Porphyry Copper Ore Grade: Chile vs Japan, by Mine

The median ore grade of a porphyry copper deposit is 0.44% copper, based on 422 deposits compiled by the U.S. Geological Survey (USGS). That is 4.4 kilograms of copper in every tonne of rock. The big Chilean operations report reserve grades between 0.30% and 0.84% in their latest filings, and Japan, often set against Chile, has no discovered porphyry copper deposit, according to a 2014 USGS assessment.

This guide puts the grades side by side, mine by mine, using the operators’ own reserve tables. It explains why Escondida’s plant is being fed richer ore than its reserve average, why Japan is not on the map, how grade turns into money, and what to check when someone quotes you a grade. Grades are in percent copper (% Cu) unless stated. One percent is 10 kilograms per tonne, or about 20 pounds per short ton.

What is a normal porphyry copper ore grade?

A porphyry copper deposit is a large body of rock in which copper minerals are spread thinly through, and around, a buried igneous intrusion. The USGS describes them as more than 100 million tonnes of low to moderate grade ore, usually 0.3% to 2.0% copper, and credits this deposit type with more than 60% of world copper production. Low grade works because the rock is huge and can be dug cheaply in bulk. For a geology primer, see our guide to alteration, grades and discovery in porphyry systems.

Four grade terms matter when you compare mines:

• Ore grade is the share of copper in the rock, in % Cu. Gold and silver are quoted in grams per tonne (g/t).
• Head grade (or feed grade) is the grade of the ore actually going into the mill in a given period.
• Reserve grade is the average grade of the ore a company can mine at a profit under its plan. A resource is a wider estimate that does not yet pass that test, so never mix the two.
• Cut-off grade is the lowest grade that still pays for mining and processing. Below it, rock is waste or stockpile. BHP’s published cut-offs at Escondida are 0.30% Cu or more for sulphide ore sent to the concentrator and 0.25% or more for sulphide leach ore, with variations by processing route.

Two points stand out. First, the Resolution deposit in Arizona averages 1.54% Cu, about 31 pounds of copper per short ton, and BHP’s June 2026 statement reports a 1.86 billion tonne resource at 1.52% Cu, so it is far richer than the global median. The project’s final environmental impact statement still calls it a porphyry deposit that needs high mining rates to pay. Second, grade is not the only driver: depth, hardness, water, power and metal price decide whether a given grade is a mine. The USGS adds that the by-products are small per tonne: median molybdenum of 0.013%, silver of 2.0 g/t in the third of deposits that recover it, and gold of 0.21 g/t in the two-thirds that recover it.

Porphyry copper ore grade in Chile, mine by mine

Chile mined 5.51 million tonnes of copper in 2024 (USGS Mineral Commodity Summaries), and Natural Resources Canada puts its 2024 share of world mined output at 23%, using 5.3 million tonnes. The table lists twelve operations from three reporters, taken from their 2025 or 2026 reports. Other Chilean mines, such as Spence (BHP) and El Abra (Freeport), also publish reserves and are not included. The twelve are all seven copper divisions of the state producer Codelco (reserves at 31 December 2025), four operations reported by Antofagasta plc (31 December 2025) and Escondida, reported by BHP (30 June 2026).

Chart

Reserve grade at eight Chilean operations

Kilograms of copper per tonne of ore (1% Cu = 10 kg/t); selected operations

Chart

Bigger reserves, lower grade

Eight Chilean operations; reserves as reported; 1% Cu = 20 lb per short ton

How we chose and read these numbers. The metric is the reserve grade as each company reports it (proved plus probable where the company splits them), never a resource. Codelco’s reserve table gives 6,809 million tonnes at 0.62% across all divisions. Antofagasta’s annual report gives the figures for Los Pelambres, Centinela, Zaldívar and Antucoya. For Escondida, BHP lists 3,090 million tonnes of proved sulphide at 0.60% and 1,400 million tonnes of probable sulphide at 0.54%. The 0.58% in the table is our tonnage-weighted average of those two lines. Escondida also reports two leach-route reserves that the table leaves out: sulphide leach (1,170 million tonnes proved at 0.38% and 237 million probable at 0.37%) and Full SaL (146 million proved at 0.83% and 34 million probable at 0.61%). Several of the operations, such as Antucoya, Zaldívar and Gabriela Mistral, are cathode producers that leach lower-grade ore, which pulls their numbers down. Reserve figures include whatever ore types each company reports together, so a mine with a lot of leach ore will show a lower number than one that is mostly sulphide.

Eight of the twelve operations report a reserve grade above the 0.44% global median, and four report less. That is not a like-for-like contest, because the USGS median describes deposits and these are mine reserves under each company’s own cut-off and price assumptions. It does show the range a Chilean mine can sit in.

