Every gold extraction process starts with the same reality: gold ores behave differently, and a flowsheet built around one assumption can lose payable metal before the circuit is even commissioned. The three core gold recovery methods—gravity concentration, flotation and cyanidation—are rarely competitors. In most plants they operate as sequential stages, each removing a particular type of gold. Which combination makes sense is a technical decision, not a guess. It comes from ore characterisation, mineralogy and laboratory-scale testwork, then gets verified in continuous pilot runs before capital is committed.
Why testwork comes before equipment selection
Ore testwork is the foundation of any defensible flowsheet. A gold extraction process that works well on one ore can under-recover badly on another, because gold occurrence changes with mineralogy, grain size, liberation and the presence of preg-robbing carbon or cyanicides. Before selecting gravity, flotation or leaching equipment, the ore should be subjected to head assays, Bond work index testing, gravity-recoverable gold testing, flotation kinetics and leach amenability tests. Xinhai's CNAS-accredited laboratory performs around 5,000 element analyses per month and roughly 200 beneficiation tests a year, according to the company's published figures. The output is not a generic flowsheet; it is a set of mass balances and liberation data that determines which circuit makes economic sense. For a closer look at how ore characterisation works, see how to test gold ore before you commit to a plant. Where project financing requires a compliant report, the same data can support studies aligned with JORC or NI 43-101 standards.
Gravity concentration: early recovery of coarse free gold
Gravity concentration is a density-based separation that uses gravity, centrifugal force or fluid resistance to separate gold from lighter gangue. Because gold has a high specific gravity, coarse free gold can often be pulled from the circuit before it is over-ground and lost to slimes. The process is simple, has low operating cost and does not rely on chemical reagents.
Common gravity devices include jigs, shaking tables, spiral chutes and centrifugal concentrators. Selection variables include feed rate, particle size range, pulp density and the gold particle's liberation size. A jig suits coarser feeds; a shaking table provides high upgrade ratios for finer sands; a centrifugal concentrator is used for fine free gold that would be missed by conventional tables. In many hard-rock plants, gravity is installed early in the grinding circuit, not as a standalone final recovery step, so that any free gold is captured before sulphide flotation or leaching. For context on how milling and classification set up gravity recovery, read gold ore milling basics. The gravity equipment alternatives are a practical set of options, and the choice comes from ore testwork, not from a supplier's preference.
Flotation: concentrating sulphide-hosted gold
Flotation is a physicochemical separation that uses reagents to render gold-bearing sulphide minerals hydrophobic, so they attach to air bubbles and report to a froth phase. It is the standard route for gold locked in pyrite, arsenopyrite or other sulphide minerals, and it can produce a small, high-grade concentrate for smelting or downstream oxidation.
The key equipment is the flotation cell. Xinhai's installed range includes flotation cells up to 320 m³ per unit, which allows a compact line to handle large tonnages. Reagent selection, pulp pH, aeration and residence time are process variables that control grade and recovery. A rougher-scavenger-cleaner arrangement is common: rougher cells recover most of the gold-bearing sulphides, scavenger cells pull remaining values, and cleaner cells upgrade the rougher concentrate. This is a capital-efficient route when the ore has a meaningful sulphide content. If your deposit is mainly free gold, flotation may be unnecessary or limited to a cleaner stage. See the dedicated gold flotation plant solution for circuit layout details.
Cyanidation (CIL/CIP): dissolving fine gold
Cyanidation is a hydrometallurgical process in which dilute cyanide solution dissolves fine gold and silver, then activated carbon adsorbs the gold-cyanide complex from the pregnant solution. CIL and CIP differ mainly in whether leaching and adsorption happen simultaneously in the same tanks, or sequentially in separate tanks. On suitable ores, recovery can reach 99%. It is not a promise for every ore; preg-robbing carbon, cyanicides and coarse gold will all reduce performance unless the flowsheet is adjusted.
