Here is the formula you need to calculate Metal Recoveries using Assays only. You have two products/concentrates. This will save you time in your metallurgy accounting calculations. Some call the same formula the two (2) product other the three (3) product formula.
Frequently, a concentrator will mill a complex ore requiring the production of two separate concentrates, each of which is enriched in a different metal or valuable mineral, plus a final tailing acceptably low in both constituents. Formulas have been developed which use the feed tonnage and assays of the two recovered values to obtain the ratios of concentration, the weights of the three products of separation, and the recoveries of the values in their respective concentrates.