Grade

The amount by mass of metal or mineral in an ore, usually expressed as troy ounces per ton (oz/ton) or grams per tonne (g/tonne) for precious metals and as a percentage or parts per million for other minerals.

(i) Reserve grade: estimated grade of an orebody based on the reserve calculation.

(ii) Cut-off grade: the lowest grade of mineralized material considered economic. Used in the calculation of ore reserves in a given deposit and for determining waste from ore in mining.

(iii) Mill (head) grade: the grade of mined ore going into a mill for processing. Usually lower than reserve grade because of dilution.

(iv) Recovered grade (yield): the actual grade recovered from an ore, determined after processing.