Leaching tanks up to 20 m × 20 m are within the equipment range Xinhai supplies, and they are typically arranged in trains of five to ten stages to keep residence time high enough for dissolution. The process requires rigorous safety and environmental controls. Cyanide is toxic, and its transport, storage and use are governed by compliance procedures and site-specific operating discipline. The International Cyanide Management Code provides a voluntary framework covering production, transport, storage and use. For the process distinction, see CIL vs CIP: how the two carbon circuits differ. The decision to leach, and whether to leach whole ore or a flotation concentrate, comes from testwork on the specific ore.
Liberation is the hidden variable in every gold extraction process
Gold recovery methods only work on gold that has been liberated from gangue. If a gold particle remains locked inside a sulphide or silicate grain, gravity cannot separate it, flotation can only recover the host mineral, and cyanide cannot reach the surface of the gold. The milling circuit therefore sets the upper limit for downstream recovery. A common mill product target for leaching or flotation feed is a P80 of 75 µm, which means 80% of the sample passes a 75 µm screen. Finer grinds increase liberation but also increase power consumption, reagent consumption and fine slimes that can hurt flotation or leaching.
Classification devices, especially hydrocyclones, control this grind size. Key variables include cut size, feed pressure, pulp density and overflow fineness. If the cyclone is returning too much coarse material to the mill, the circuit may over-grind and create slimes. If it is passing too much coarse material, gold remains locked and recovery falls. The same logic applies to screens and gravity devices within the grinding circuit. For a closer look at the milling side, see ball milling for gold processing. This is why a recovery flowsheet and a milling flowsheet are not designed separately; they are two halves of one mass balance.
Combining routes in a practical flowsheet
Most operating gold plants use more than one recovery method. A common arrangement is gravity concentration in the grinding circuit to capture coarse free gold, followed by flotation to produce a sulphide concentrate, and then cyanidation of that concentrate or the flotation tailings. This is a recovery cascade, not a single choice. Another route uses heap leaching for low-grade, large-tonnage deposits where a conventional milling and agitation leach circuit would be too capital intensive. Heap leaching can be slower and weather-dependent, but it is a legitimate option for oxide or weakly mineralised ore. See heap leaching gold processing for the trade-offs.
One practical targeting principle: recover free gold as early and as coarse as possible, recover sulphide-hosted gold by flotation, and dissolve remaining fine gold by cyanidation. Each stage reduces the load on the next stage and protects overall recovery. For a plant treating 1,200 t/d of mixed oxide-sulphide ore, a credible baseline could be gravity-plus-flotation-plus-leach, but the actual mass split and reagent regimes depend entirely on the test results. No credible engineer would copy that number into a feasibility study without laboratory confirmation.
| Ore character | Primary method | Common add-on |
|---|---|---|
| Coarse free gold in alluvial or hard rock | Gravity | Flotation or leaching for fines |
| Gold in sulphide minerals | Flotation | Concentrate regrind and leaching |
| Fine gold in oxide ore | CIL/CIP | Gravity scalping before grind |
| Low-grade oxide or heap leachable | Heap leaching | Agglomeration or cement addition |
How Xinhai turns testwork into a gold recovery plant
Xinhai reports having served more than 2,500 mines and delivered over 600 Mine EPC+M+O projects in more than 100 countries. The group's gold recovery capability covers gravity, flotation, CIP/CIL cyanidation and heap leaching, and its three intelligent manufacturing bases cover roughly 110,000 m². Large equipment includes ball mills up to 7 m in diameter, flotation cells of 320 m³, leaching tanks of 20 m × 20 m and thickeners up to 100 m in diameter. Those numbers come from the company's published figures, not from an independent audit.
Design work is supported by a CNAS-accredited laboratory and an industrial-grade pilot base. The design institute holds a Class B metallurgical qualification in China, and design documents can be prepared to JORC or NI 43-101 standards where project financing requires it. A metallurgical flowsheet built on laboratory data—not guesswork—is what protects your recovery and your budget. If you need a recovery route recommendation for your ore, talk to an engineer or review the gold milling plant solution.