How Gold Recovery Works in Modern Processing Plants
Every gold processing plant is judged by one number. It is not how much ore it treats, how big its mills are, or how modern its equipment looks. It is the recovery rate: the share of the gold in the ore that the plant actually manages to catch. A plant that recovers 95% of the gold it is fed throws away only 5% in its tailings. A plant that recovers 70% throws away nearly a third. That single percentage decides whether a mine makes money, and it is the number you will see quoted in almost every company report about a gold project.
This article explains what that number means, walks through the recovery stages of a modern plant as one journey, shows how recovery is actually measured and reported using a real testwork example, and explains why the number is never 100%. For the full step-by-step extraction chain this journey sits inside, from crushed ore at the plant gate to doré bars, see our guide to how gold is extracted from ore.
What “Gold Recovery” Actually Means
The recovery percentage: gold in vs gold out, the rest stays in the tailings
Gold recovery is a simple idea with a precise meaning. The plant assays the ore coming in (the head grade, measured in grams of gold per tonne of ore) and measures the gold it produces. The recovery rate is the percentage of the gold in the feed that ends up in the product. Everything that is not recovered reports to the tailings: the finely ground waste that leaves the plant and is stored in a tailings facility.
Imagine a plant fed with ore grading 2 grams per tonne. If it recovers 90% of that gold, it captures 1.8 grams per tonne and loses 0.2 grams per tonne to the tailings. That lost fraction is not a rounding error. Over millions of tonnes of ore, a few percentage points of lost recovery can be worth more than the entire cost of running the plant. This is why metallurgists treat recovery as the plant’s scorecard, and why companies report it so prominently.
Why this number matters more than the head grade alone
Beginners often focus on the head grade, and it is easy to see why: richer ore sounds like an easier business. But head grade alone says nothing about how much of that gold can actually be caught. A high-grade ore with gold locked inside sulfide minerals may surrender only half its gold to a standard plant, while a lower-grade ore with free, clean gold particles may give up more than 90%.
Investors and engineers therefore read the two numbers together. The head grade tells you how much gold is in the rock. The recovery rate tells you how much of it the plant can turn into saleable metal. A project is only as good as the combination of the two, and a recovery figure quoted without its ore type, test method and measurement basis is a number without context. Later in this article you will see how to read such figures properly. The same recovery idea also applies beyond ore, to a second feedstock: discarded electronics.
The Recovery Journey Through a Modern Plant
A modern gold plant does not catch gold in a single step. It runs the ore through a sequence of stages, each one designed to catch a different kind of gold, and each stage’s leftovers become the next stage’s feed. The diagram below shows the journey in order. The sections that follow explain what each stage contributes to the final recovery number.
Liberation first: crushing and grinding free the gold
Nothing can be recovered until the gold is freed from the rock around it. This is the job of comminution: crushing the ore, then grinding it in mills until it is a fine slurry. The goal is liberation, meaning the gold particles are physically separated from the waste minerals that surrounded them.
Liberation is the foundation of everything that follows. Gold that is still locked inside a grain of rock cannot be caught by gravity, floated, or dissolved. It will pass straight through the plant and report to the tailings, no matter how good the later stages are. Grinding finer frees more gold, but it also costs more energy and can create very fine particles that are harder to catch, so plants constantly balance fineness against cost and downstream performance.
Gravity recovery: catching the coarse free gold
The first recovery stage in many plants is gravity concentration. Coarse, free gold particles, typically larger than about 100 microns, are heavy enough to be separated from lighter rock simply by density, using shaking tables, jigs, spirals and centrifugal concentrators. Gravity recovery needs no chemicals, costs little to run, and catches the gold that is easiest to catch.
It has a clear limit: it is ineffective for very fine gold, which does not settle fast enough to be separated this way. That is why gravity is a first stage, not the whole flowsheet. Its product is usually a small, high-grade concentrate that goes on to further treatment, while the rest of the ore continues to the next stages. For a closer look at gravity separation itself, see our guide to gold washing.
Flotation: concentrating the sulfide-locked gold
After gravity, the ore often goes to flotation, the standard method for gold that is associated with sulfide minerals. In flotation, the ground slurry is mixed with reagents and air is blown through it. The sulfide particles, carrying their gold, attach to bubbles and rise into a froth that is skimmed off, while most of the waste rock sinks and is rejected.
