Gold and Copper Concentrate: Grades, Payables, Charges

A concentrate is what a mill sends to its next buyer after ore has been crushed, ground and separated. Copper sulfide concentrate carries 25 to 35% copper (USGS Open-File Report 2012-1089) and goes to a smelter, which pays for most of the metal but keeps treatment and refining charges. Gold concentrate is a gravity or flotation product (flotation floats the wanted minerals on air bubbles in a water slurry and skims them off) that is either sold or treated further to make bullion. Diamond “concentrate” is only an intermediate step inside the recovery plant, because only the stones are sold. This page gives the grades, payable terms and smelter charges for each, with dates and sources, plus two calculators.

It is written for consultants and project owners who need to read an offtake term sheet or a feasibility study. Every number carries its source and year. Where a figure comes from one project’s study, it is labelled as an example and not a market rate.

How much ore it takes to make one tonne of concentrate

Concentrating is a ratio. A flotation mill takes ore with a low grade (the share of the target metal in the rock) and produces a smaller stream with a much higher grade. The USGS models a copper plant that treats 17.5 million tonnes (Mt) of ore a year at 0.50% copper with 90% recovery. It makes about 292,000 tonnes of concentrate at 27% copper and leaves 17.2 Mt of tailings, the finely ground waste (USGS, 2012). That is roughly 60 tonnes of ore for every tonne of concentrate, and a concentrate grade 54 times the ore grade.

Gold and diamonds show very different ratios. In a 2025 laboratory study of the Faina deposit in Brazil, ore at 7.8 grams per tonne (g/t) gold produced flotation concentrates of about 22 g/t and 62 g/t gold in two test batches (REM, 2025). That is an upgrade of about 3 to 8 times, because the gold sits inside sulfide grains that carry a lot of other rock. Diamond ore is far leaner still: most diamond ore bodies hold less than 1 carat to about 6 carats per ton of ore (USGS Mineral Commodity Summaries, 2026). A metric carat is 0.2 grams (NIST SP 811), so one carat per tonne is only 0.2 g/t of stones.

The calculator below applies the same mass balance to your own mill. Its starting values are the USGS model. For gold or other trace-grade metals, enter grades in percent (1 g/t is 0.0001%).

Copper concentrate: grade, payable metal and by-product gold

Copper concentrate is made from sulfide ore, mainly chalcopyrite. Pure chalcopyrite holds 35% copper, and waste minerals that are not fully separated dilute the real product (Troilus concentrate marketing study, 2024). The USGS gives a range of 25 to 35% for the concentrate. About 13 Mt of copper, roughly 80% of the world’s primary supply, came from flotation concentrate in 2011, the USGS reports, citing the International Copper Study Group.

Infographic

From ore to refined copper in 4 steps

1. 1Grind and floatOre is crushed and ground, then sulfide minerals are floated into a concentrate.
2. 2Dewater and shipThickeners and filters cut moisture to 8% to 10% before the concentrate is loaded.
3. 3Smelt and refineThe smelter makes copper and recovers gold and silver at the electro-refining stage.
4. 4Settle the invoiceThe miner is paid for payable metal minus treatment charges, refining charges and penalties.

The smelter never pays for 100% of the copper. Contracts use a payable percentage, often with a minimum deduction of one unit (one percentage point of the concentrate’s weight). For concentrates between 20% and 28.57% copper, the one-unit rule is usually used. A 25% concentrate is paid on 96.0% of its copper and a 28.5% concentrate on 96.49% (Troilus study). Hudbay’s 2023 pre-feasibility study for its Copper World project in Arizona assumes 96.5% payable copper with a one-unit minimum deduction, a treatment charge of US$75 per dry metric tonne (dmt), a refining charge of US$0.075 per pound and 8% moisture (Hudbay, 8 September 2023). Those are one company’s modelling inputs, not a market quote.

Gold and silver paid inside copper concentrate

Precious metals in the concentrate are recovered at the electro-refining stage and paid for above a minimum grade. The Troilus study lists typical payment scales that differ by smelter region. Chinese smelters have less experience with gold-bearing feed, and the study says their scales are lower than elsewhere.

Source: Troilus Gold concentrate marketing study, Rev 4, 4 June 2024. The study lists these as typical terms for financial modelling. European smelters in the same table pay 97% to 98% with a gold minimum deduction of 0.7 to 1.0 g/t.

Penalties for unwanted elements

Smelters deduct money when a concentrate carries elements that harm copper quality or raise their handling costs. For arsenic the study gives a typical limit of 0.20% and a deduction of US$2 to US$3 per tonne of concentrate for each 0.1% up to 0.5%, rising to US$5 to US$8 per 0.1% up to 1%. It also describes a Chinese import rule that lets port authorities reject copper concentrate above 0.5% arsenic, 6% lead, 1,000 ppm fluorine, 100 ppm mercury or 500 ppm cadmium. The AusIMM adds that an excess of one contaminant from a large producer can limit how much of that contaminant other sellers can place (AusIMM Bulletin, April 2021).

