Gravity Separation of Copper Ore: Methods, Limits, Steps

Gravity separation works on copper ore only when the copper minerals are much denser than the waste rock and are freed from it at a coarse enough size. That fits native copper, cuprite and some coarse sulfides. It fits fine-grained chalcopyrite, and clay-rich oxide ores, poorly, so most copper mines run froth flotation and use gravity for pre-concentration or as a side circuit. A U.S. EPA process description says copper ores contain less than 1 percent copper and are upgraded by crushing, grinding and flotation into concentrates of 15 to 35 percent copper (an older description, based on data from the 1990s) (EPA AP-42, section 12.3).

This guide shows how to judge whether your ore suits a jig, spiral, shaking table, centrifugal concentrator or dense media plant, how to run a seven-step bench test, and what published test data say about recovery. It also folds in the pros and cons that readers usually search for. The calculator near the end turns your own feed grade, concentrate grade and recovery into the share of rock you can throw away. Each figure below names its source; mineral copper shares and the criterion of concentration are our own calculations.

Does gravity separation work on copper ore?

Sometimes. Gravity methods sort particles by density, so they need two things: a clear density gap and particles that are liberated, meaning each grain is mostly one mineral. The Heliyon review of gravity concentration notes that conventional equipment struggles with fine and ultrafine particles, and that flotation took over for fine material in many circuits (Nzeh et al., Heliyon, 2023). Many copper sulfide ores are disseminated, meaning the copper grains are small and spread through the rock, which is the hard case for gravity.

Gravity is not the main route for copper. World mine output of copper was an estimated 23 million tonnes of contained copper in 2025 (USGS Mineral Commodity Summaries, 2026), and the EPA description above shows flotation as the standard route for turning ore into smelter feed. Gravity has three real jobs in copper: recovering coarse native copper, rejecting waste early, and catching coarse particles before they reach a mill.

Two terms help here. Grade is the share of copper in the rock, in percent. Recovery is the share of the copper in the feed that ends up in the concentrate. A gravity circuit that makes a rich concentrate but leaves half the copper in the tailings has a recovery problem, not a grade problem. If you are still deciding which copper minerals your deposit holds, our guides to copper ore minerals and copper ore types cover the basics.

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Which copper minerals respond to gravity

A quick screen is the criterion of concentration, written CC. It is the density of the heavy mineral minus the density of the water, divided by the density of the light mineral minus the density of the water. The Heliyon review says a value above 2.5 points to easy separation in wet gravity equipment, and that efficiency falls as the value drops. We used each mineral’s measured density from the Mineralogical Society of America’s Handbook of Mineralogy, midpoints where a range is given, quartz at 2.65 as the waste rock, and water at 1.0.

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Denser copper minerals also hold more copper

Density from the Handbook of Mineralogy; copper share calculated from the ideal formula

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Criterion of concentration for copper minerals against quartz

CC = (heavy density – 1) / (quartz 2.65 – 1); above 2.5 means easy separation in water

The result sorts copper minerals into three groups. Native copper (8.95 g/cm³), cuprite (6.14) and chalcocite (5.5 to 5.8) score above 2.5 and are good candidates. Bornite (5.06 to 5.08) is on the line. Chalcopyrite, the most common copper sulfide, scores about 1.9, and malachite about 1.85. Chrysocolla, a common oxide, has a measured density of 1.93 to 2.4, lighter than quartz, so density cannot concentrate it at all.

Sources for the densities: chalcopyrite, bornite, chalcocite, covellite, malachite, cuprite, native copper, quartz and chrysocolla.

The copper percentages are calculated from the chemical formulas, not taken from a lab. Real grains carry impurities, so treat them as upper bounds. The scatter chart shows the trade-off: dense minerals tend to hold more copper per grain, which is why a heavy, coarse particle is both easy to catch and valuable. Pyrite, which is common in copper deposits, has a measured density of about 5.02 (Handbook of Mineralogy), close to bornite, so it can follow copper minerals into a gravity concentrate and has to be removed later.

Gravity methods for copper ore compared

Each device suits a size range and a job. The table uses size limits that the cited reviews give and says so where a limit comes from one study only.

The figures for jigs, spirals, centrifugal units and DMS come from the Heliyon review; the table-size range comes from the study discussed next. The review’s own tests used cassiterite and zircon sands, not copper, so use the ranges as a starting point and let your own bench test decide. Related methods such as magnet-based concentration are covered in our magnetic separation guide, and the sister page on ore gravity separation methods covers the principle across other commodities.

How to test gravity concentration on copper ore in 7 steps

Run this sequence on a core or bulk sample before anyone buys equipment. Each step is a decision, not a formality.

