The cumulative % assay of the floats or sinks is plotted against the cumulative % weight of the floats or sinks.
These curves indicate cumulative assay that the cumulative floats or sinks will have at a particular S.G. of separation. They are used in conjunction with the S.G. curve and can thus predict the weights and assays of the two products of separation at any S.G. Conversely the S.G. of separation can be found for a desired of concentrate or tails.
Cumulative Assay of Sinks Curve
At an S.G. lower than that of the lightest mineral, all the material sinks. Therefore at 100% inks, the cumulative % assay of the sinks will equal the head assay. As the cumulative weight of sinks tends to zero, their assay will tend to that of the richest particle which, if any of the particles are completely liberated, will equal the assay of the heavy mineral.
Cumulative Assay of Floats Curve
At an S.G. greater than that of the densest component, the assay of the cumulative floats will equal the head assay. As the weight of the floats tends to zero, the cumulative assay will tend to the lowest possible assay unless the valuable component is present in both low and high S.G. forms. The minimum assay will equal zero only if the light mineral exists in a completely liberated form.