By the YELI Technical Team · Updated August 2026 · 8 min read
Short answer: When gold loss in your CIL tailings rises, the first 10-minute test splits the problem in two: assay the tailings solution and the tailings solids separately. High soluble gold (in solution) means gold is dissolving but not being adsorbed — a carbon circuit problem (activity, concentration, fouling) or preg-robbing ore. High solid gold means gold never dissolved or re-precipitated — a leaching problem (cyanide, pH, oxygen, grind, contact time). One split sample tells you which half of the plant to investigate, before you spend days chasing the wrong cause.
Every gold plant fights tailings losses. The expensive mistake is guessing: replacing carbon when the problem is cyanide, or adding cyanide when the carbon is dead. The split assay removes the guesswork. Here is the field method, the numbers to watch, and what each result means.
1. The Split Assay: One Sample, Two Numbers
Take a tailings slurry sample and split it:
• Solution (soluble) gold — filter the liquid and assay the clear solution. This tells you how much dissolved gold is leaving the plant un-adsorbed.
• Solids gold — assay the filtered solids. This tells you how much gold is locked in the ore and never made it into solution (or re-precipitated).
Read the pair together: the split between solution gold and solids gold is the fastest diagnostic signal you have.
2. What Each Result Means
| Symptom | Where to Look | Likely Cause |
|---|---|---|
| High solution gold, normal solids | Carbon circuit | Carbon activity low, concentration low, fouling/poisoning, or preg-robbing ore |
| High solids gold, normal solution | Leaching circuit | Low free cyanide, pH/DO off, coarse grind, short retention, preg-robbing |
| Both high | Both | Multiple issues — work the carbon circuit first (it is usually faster to fix) |
| Gold on carbon fines in tailings | Carbon hardness | Soft carbon grinding into fines — check delivered hardness vs COA |
3. The Carbon-Circuit Checklist (High Solution Gold)
1. Carbon activity — take loaded and barren carbon samples. If regenerated carbon activity dropped below ~80% of fresh, organic fouling or inorganic scale is blinding the pores (see our poisoning guide).
2. Carbon concentration — confirm carbon density per tank (typical 15-25 g/L). Low concentration leaves dissolved gold un-adsorbed.
3. Fines and degradation — check the elution column bottom and tailings stream for carbon fines. Excessive degradation means impeller/pump wear or substandard carbon hardness.
4. Acid wash and regeneration — verify acid wash efficiency (removes calcium scale) and kiln temperature in an oxygen-free atmosphere. Incomplete regeneration leaves pores clogged.
4. The Leaching-Circuit Checklist (High Solids Gold)
1. Free cyanide — measure in Tank 1 and Tank 2. If free CN drops below the critical level, gold stops dissolving and leaves as solid.
2. pH and dissolved oxygen — keep pH in the target lime range and DO adequate. Oxygen-consuming minerals or poor aeration degrade leach kinetics severely.
3. Cyanicides and competitor ions — elevated copper, nickel or arsenic consume cyanide and compete for adsorption. Assay solution metals.
4. Grind size and retention — check cyclone overflow; coarser grind reduces liberation, and higher throughput cuts retention time below the design minimum.
5. Track the Numbers Weekly
The value of the split assay is trend. Log solution gold and solids gold weekly — even a small rising trend is an early warning. Compare against your own baseline; "normal" varies by ore, but a change from your stable baseline is always a signal.
We Help Plants Find Where the Gold Is Going
YELI Carbon is a coconut shell activated carbon manufacturer in Longyan, Fujian — 20+ years, gold-grade lines, hardness 98%+ (98% available), COA with every batch. If your tailings numbers are drifting, send us a sample of your current carbon and we will run a side-by-side test against ours: iodine, hardness, gold adsorption. See the real gap before you order.
Request a Sample Test →The Bottom Line
Tailings gold loss is not a mystery once you split it: solution gold points to the carbon circuit, solids gold points to leaching. Run the split assay first, then follow the right checklist. For more, see our recovery drop guide and preg-robbing diagnosis.
FAQ: Tailings Gold Loss
Assay the tailings solution and the tailings solids separately. High soluble (solution) gold means gold is not being adsorbed — a carbon problem (activity, concentration, fouling) or preg-robbing. High solid gold means gold never dissolved — a leaching problem (cyanide, pH, grind, contact time). This split test is the first, fastest diagnosis.
Typical CIL plants target total tailings gold below 0.1 g/t, with soluble gold in solution below 0.01-0.02 ppm (depending on ore). If soluble gold is elevated while solids are fine, focus on the carbon circuit; if solids are elevated, focus on leaching. Compare against your own historical baseline first.
Solid gold in tailings means the gold never dissolved or was re-precipitated. Check free cyanide in the first tanks (should stay above the critical level), pH control, dissolved oxygen, grind size (coarse gold is slow to leach), and preg-robbing ore minerals. Carbon cannot fix gold that never enters solution.
Yes. Soft carbon grinds into fines during agitation and pumping; those fines carry adsorbed gold through the interstage screens and out with the tailings. This shows up as high solid gold or as gold attached to carbon fines in the tailings. Hardness 95%+ (ideally 98%+) minimizes this loss.