The scatter chart shows a pattern within this set: the biggest reserves tend to have the lower grades. Escondida, Centinela and Radomiro Tomic hold the most tonnes, and Andina and El Teniente, with under a billion tonnes each, report the richest ore.

▶ Follows copper from the Atacama pits to refined cathode and shows how about 0.9% ore becomes pure metal. · 6:03

Escondida: the grade in the plant versus the grade in the reserve

Escondida is the clearest case of why one “average grade” can mislead. In the year to 30 June 2026 its concentrator was fed ore averaging 0.90% copper, down from 1.02% a year earlier. BHP calls the fall planned. Escondida still made 1,261 thousand tonnes of copper, 3% less than the 1,305 thousand tonnes of the year before, because record throughput and better recovery offset part of the lower grade.

Chart

Escondida: plant feed versus reserve grade

kg of copper per tonne (1% Cu = 10 kg/t); concentrator feed by financial year, reserves at 30 June 2026

The same filing guides to a concentrator feed grade of about 0.70% for the next financial year and to Escondida output of 1,000 to 1,100 thousand tonnes. Yet the proved sulphide reserve at 30 June 2026 averages 0.60%. A mine can send its richest blocks to the mill first and leave poorer ore for later, so the plant’s grade and the reserve’s grade differ in any given year, and BHP guides the plant’s grade down from 0.90% toward the reserve average (about 0.70% next year). When a company quotes “the grade”, ask which one: feed grade for one period, reserve grade for the whole plan, or the grade of a resource.

Japan versus Chile: mine output and metal refining

You may see a Japanese porphyry grade of about 0.4% Cu set against about 0.7% for Chile. No such Japanese figure exists, because the USGS porphyry assessment states that no porphyry copper deposits have been discovered in Japan (or in South Korea or Taiwan). The same report says porphyry systems may exist in Japan but are likely to lie deeper than the 1 kilometre depth used for the assessment. Japan has been well explored for many deposit types, so the gap is not a lack of looking.

Chart

Mine versus refinery copper output, 2025 estimate

Thousand tonnes of copper; selected countries

Japan’s old copper came from other kinds of deposit. The Besshi mine in Ehime Prefecture, which Sumitomo says formed through submarine volcanic activity, ran for 283 years and closed in 1973. The USGS table shows no Japanese mine production in 2024 or 2025, only refining: 1,570 thousand tonnes of refined copper in 2024 and an estimated 1,400 thousand tonnes in 2025. With no mines, that metal has to come from imported concentrate and scrap. Chile, by contrast, mined 5,510 thousand tonnes and refined 1,940 thousand tonnes in 2024 in the same table.

The lesson for grade comparisons: Japan and Chile are not two porphyry districts with different ore. Chile is a mining country, and Japan is a refining country with no mined copper to grade. For copper deposit types beyond porphyry, see our overview of copper deposits, top countries and where to explore.

Why copper ore grades have fallen

The USGS median fell from 0.49% (217 deposits, 2002) to 0.44% (422 deposits, 2008). The USGS says the fall likely reflects several factors: less mining of copper-enriched ore near the surface, more mining of lower-grade ore of both kinds, more low-grade oxide ore that is cheap to leach, and higher copper prices that let companies mine poorer rock. In most if not all deposits, enriched sulfide zones from weathering are richer than the unaltered ore below them (USGS), so when the enriched cap is mined out, the head grade drops.

Chart

Mill feed grade at Freeport’s copper operations

% Cu, annual average, 2021 to 2025

Operating data shows the same drift. Freeport’s U.S. copper mines milled ore at 0.38% copper in 2021 and 0.31% in 2025, and the ore it stacked for leaching fell from 0.29% to 0.21% over the same years. Its South American operations (Cerro Verde in Peru and El Abra in Chile) milled ore at between 0.30% and 0.34% over the same five years. Our longer read on average copper ore grade worldwide covers more countries.

Lower grade has a plain cost. At 0.5% you must move 200 tonnes of ore to hold one tonne of copper, before recovery losses. Freeport reports mill recovery of 83.6% at its U.S. mines and 84.3% in South America for 2025, so a tonne of ore gives up a little under 85% of the copper it holds.

How to turn ore grade into money

Ore grade becomes revenue in four steps: tonnes of ore times grade gives contained copper; recovery gives copper in concentrate or cathode; payable share gives the part you are paid for; price gives the dollars. A cut-off grade works the same way in reverse: it is the grade at which revenue per tonne just equals your cost per tonne.

Use the calculator below with your own numbers. Every default is an example, including the price. For orientation only, the USGS estimates the 2025 annual average London Metal Exchange (LME) grade A cash price at 440 US cents per pound, or US$4.40; check today’s price before you rely on any result.

