Recovery rate (or recovery percentage) is the proportion of contained metal that actually ends up in saleable form after processing. A heap leach with 80% gold recovery means 80% of the gold contained in mined ore is converted to doré bars; 20% is left in heap residue, tailings, or process losses. Recovery is one of the most economically critical parameters in any mining project.
How Recovery Is Calculated
For heap leach: Au recovered in doré ÷ Au contained in stacked ore × 100. For mill operations: Au in concentrate (or doré) ÷ Au in mill feed × 100. The denominator depends on assay of the feed; the numerator on metal-balance reconciliation. Reconciling these two over a quarter or year is a core operations-engineering discipline.
Typical Ranges
Heap leach gold: 60–85% depending on ore character, lift height, and leach time. Heap leach silver: often lower, 30–70%, because silver mineralogy is harder to leach. Milling CIL/CIP: 90–96% for free-milling gold ores. Refractory ores: 30–60% direct recovery — usually require flotation + roasting or POX.
Variables That Drive Recovery
Particle size after crushing, leach time, irrigation rate, cyanide concentration, lime addition, ore mineralogy, lifts thickness, climate (especially temperature), and uniformity of solution distribution. Every one is a design variable established by laboratory testing.
Why It's Worth Optimizing
A 1% recovery improvement on a 20,000 TPD operation with 1 g/t feed = 200 g/day extra gold = ~$13,000/day = ~$4.7M/year at current gold prices. Recovery optimization is one of the highest-leverage focus areas in any operating plant — and a routine subject of KCA's operations review service.
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