Treatment and refining charges: what the smelter keeps

A treatment charge (TC) is a fixed fee per dry tonne of concentrate. A refining charge (RC) is a fee per pound of payable copper. Miners pay both to smelters. The charges fall when mine supply is tight, because smelters then accept poorer terms to secure feed. Each year the biggest miners and Chinese smelters agree a benchmark for long-term contracts. Antofagasta and a Chinese smelter agreed terms of US$0 per tonne and 0 cents per pound for 2026, the lowest ever settled in annual talks, against US$21.25 and 2.125 cents for 2025 (Reuters, 19 December 2025, via Mining.com). Shanghai Metals Market reported the same 2026 benchmark as finalised with Chinese smelters on 20 December 2025 (SMM).

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Copper concentrate treatment charge benchmark

US$ per dry tonne, annual benchmark for long-term contracts, 2019 to 2026

Reuters linked the squeeze to outages at the Grasberg mine in Indonesia and the Kamoa-Kakula mine in the Democratic Republic of Congo, which tightened supply so much that spot processing fees turned negative. The 2024 benchmark was US$80 per tonne and 8 cents per pound, 9% below the 2023 level of US$88 and 8.8 cents (Reuters via Mining.com, 18 November 2023). The 2020 treatment charge of US$62 was the fifth straight annual fall, down 23% from US$80.8 in 2019 (SMM, November 2019). Treatment charges were US$59.5 for 2021 and US$65 for 2022 (SMM, December 2021), and US$21.25 for 2025 (SMM, December 2024).

The benchmark is a reference, not a price every seller gets. Producers of all sizes have moved away from it, because concentrate quality differs and spot terms capture swings inside the year; in a deficit spot terms sit below the benchmark and in a surplus above it (AusIMM, 2021). On 1 July 2026 Reuters, relaying a Shanghai Metals Market report, said Antofagasta had agreed to sell term concentrate to some Chinese smelters at spot-indexed charges with a guaranteed floor, a break from fixed benchmark charges. The floor level was not disclosed, Antofagasta said its talks were confidential, and Argus put spot treatment charges near minus US$126.80 per tonne at the end of the previous week (Reuters via Mining.com, 1 July 2026). For a deeper look at how concentrate is priced per tonne, see our guide to copper concentrate price per ton and process.

Where copper concentrate comes from

World copper mine output was an estimated 23 million tonnes of contained copper in 2025, with Chile, the Democratic Republic of Congo and Peru supplying the largest shares (USGS Mineral Commodity Summaries, 2026). The chart shows all mine copper, which is the recoverable copper in all mine output, so it is a ceiling for concentrate and not a count of it.

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World copper mine production, leading countries

Thousand tonnes of contained copper, 2025 estimate, all mine output

The United States has 2 primary smelters and exported an estimated 340,000 tonnes of copper in ore and concentrate in 2025 (USGS, 2026), so smelter terms set abroad affect American mines. For the geology behind these deposits, see copper deposit types and top countries and porphyry copper alteration, grades and discovery.

Gold concentrate: gravity, flotation and the route to bullion

Gravity concentration separates minerals by differences in density (review of heavy-mineral methods in PMC, 2023). Fine gold locked in pyrite or arsenopyrite is floated into a sulfide concentrate. Cyanide leaching alone is not suitable for refractory ores or floated concentrates, so the concentrate needs an oxidation step first. Pressure oxidation has been used since the mid-1980s, and recoveries of 90% to 95% are typical for a wide range of ores and concentrates (REM, 2025). The end product is doré, an unrefined gold and silver alloy poured into bars at the mine and sent to a refinery.

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World gold mine production, selected countries

Tonnes of gold, 2025 estimate

Some gold is not mined as a gold project at all. About 7% of US gold in 2025 was recovered as a by-product of base-metal ores, chiefly copper ores (USGS Mineral Commodity Summaries, 2026). The same USGS summary puts world mine production at an estimated 3,300 tonnes in 2025 and the US annual average price at US$3,300 per troy ounce. For trade, the Troilus study says Chinese import rules were due to change in the second half of 2021 to treat material above 15 g/t gold as gold concentrate, with an arsenic cap of 3.5% for 15 to 60 g/t gold and 6.5% above 60 g/t.

▶ A claymation walk through how gold is mined and refined, from rock to ring. · 5:27

Diamond concentrate: why only the stones are sold

A diamond plant makes a heavy-mineral concentrate and then removes the stones from it. Modular recovery plants crush, scrub and screen the feed, run dense media separation (DMS) to float away light rock, and finish with grease and X-ray sorting modules (SGS diamond recovery brochure). The concentrate stays in the plant. The product that leaves is rough diamond, which the Kimberley Process records by weight and value.

