Copper and Selenium

More than 80% of selenium comes from the anode slimes left by electrolytic copper refining, so selenium supply is fixed by copper refinery output, not by selenium demand.

Copper (commodity) and Selenium (commodity): 2 relationships.

How they are linked

1. Recovered from anode slimes

Joint production · Asymmetric · Copper refining yields selenium

Selenium in copper concentrate collects in the slimes at the bottom of electrorefining tanks, from which refiners recover it alongside precious metals. Selenium is worth far too little to justify mining on its own.

• more than 80% of selenium produced from copper anode slimes

The tie runs one way: copper refiners do not change output for selenium, while selenium supply falls when cathode output falls. US output of selenium-bearing anode slimes fell in 2025 because US refineries made less copper cathode, and selenium is no longer refined in the US. Copper made by leaching and electrowinning bypasses electrorefining and leaves no anode slimes, so growth in that route adds copper without selenium.

Sources: US Geological Survey; US Geological Survey

2. Refining concentrated in China

Geography and ownership · Strong · Selenium follows copper refining capacity

Selenium is produced where copper is electrorefined, and China now refines the largest share of the world's copper.

• 12,400 kt China's refined copper output, 2024, about 45% of the world
• 1,800 t China's refined selenium output, 2024, the largest
• 730 t Japan's refined selenium output, 2024, the second largest

As Chinese smelters and refineries have expanded on imported concentrate, selenium output has moved with them. Japan, which refined 1,570 kt of copper in 2024, is the second largest selenium producer. Selenium demand, led by metallurgy including electrolytic manganese (about 40% of world use in 2025), is unconnected to copper, so prices swing when the two diverge.

Sources: US Geological Survey; US Geological Survey

For investors

Key learnings

1. Selenium supply depends on copper cathode output from electrorefineries, so a copper refinery outage is a selenium supply shock.
2. Rising copper output from leaching and electrowinning adds copper without adding selenium.
3. China's dominance of copper refining gives it the largest share of selenium supply as well.

What to track

• Refined copper output by country: Sets the ceiling on selenium supply (Monthly · ICSG, national statistics)
• Selenium price, US and Europe: Shows whether by-product supply is keeping up with demand (about $28 to $29 per kg in 2025) (Monthly · Fastmarkets, Argus)

For policymakers

Key learnings

1. India's selenium output is set by its copper refineries, so expanding domestic copper refining also expands selenium supply.
2. Selenium supply cannot be raised quickly by price, so users such as glass and manganese plants face supply risk tied to copper refinery operations.
3. Encouraging full recovery of selenium and other by-products from anode slimes at domestic refineries adds supply without any new mining.

What to track

• India refined copper output: Indicates domestic selenium potential (Monthly · Ministry of Mines, company reports)
• China selenium export volumes: Shows availability for importing countries (Monthly · China Customs)

India

India refined about 88 t of selenium in 2024 from its copper refineries, which produced 545 kt of refined copper that year.

Sources

1. Mineral Commodity Summaries 2026: Selenium, US Geological Survey (2026)
2. Mineral Commodity Summaries 2026: Copper, US Geological Survey (2026)