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The 7 test steps in 5 stages

1. 1Identify mineralsFind which copper minerals are present and their grain size.
2. 2Grind and screenCrush to liberation size and split into size fractions.
3. 3Sink-float testWeigh what sinks in heavy liquids of known density.
4. 4Bench testRun table, jig or centrifugal tests and assay all products.
5. 5CompareSet the results beside direct flotation and decide.

1. Identify the copper minerals. Use thin sections or a scanning electron microscope scan. Chalcopyrite, chrysocolla and malachite call for different plans (see the density table above).
2. Find the liberation size. Crushing and grinding break the rock until grains of copper mineral separate from waste. The study cited below found its ore needed a grind to about 74 micrometres (80 percent passing). Grinding finer than needed creates slimes, which gravity devices lose. Our note on rock crushing explains the equipment.
3. Screen into size fractions. Test each fraction separately, because recovery changes sharply with size, as the dumbbell chart shows.
4. Run a sink-float test. Immerse each fraction in heavy liquids of known density and weigh what sinks. This tells you how much waste could be rejected at what copper loss, before you build anything.
5. Bench-test the right device. Use a shaking table or small jig for coarse fractions and a centrifugal unit for finer ones. Record grade and recovery for concentrate, middlings and tailings.
6. Compare with direct flotation. Gravity earns its place only if it beats or helps flotation on the same sample. Run both and compare the grade-recovery curves.
7. Check the tailings. Assay the tailings by size. If most lost copper sits in the finest fraction, gravity is not the right tool for that fraction.

What published test data show

A 2026 study in Scientific Reports tested a low-grade ore (0.5 percent copper) from drill core, made of chalcopyrite and malachite mixed with clay. Shaking-table runs on the minus 120 micrometre fraction gave a concentrate at 6.6 percent copper with 66 percent of the copper recovered. The minus 74 micrometre fraction gave a richer concentrate, 16.2 percent, but only 40.5 percent recovery, and about 54 percent of the copper was lost to tailings. The authors link this to the poor performance of shaking tables on finer particles. Re-floating the table tailings recovered only about 4 percent of the copper at 0.15 percent grade, so the loss was permanent (Sobouti and Rezai, Scientific Reports, 2026). The abstract reports a final two-stage concentrate (table plus flotation) at 27.1 percent copper and 69.94 percent recovery.

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Flotation results with and without pre-concentration

Complex sulfide ore, 0.96% copper feed

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Shaking table on a 0.5% copper ore: grade versus recovery

Concentrate copper grade and copper recovery by feed size

Pre-concentration, meaning rejecting waste before the mill, showed better results on a 0.96 percent copper sulfide ore in one thesis than on the 0.15 to 0.2 percent Mount Polley ores. A master’s thesis on a complex sulfide ore at 0.96 percent copper used heavy medium separation to reject up to 60 percent of the mass at about 84 percent copper recovery, leaving a 2.22 percent copper pre-concentrate. Flotation of that pre-concentrate gave a 27.52 percent copper concentrate at 89.05 percent recovery, against 18.12 percent and 72.63 percent for flotation of the untreated ore (Middle East Technical University thesis).

Not every ore responds. Dense medium tests on four low-grade copper ores from the Mount Polley mine (0.15 to 0.2 percent copper, mostly disseminated chalcopyrite) could not raise the grade and keep acceptable recovery and mass rejection at the same time. Copper followed iron minerals in the sink fraction, so the ore’s mineralogy limited the method (Arinaitwe et al., Canadian Institute of Mining, Metallurgy and Petroleum, 2014). The lesson from all three studies is the same: test your own ore.

Where gravity pays: native copper and coarse sulfides

The Keweenaw Peninsula in Michigan is the classic case. National Park Service teaching material describes how crushed rock was washed and sorted in water at stamp mills, with the heavier copper falling to the bottom of the sorters before it went to the smelter (National Park Service, Keweenaw lesson). Native copper is dense and malleable, so it survives crushing as flakes that settle fast. Michigan is still listed among the U.S. copper-producing states (USGS, 2026).

Today gravity circuits mostly appear as a pre-concentration stage ahead of the mill, as a small circuit to recover coarse native or high-grade copper, or alongside flotation for ores with both coarse and fine copper. For the sulfide minerals involved in those flowsheets, see our overview of copper sulphide ores.

Gravity versus flotation for copper

Readers often ask which is better. The honest answer is that they work on different parts of the size range, and many plants use both. The Scientific Reports paper notes that flotation is the widely used technique for separating valuable minerals from gangue by surface properties, with xanthates the most common collectors for copper sulfides, while oxide ores usually need an extra sulfidation step. It also shows the limit of flotation: clay, iron oxides and very fine particles hurt sulfidation flotation, which is the reason the authors added a gravity stage.

Pros and cons of gravity concentration for copper

Advantages. It uses water and density rather than reagents, so it avoids collectors and frothers (the Heliyon review and the Scientific Reports paper both note this). It can reject waste before grinding, which cuts mill load, as the thesis results show. The equipment is mechanically simple and the process is easy to watch, so problems show up quickly.