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Rough diamond production by country

Million carats, 2025, leading eight producers

The Kimberley Process reports 98.8 million carats of rough diamonds produced worldwide in 2025, valued at US$9.23 billion, an average of US$93.43 per carat (Kimberley Process, Annual Global Summary 2025). Russia produced 31.5 million carats, about 32% of the total. Value per carat varies widely: US$24.33 in Zimbabwe, US$63.28 in Canada and US$343.88 in Namibia. The USGS describes a global natural diamond market that has been in a downturn since early 2023, with lower rough prices that affect the ability of mining companies to keep operations running (USGS, 2026).

Gold, copper and diamond concentrate compared

Source: USGS Open-File Report 2012-1089 and Mineral Commodity Summaries 2026; REM 2025; Troilus Gold concentrate marketing study 2024; SGS recovery brochure.

Water, tailings and the footprint of a concentrator

A conventional copper flotation circuit needs roughly 1.5 to 3.5 tonnes of water for each tonne of ore. In the USGS model at 2.5 tonnes per tonne, a plant treating 17.5 Mt of ore uses about 44 Mt of process water a year. About 17 Mt of that goes to the tailings facility as slurry, and about 11 Mt of it is lost to entrainment, evaporation and seepage. Over 20 years, only about 35% of the water the plant needs would come from the tailings facility, and 65% would have to be sourced elsewhere (USGS, 2012). The concentrate itself leaves with 8% to 10% moisture, which is under 1% of the plant’s estimated water losses (USGS, 2012). Recycling rates differ plant by plant, so a generic recycling percentage is not a reliable benchmark.

The tailings are the larger footprint: 17.2 Mt a year in the model, far more than the concentrate that is shipped. Dewatering, thickening and tailings storage design therefore sit at the centre of any permit review.

▶ A plain-language claymation on the seven environmental impacts of mining. · 2:31

Checklist before you buy or sell a concentrate

1. Get an independent assay of the metals and of the penalty elements (arsenic, antimony, bismuth, mercury, fluorine, chlorine).
2. Check the copper grade against the one-unit rule: below about 28.57% copper the payable share falls under 96.5%.
3. Model each payable metal with its minimum grade, such as gold paid only above 1 g/t in the Copper World example.
4. Compare treatment and refining offers from smelters and traders. Traders blend material and may account for about 45% of the custom and traded market, according to the AusIMM article (2021).
5. Add freight, moisture and the pricing month, called the quotational period.
6. Check the import limits of the destination country before you agree the contract.

Where satellite data fits before a concentrate exists

Before a mill can make a concentrate, someone has to find the ore. Farmonaut’s satellite-based mineral detection screens a licence area for gold, copper and diamond targets from space, with reports delivered in 5 to 20 business days. The results are exploration targets that sit ahead of any resource estimate. Grade, recovery and concentrate quality are shown only by drilling, assays and metallurgical tests. To scope an area, use the mining query form or contact us.

▶ A short look at the Farmonaut Mining Pro platform for screening a licence area. · 4:56

Frequently asked questions

What is a copper concentrate?

It is the product of a flotation mill that treats sulfide ore. It contains 25% to 35% copper and is shipped to a smelter (USGS, 2012).

Why does the smelter pay for less than all the copper?

Contracts pay a share of the copper, commonly 96.5% with a minimum deduction of one unit. In the Troilus study a 25% concentrate is paid on 96.0% of its copper.

What are treatment and refining charges?

A treatment charge is a fee per dry tonne of concentrate. A refining charge is a fee per pound of payable copper. Both are paid by the miner to the smelter.

What did the newest annual copper treatment charge benchmark settle at?

For 2026, Antofagasta and a Chinese smelter agreed US$0 per tonne and 0 cents per pound in December 2025, the lowest ever settled in annual talks (Reuters via Mining.com).

What is a gold concentrate?

It is a gravity or flotation product with far more gold per tonne than the ore. In one Brazilian test the ore held 7.8 g/t and the concentrates 22 and 62 g/t (REM, 2025).

How much gold does a smelter pay for in copper concentrate?

Nothing below 1 g/t. At 1 to 3 g/t the typical scale is 90%, rising to 97% to 98.2% above 50 g/t depending on region (Troilus study, 2024).

Is there such a thing as diamond concentrate?

There is a heavy-mineral concentrate inside the plant, but the product sold is rough diamond, counted in carats by the Kimberley Process.

How much ore is needed to make one tonne of concentrate?

In the USGS model of a 0.50% copper ore, about 60 tonnes of ore per tonne of 27% concentrate.

Which country mines the most rough diamonds?

Russia, with 31.5 million carats in 2025 or about 32% of the Kimberley Process total.

Can satellite imagery show what concentrate a deposit will make?

No. Satellites flag alteration and mineral targets for exploration. Concentrate grade and quality come from assays and metallurgical test work.