Calculate the Marginal Cut-Off Grade or the Cut-Over Grade

Strategy schedules provide a mechanism for cut-off grade optimisation where blocks are transported to different destinations based on the amount of ore they contain. Cut-off grade optimisation is based around a breakeven point after which a profit can be made. This point is called the marginal cut-off grade for single process set ups, or the cut-over grade for set ups with more than one process. The marginal cut-off grade is calculated using the following formula.

, where Pc1 = processing cost for process 1 ($/tonne), rec1 = direct recovery for cost for process 1 (%), P = price ($ per unit) and Sc = selling cost ($ per unit).

This equation is valid for set ups with one process.

For set ups with two processes, the following equation would be used.

, where Pc1 = processing cost for process 1 ($/tonne), Pc2 = processing cost for process 2 ($/tonne), rec1 = direct recovery cost for process 1 9%), rec2 = direct recovery cost for process 2 (%), P = price ($ per unit) and Sc = selling cost ($ per unit).