Flotation does not produce finished gold. It produces a concentrate: a much smaller stream that holds most of the sulfide-associated gold, and which can then be treated further. Vendor guides describe flotation concentrates of typically 20 to 40 grams per tonne with a recovery rate of 85 to 93%, but that is a vendor-stated range from a single unreferenced source, not a verified fact, so treat it as an indication of what vendors claim rather than a universal figure. The real point of flotation in the recovery journey is concentration: it shrinks the problem, so that the expensive leaching stage only has to treat the gold-bearing fraction instead of the whole ore stream.
Leaching: dissolving what gravity and flotation missed
What gravity and flotation cannot catch is dissolved. In cyanide leaching, the ore slurry is mixed with a dilute cyanide solution, with oxygen, and the gold dissolves into the liquid. Leaching is the workhorse of modern gold recovery because it can reach fine gold that physical methods cannot, and it works on a wide range of ore types.
Leaching is also where the two best-known recovery routes, CIP and CIL, come in: they differ in whether the gold is leached first and then collected on carbon, or leached and collected at the same time. That comparison is covered in full in our article on CIP vs CIL gold processing, and it is not repeated here. For ores that are too low-grade for tank leaching, heap leaching, stacking the ore in heaps and irrigating it with cyanide solution, is sometimes used as an alternative recovery route, but it generally gives lower recovery over longer times and it is a subject of its own.
Capturing the dissolved gold: carbon adsorption or zinc precipitation
Once the gold is dissolved, it still has to be caught. The two standard capture routes are activated carbon adsorption, where the dissolved gold sticks to granules of specially prepared carbon, and zinc precipitation, known as the Merrill-Crowe process, where zinc powder displaces the gold from solution. Carbon adsorption is the more common route in modern tank plants; Merrill-Crowe is often used where the solution is clear and low in solids.
The detail of how activated carbon is made and specified belongs to a separate topic and is only mentioned here, because capture is one stage of the journey, not the journey itself. What matters for recovery is that this stage decides how much of the dissolved gold actually leaves the plant in solid form. Gold that stays in solution, or is lost in the barren solution after capture, is gold that the recovery number never sees.
From capture to doré: elution, electrowinning, smelting
The final leg of the journey turns captured gold into metal. Carbon loaded with gold is stripped in elution, the resulting rich solution is passed through electrowinning, where an electric current plates the gold out as a sludge, and that sludge is smelted into doré bars: semi-pure bars of gold and silver that are the plant’s saleable product.
These are hand-off steps, not recovery stages in themselves, but they complete the scorecard: the doré that leaves the plant is the numerator in the recovery calculation. The smelting and refining that turn doré into pure gold are covered in our guides to the gold smelting process and the gold refining process.
How Recovery Is Measured and Reported
Recovery is measured by comparing what goes in with what comes out: assays of the feed, the products and the tailings, reconciled over a period of time. In a running plant this is routine metallurgical accounting. In a new project, it is established by laboratory testwork, and that is where company reports get their recovery figures. A published testwork example shows exactly how such a figure is built, and why it must be read with care.
In July 2026, the ASX-listed explorer Mount Hope Mining reported Phase 1 metallurgical testwork on its Mt Solitary gold prospect: an indicative combined gold recovery of more than 98% using conventional gravity plus cyanidation. The headline figure is built from three measured parts. First, gravity-recoverable gold (GRG), the share of the gold that gravity concentration alone can catch, was 70.4%. Second, cyanide solubility of the gravity tailings, the share of the remaining gold that dissolves in cyanide, was 94.6%. Third, diagnostic work showed about 5% of the gold locked in sulfides and about 0.4% locked in silicates. Whole-ore cyanide leaching reached about 94% recovery at roughly 1 kilogram of sodium cyanide per tonne of ore with lime, on head grades of 4.6 to 21.4 grams per tonne of gold. The tests were carried out by the independent laboratory ALS Metallurgy.
