Ore Grade

Ore grade is the concentration of a valuable component in mined material. It may refer to metal content, mineral content, energy content, chemical purity, or another recoverable property depending on the resource. Grade is often reported as percent, grams per tonne, parts per million, or a commodity-specific unit.

Grade is not the same as value. The value of mined material also depends on recovery, mineralogy, liberation size, deleterious elements, moisture, processing cost, transport cost, product specification, and market assumptions. A high-grade material can be difficult to process, while a lower-grade material may be useful if it is easy to recover or blend.

Engineering use

Ore grade drives block models, mine plans, cut-off decisions, blending, stockpile management, process control, production forecasts, reconciliation, and waste classification. It connects geology with mining, processing, economics, water use, tailings generation, and closure planning.

Sampling and uncertainty are central. Assay data represent limited samples of a variable deposit. Dilution, ore loss, sampling bias, moisture correction, scale effects, and short-term feed variability can make plant head grade differ from modelled grade.

Common mistakes

A common mistake is treating grade as a single deterministic value. In real deposits, grade varies spatially and measurement uncertainty matters. Another is optimizing mining only for grade while ignoring recovery, throughput, geotechnical limits, processing constraints, tailings behavior, and reliability. A strong grade review states sample basis, units, moisture basis, cut-off assumption, dilution, recovery, uncertainty, and reconciliation method.