Limits. It needs a density gap and liberation. It loses fines: in the shaking-table data, recovery fell from 66 to 40.5 percent as the feed got finer. It does not work on low-density oxides such as chrysocolla. It cannot reach the 15 to 35 percent concentrate grade smelters expect from most ores unless the copper is coarse or the stream is cleaned by flotation afterwards. Cost depends on the ore, the water supply and the mill the gravity stage replaces.

Estimate how much rock a gravity stage can reject

The calculator below applies a simple mass balance. Enter your feed grade, the concentrate grade your bench test produced and the copper recovery. It returns the concentrate tonnage, the share of feed rejected, the tailings grade and the value of payable copper in the concentrate at a price you choose.

Worked example using the thesis numbers: a feed of 0.96 percent copper, a pre-concentrate of 2.22 percent and a recovery of 84 percent gives an enrichment ratio of 2.3, a rejection of about 64 percent of the mass and tailings near 0.24 percent copper. The thesis reports rejection of up to 60 percent at the same recovery, so the mass balance gives a slightly higher rejection than the lab figure, which is expected because the thesis states a maximum. If your rejection figure from the calculator is far above what a sink-float test supports, your recovery or concentrate grade is probably too optimistic.

Read the tailings grade as a warning light. A tailings grade that is higher than your plant’s cut-off for waste rock means the gravity stage is throwing away ore, and the value line in the calculator shows what the payable copper in the concentrate is worth so you can weigh that loss against the milling saved. Prices are inputs: use today’s price from the LME or COMEX, and remember that smelter terms, treatment charges and freight reduce what a mine actually receives.

Water and tailings

A gravity circuit uses water to carry particles, and jigs in particular use a lot of it, which the Heliyon review lists as a demerit. Plan for recycling and for storing the tailings, which still hold the copper that escaped. Gravity tailings contain no flotation reagents, but they are still crushed rock that needs engineered storage and monitoring. Satellite imagery can help with the monitoring side by tracking vegetation, water bodies and surface change around a site over time.

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Before you build a plant: know the ore and the ground

Metallurgical test work starts with a sample taken from the right place. Satellite spectral data cannot measure grain size or density, but it can map surface alteration and help choose where to drill and sample. Farmonaut screens a licence area from satellite data and returns exploration targets, which sit ahead of any resource estimate and any metallurgical test.

▶ Step-by-step tutorial on mapping a mining concession from satellite data. · 6:03

For a closer look at a related question, see our guide: Blast Vibration Monitoring in Mining: Limits and Steps.

If this topic matters to you, read Thoriated Tungsten: Safety, Color Codes, Alternatives next.

Frequently asked questions

Is gravity separation used for copper ore?

Yes, but mainly for native copper, coarse high-grade ore and pre-concentration. Most copper sulfide ore goes to flotation, which the EPA describes as the way mine-site concentrates reach 15 to 35 percent copper.

What is the best gravity method for copper?

It depends on particle size. Jigs and dense media suit coarse rock, shaking tables suit sand-sized grains, and centrifugal concentrators are used for finer material. A bench test on your ore settles it.

What is the specific gravity of copper?

Native copper has a measured density of 8.95 g/cm³ (Handbook of Mineralogy). Copper minerals are lighter: chalcopyrite is 4.1 to 4.3 and malachite about 4.05.

Why does chalcopyrite respond poorly to gravity?

Its density of 4.1 to 4.3 is only about 1.6 times that of quartz, and it usually occurs as fine grains locked in rock. Its criterion of concentration is about 1.9, under the 2.5 benchmark.

How is copper separated from its ore?

Ore is crushed and ground, then concentrated by flotation, and the concentrate is smelted. Gravity steps can be added before or beside flotation.

Does gravity concentration use chemicals?

The concentration step itself relies on water and density, so it needs no flotation reagents. Heavy media plants add a dense suspension that is recycled.

What particle size is best?

Conventional devices lose efficiency on fines. In one study the table recovered 66 percent of the copper from the minus 120 micrometre fraction and 40.5 percent from the minus 74 micrometre fraction.

Can gravity recover copper from tailings?

Only if the copper is coarse and liberated. In the Scientific Reports test, flotation of table tailings recovered about 4 percent, which shows the lost copper was too fine.

Is gravity pre-concentration worth testing?

For coarse, higher-grade sulfides, a thesis reported up to 60 percent of mass rejected at about 84 percent recovery. For low-grade disseminated ore, Mount Polley tests found it did not work. Run a sink-float test first.

Can a small operator use these methods?

Yes, jigs and tables are common at small scale. Use the licence you hold, get permission to work the ground, and do not use mercury to catch fine metal.