A column leach test is a laboratory simulation of heap-leach operation. Crushed ore is loaded into a vertical column (0.3–3 m diameter), cyanide solution is dripped from the top to mimic field irrigation, and pregnant solution is collected at the base. The test runs for weeks to months and produces the critical data for heap-leach plant design — heap height, irrigation rate, cycle time, and ultimate recovery.
Why Columns vs Bottle Rolls
Bottle roll tests dissolve ore in agitated solution — recovery is high because every grain is exposed. But a heap leach pile is static, with solution percolating through bulk ore. Recovery and kinetics are different. Column tests reproduce the field geometry — gravity-fed percolation, channeling effects, agglomerate stability — that bottle rolls cannot.
Test Parameters
Column diameter (0.3 m bench up to 3 m large-scale), packed height (matches the proposed heap lift, typically 6–30 m), irrigation rate (8–15 L/h/m² typically), cyanide concentration (matches proposed plant operation), and total leach cycle time (often 60–180+ days). Each variable can be tested in parallel columns.
Duration
Quick-look programs run 4–8 weeks. Bankable feasibility-level testing runs 90 days to 6+ months. Multi-season pilot operations sometimes run multiple years to validate ore variability across the deposit.
What You Get
Recovery vs. time curve — typically rising rapidly in the first 30 days then asymptoting. Cumulative cyanide consumption. Solution chemistry evolution (Au, Ag, pH, free CN). Solid residue analysis to verify mass balance. This data drives the bankable engineering estimate.
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