Modern tailings recovery starts by identifying the form of the gold in the material and then selecting the recovery family that best recovers it. The four method families are gravity concentration, flotation, carbon-in-leach, and hybrid gravity-leach circuits.
How does gravity concentration recover tailings gold?
Gravity concentration recovers the free gold fraction that is coarse enough to separate by density. In tailings retreatment, this method is applied after classification and before the main leach circuit. It is most effective when the material contains visible or liberated gold particles that gravity separators can capture. Modern tailings work has largely moved from older jigs and shaking tables to centrifugal concentrators such as Knelson or Falcon units, which use centrifugal force rather than gravity alone and can recover much finer free gold as a result. The full mechanism, and the testwork that determines whether it will work on a specific dump, is covered on gravity recovery of gold from tailings.
Gravity recovery is the lowest-cost first step because it removes gold that would otherwise consume cyanide or reduce flotation performance. That is why many operators use gravity first and then send the tailings to the next stage.
When is flotation the right method?
Flotation is the right method when a significant portion of the gold is associated with sulphide minerals such as pyrite or arsenopyrite. It works by conditioning the slurry with a collector reagent, commonly a xanthate, that makes the sulphide (and the gold locked inside it) hydrophobic so it attaches to air bubbles and rises to the surface as concentrate, leaving the barren gangue behind. The full mechanism is covered on flotation of gold tailings.
For Ghanaian tailings, flotation is often selected when compositional studies show locked gold in sulphides or when the material is fine and the free-gold proportion is low. It also helps to upgrade the feed before leaching, improving overall recovery, exactly the sequencing worked through on sulphide flotation before leaching.
How does carbon-in-leach (CIL) work on tailings?
Carbon-in-leach works by dissolving gold from fine particles and surface-bound gold in the presence of cyanide, while activated carbon is mixed with the slurry to adsorb the dissolved gold as it forms. This simultaneous leaching and adsorption is efficient for the gold that gravity and flotation cannot recover. Once loaded, the carbon is stripped in an elution circuit, typically a Zadra or AARL process, to produce the gold-bearing solution that ultimately goes to electrowinning.
CIL is most appropriate for tailings with fine, preg-robbing gold or when the gold is dispersed in a mineral matrix. It is the standard final stage for a tailings retreatment flowsheet, especially when the material has already been classified and cleaned by upstream circuits.
What is a combined gravity-leach flowsheet?
A combined gravity-leach flowsheet uses gravity concentration first, then passes the remaining material to flotation or CIL. This strategy recovers the easy gold first and then draws value from the finer or locked fraction.
In practice, a hybrid flowsheet can look like gravity → flotation → CIL or gravity → CIL with a scavenger stage. The exact layout depends on the material’s deportment and the testwork results, but the principle is always the same: use multiple methods to maximize recovery. This method taxonomy is what a physical gold processing plant for tailings is built around, and the full logic behind combining stages is worked through on combined gravity-leach flowsheets.
How do you choose between methods?
The method choice is made by matching gold deportment, grade, and mineralogy to the process family, using roughly the pattern in the matrix below.
| Deportment | Grade context | Mineralogy | Recommended route |
|---|---|---|---|
| Free, coarse gold | Any grade where gravity capture is feasible | Low sulphide, quartz-dominant | Gravity concentration |
| Locked in sulphides | Grade concentrated in the sulphide fraction | Pyrite, arsenopyrite present | Flotation |
| Fine or surface-bound | Low grade spread through fine particles | Oxide-dominant or weathered | Carbon-in-leach |
| Mixed forms | Any grade with more than one gold mode present | Mixed oxide-sulphide | Hybrid gravity-leach |
Free gold points to gravity, sulphide-associated gold points to flotation, and fine or preg-robbing gold points to carbon-in-leach. When the material contains multiple gold forms, which is the normal case, a hybrid method is usually the best choice. That's why technical teams run diagnostic testing before finalizing the flowsheet, building on the composition and history covered on gold tailings composition and why old tailings still contain gold.
What happens when gold won't respond to any standard method?
When gold doesn't respond to gravity, flotation, or CIL, the material may be refractory, and it needs more advanced treatment such as ultra-fine grinding, oxidative pre-treatment, or pressure oxidation, the three routes worked through on refractory gold in tailings: roasting, BIOX and POX. In most Ghanaian tailings cases, though, the standard methods are sufficient once the material is properly characterized. If a deposit does require refractory treatment, that's a separate technical path that usually changes the project economics significantly. For most tailings retreatment opportunities, the hybrid gravity-leach approach remains the default, because it balances cost and recoverability better than any single method on its own.
Where the method choice actually comes from
The deportment, grade, and mineralogy data that this selection matrix runs on come from real testwork, starting with fire assay to establish grade and followed by diagnostic leach and flotation testing. No method should be chosen from composition data alone.
Cyanide alternatives and the ESG angle
Where cyanide use is a concern for permitting or community reasons, alternative lixiviants exist for the leach stage, most notably thiosulfate leaching, though they typically come with slower kinetics, higher reagent cost, or lower recovery on certain ore types, which is why cyanide remains the default despite the alternatives being technically viable. That broader environmental framing is covered on what sustainable mining actually means.
How this becomes a physical plant
Once a method or hybrid flowsheet is selected, it gets built into an actual plant, unit by unit, on gold processing plants for tailings.