The same announcement carries the caveat that matters most for readers: these are indicative laboratory-derived results and do not represent plant-scale recovery. A laboratory treats small, carefully prepared samples under controlled conditions. A real plant treats variable ore, at scale, with equipment wear, water quality changes and operator decisions in the mix, and its recovery is usually lower than the laboratory figure. The Mount Hope example is therefore best read as a worked lesson in how a recovery number is assembled, GRG plus leachability plus locked-gold accounting, rather than as a promise of what any plant will achieve. Any recovery figure in a company report deserves the same question: measured how, on what ore, and at what scale?
Why Recovery Is Never 100%: What Drags It Down
Ore type: free-milling vs refractory
The single biggest factor in recovery is the ore itself. Free-milling ores, where the gold is clean, exposed and ready to dissolve, are the easy case: peer-reviewed research reports that high recoveries above 90% can generally be achieved for such ores. Refractory ores, where the gold is encapsulated in sulfide or carbonaceous minerals, are the hard case: the same peer-reviewed literature puts conventional cyanidation recovery for refractory ores in the range of 50% to 80%, and a separate peer-reviewed study of a low-grade refractory ore reports average recovery below 50% for direct cyanidation.
Here the honest picture requires a conflict note. Vendor guides publish much higher tables, for example free-milling 90 to 95%, sulfide-associated 85 to 93%, refractory 80 to 90% and alluvial 85 to 95%. Those vendor figures clash directly with the peer-reviewed ranges for refractory ore, and vendor tables are unreferenced. The two sets of numbers cannot both be right as universal truths, because recovery depends on the ore, the flowsheet and the measurement basis. This article therefore presents them side by side with their sources, and the reader should trust the attributed, peer-reviewed ranges over any single universal table. Pretreatment can close part of the gap: in one peer-reviewed case, roasting a semi-refractory ore at 620 degrees Celsius lifted gold recovery from 75% to 95.84% and cut cyanide consumption to 6.5 kilograms of sodium cyanide per tonne of ore, which shows that refractory does not mean hopeless, only that it needs extra processing.
Liberation and particle size: gold that never gets freed never gets caught
Every recovery stage assumes the gold is available to it. If grinding leaves gold locked inside rock grains, or if the gold is so fine that gravity cannot settle it and flotation cannot float it, that gold passes to the tailings regardless of how well the rest of the plant performs. This is why liberation is both the first stage of the journey and a permanent limit on it: the plant can only recover gold that its grinding has actually freed, and grinding finer has its own costs and limits.
Particle size cuts both ways. Coarse gold is easy for gravity but may not be fully liberated. Very fine gold may be fully liberated but too small for physical separation, leaving leaching as the only route. A plant’s recovery is therefore a compromise across the whole size range of its ore, not a single stage’s performance, and changes in ore hardness or grain size can move the recovery number even when nothing else in the plant has changed.
Preg-robbing carbon and interfering elements
Some ores actively fight back. In carbonaceous ores, naturally occurring carbon in the ore, known as preg-robbing carbon, adsorbs dissolved gold straight out of the leaching solution before the plant’s own carbon can catch it, like a thief intercepting the delivery. Professional literature reports that preg-robbing can cap conventional cyanidation recovery at around 40%, and peer-reviewed work on the Navachab deposit shows that as little as 0.1% carbon in the ore can cause preg-robbing. This is one of the main reasons a carbonaceous ore is classed as refractory.
Other elements interfere in quieter ways. Peer-reviewed research reports that impurity metals such as copper, zinc and nickel increase cyanide consumption and form film layers on the gold surface, reducing leaching efficiency. Clays can also interfere by coating particles and thickening slurries. None of these effects show up in a head grade. They show up in the recovery number, which is exactly why the number exists.
Typical Recovery Ranges by Ore Type
The table below collects the ranges discussed in this article. Every row is attributed to its source type, and the conflict between vendor tables and peer-reviewed research is stated plainly underneath. No row here should be read as a universal figure: recovery always depends on the specific ore, the flowsheet and how it was measured.
