and the milling, leaching or other processing route.
- Costs and mine plan: consider operating costs, mining method, mineability and the waste-to-ore ratio.
- Ore type and by-products: account for processing characteristics and any credits from other saleable metals.
A project-specific SEC-hosted technical disclosure illustrating cut-off assumptions shows why such figures belong to the project and its stated assumptions; its numerical inputs should not be generalized to other mines.
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