How to read an ore grade claim

Whether you are screening a licence, reviewing a technical report or comparing listed producers, run each grade claim through the same checks:

1. Which category? Reserve (proven or probable), resource (measured, indicated, inferred) or exploration result. Reserves come with a mine plan and cost assumptions; the others do not.
2. Which cut-off? A lower cut-off adds tonnes and lowers the average grade. Ask for the cut-off, not only the average.
3. Which ore types? Sulphide, oxide and leach ore have different recoveries, so a blended number hides a lot.
4. Which basis and date? Mill feed for one quarter, reserves at a stated date, or a resource model. Companies restate reserves each year.
5. Which unit? % Cu, copper equivalent (which folds in gold and molybdenum) or kg/t. Convert before you compare.
6. Which sample? A median of many deposits, an average of one mine, or the best drill intercept are different things.

What lower grade means for land, water and waste

A lower grade means more rock moved per tonne of copper, so more waste rock and tailings (the finely ground rock left after the copper is taken out) for the same output. That puts weight on mine design and on drainage control. When sulphide minerals in waste rock meet air and water, they can make acid; our guide to acid mine drainage and its impacts explains how that happens and how it is managed. BHP attributes its lower copper guidance for the next financial year mainly to the forecast grade decline at Escondida, which shows how grade and volume trade against each other.

▶ Walks through the seven environmental impacts of mining in plain words. · 2:31

What satellites can and cannot say about grade

Satellites cannot read a copper percentage through rock. They can map surface signs of the hydrothermal alteration that surrounds many porphyry systems, such as clay and iron-oxide zones and structural lines, which helps rank areas before field crews are sent. A grade still has to come from samples, drilling and a lab. Satellite results are exploration targets, not a resource estimate.

Farmonaut applies this approach across 20+ mineral types, copper among them. You supply a KML, KMZ or polygon and the target mineral, and the satellite-based mineral detection report is delivered in 5 to 20 business days, depending on area size and mineral complexity. You can request a quote or contact the team to scope a licence area.

▶ Explains how a satellite map becomes a tonnage and grade estimate, and which inputs are measured and which are assumed. · 2:54

If this topic matters to you, read Desalination Plants for Mining in Chile: Capacity Ranked next.

Frequently asked questions

What is the average ore grade of porphyry copper deposits?

The USGS reports a median of 0.44% copper for 422 deposits in a 2008 compilation, down from 0.49% for 217 deposits in 2002. Individual deposits range from about 0.3% to 2.0% copper.

What is a good ore grade for a porphyry copper mine?

There is no single answer. Chile’s large operations report reserve grades from 0.30% to 0.84%, and many pay because of their size. A richer deposit such as Resolution in Arizona averages 1.54%, but depth and cost matter as much as grade.

What is the ore grade at Escondida?

BHP reports concentrator feed of 0.90% copper for the year to June 2026, 1.02% the year before, and guides to about 0.70% for the next year. Its proved sulphide reserve averages 0.60% and the probable sulphide reserve 0.54%.

Which Chilean operation has the highest reserve grade in this comparison?

Among the twelve operations listed, Andina reports the highest reserve grade at 0.84%, ahead of El Teniente at 0.77% and Ministro Hales at 0.72%. Codelco’s figures are for 31 December 2025.

Does Japan have porphyry copper deposits?

No porphyry copper deposit has been discovered in Japan, according to a 2014 USGS assessment of East and Southeast Asia. The assessment notes that such systems could exist but would likely lie deeper than 1 kilometre.

Does Japan mine copper?

The USGS shows no Japanese copper mine output in 2024 or 2025, and refinery output of 1,570 thousand tonnes in 2024. Besshi, a major historic mine, closed in 1973.

What is the difference between head grade, reserve grade and cut-off grade?

Head grade is the grade of ore fed to the mill in a period. Reserve grade is the average of the ore in a mine plan. Cut-off grade is the minimum grade that covers mining and processing cost; ore below it is not sent to the mill.

Why have porphyry copper grades fallen?

The USGS median fell from 0.49% to 0.44% between its 2002 and 2008 compilations, which it links to less enriched ore, more low-grade ore, more leaching of oxide ore and higher copper prices. Freeport’s U.S. mill feed fell from 0.38% in 2021 to 0.31% in 2025.

How much copper is in a tonne of 0.5% ore?

Five kilograms, or about 10 pounds per short ton, before processing losses. At 85% recovery you would get about 4.25 kilograms.

Are porphyry copper deposits only a source of copper?

No. Molybdenum, gold and silver are common by-products. The USGS gives median by-product grades of 0.013% molybdenum, 0.21 g/t gold and 2.0 g/t silver, where those metals are recovered.

Can satellites measure copper grade?

No. Satellites map alteration and structure at the surface to help pick targets. Grade comes from sampling and drilling, and a resource estimate comes after that.