| Ore type | Recovery range | Source |
|---|---|---|
| Free-milling ore | Above 90% | Peer-reviewed research (Kantarcı 2026) |
| Refractory ore, conventional cyanidation | 50% to 80% | Peer-reviewed research (Kantarcı 2026) |
| Low-grade refractory ore, direct cyanidation | Below 50% on average | Peer-reviewed study (ResearchGate record) |
| Carbonaceous (preg-robbing) ore, conventional cyanidation | Capped at around 40% | Professional literature; 0.1% carbon figure from Navachab 2018 |
| Sulfide-associated ore (flotation stage) | 85% to 93% (concentrate typically 20 to 40 g/t) | Vendor-stated range, unreferenced |
| Suitable ores, CIL/CIP route | 90% to 95% | Vendor-stated range, unreferenced |
| Low-grade oxide ore, heap leaching | Lower than tank leaching, over longer times (typically 0.5 to 1.5 g/t head grade) | Vendor-stated range, unreferenced |
Conflict note: vendor ore-type tables, which put refractory ore at 80 to 90%, disagree with the peer-reviewed ranges above, which put refractory ore at 50 to 80% for conventional cyanidation and below 50% on average for low-grade refractory direct cyanidation. Until a figure is tied to a specific ore and a named test method, treat it as a claim, not a fact. The Mount Hope testwork example in this article is the model for how such a figure should be presented: method, sample, laboratory, and the lab-versus-plant caveat stated alongside the number.
Key Takeaways
- Gold recovery is the percentage of the gold in the ore that the plant actually captures. The rest reports to the tailings, and that lost share is what the number exists to measure.
- A modern plant recovers gold in stages, liberation, gravity, flotation, leaching, capture and doré production, and each stage catches a different kind of gold.
- Head grade alone does not describe a project. Recovery, ore type and measurement basis must be read alongside it.
- Free-milling ores generally recover above 90% in peer-reviewed research, while refractory ores recover far less by conventional cyanidation, and preg-robbing carbon can cap recovery at around 40%.
- Recovery figures in company reports are usually laboratory testwork, not plant performance. Always ask how the number was measured, on what ore, and at what scale.
- Recovery is never 100%, because some gold stays locked in minerals, some is too fine to catch, and some is intercepted by preg-robbing carbon or interfering elements.
FAQs
What does “gold recovery rate” mean?
It is the percentage of the gold in the ore that the plant captures, with the rest reporting to the tailings. For example, the Mount Hope testwork reported an indicative combined recovery of more than 98% for its Mt Solitary samples, built from 70.4% gravity-recoverable gold plus 94.6% cyanide solubility of the gravity tailings, but that is a laboratory figure, not a plant result.
What is the difference between gold extraction and gold recovery?
Extraction is the process: the stages that treat the ore, from crushing and grinding through leaching and capture to doré. Recovery is the score: the percentage that says how well those stages worked. Extraction describes what the plant does, recovery describes how well it did it.
Why is gold recovery never 100%?
Because some gold never gets liberated from its host rock, some is too fine for physical separation, and some is intercepted by preg-robbing carbon or blocked by interfering elements such as copper and zinc. Every stage has a limit, and the losses add up in the tailings.
Which ore type gives the highest recovery?
Free-milling ore, where the gold is clean and exposed, gives the highest recovery, above 90% according to peer-reviewed research. Refractory ores, where gold is locked in sulfides or carbonaceous minerals, recover far less by conventional cyanidation, in the range of 50% to 80%, and below 50% on average for low-grade refractory ore by direct cyanidation.
How do plants measure their recovery rate?
By assaying the feed, the products and the tailings and reconciling them over time. In a running plant this is routine metallurgical accounting. In a new project it comes from laboratory testwork, such as gravity-recoverable gold tests and diagnostic leaching, which is how the Mount Hope example’s figures were produced.
Can old mine tailings be reprocessed to recover more gold?
Yes, in principle. Tailings still hold the gold the original plant failed to recover, and if that gold is now recoverable, by finer grinding, a different flowsheet or a pretreatment step, and the economics work, reprocessing can be worthwhile. It is a secondary subject, though: the same limits, liberation, mineralogy and interference, decide whether any given tailings deposit is worth retreating.
Sources
- Kantarcı, “Integration of Cyanidation and Roasting Methods for Complex Gold and Silver Ore with Semi-Refractory Behavior”, Minerals 2026, 16, 1005 (peer-reviewed): MDPI PDF
- Mount Hope Mining Limited (ASX: MHM), “Phase 1 Metallurgy Indicates +98% Gold Recovery at Mt Solitary gold prospect”, ASX announcement, 23 July 2026: ASX announcement PDF
