Copper — Learn This One and the Rest Are Variations
The oldest, best-documented and most complete supply chain of any EV material — and it runs two entirely different routes depending on whether the ore is a sulfide or an oxide.
Ore to Vehicle · Part 2 — The Metals · Chapter 3 · 21 min read
Part 2 — The Metals
The reference chain
Copper has the oldest and most complete supply chain of any EV material, and it runs two entirely different routes from the same deposit.
Learn this one and the rest are variations. Copper is the best-documented chain in this series, and it is the only one where you can watch a single mine split into two completely different process plants because of what weathering did to the top of the orebody.
0.5 → 99.99 %
In six operations
30–50 %
Of mine electricity spent on grinding
~500 t
Rock per tonne of metal
$0
The 2026 TC/RC benchmark
3.1 — The geology decides the chemistry
Most copper comes from porphyry deposits — enormous, low-grade bodies formed where a cooling magma body drove metal-bearing fluids through fractured rock. The Andes are full of them, which is why Chile and Peru dominate.
Near the surface, weathering has oxidised the copper minerals to things like malachite and chrysocolla. Deeper down, the copper is still locked in sulfides, mainly chalcopyrite, CuFeS₂. Oxide ore goes to acid leaching; sulfide ore goes to flotation and smelting. Same mine, two plants.
3.2 — Route A — sulfide: crush, float, smelt, refine
- •1 · Comminution. Ore crushed and ground to roughly 100 µm — a single step that consumes 30 to 50 per cent of the whole mine’s electricity.
- •2 · Froth flotation — physical, not chemical. A xanthate collector makes sulfide surfaces hydrophobic and air bubbles carry them up as froth. 0.5 % Cu ore becomes 25–30 % Cu concentrate at about 88 % recovery.
- •3 · Smelting — flash furnace at ~1,250 °C. 2 CuFeS₂ + O₂ → Cu₂S + 2 FeS + SO₂, with iron leaving as silicate slag. Product is matte at 60–70 % Cu; the SO₂ goes to a sulfuric acid plant.
- •4 · Converting. Cu₂S + O₂ → 2 Cu + SO₂, giving blister copper at 98–99 %. The name is literal: escaping SO₂ blisters the surface.
- •5 · Fire refining. Oxidise remaining sulfur, then reduce excess oxygen with natural gas → anode copper at 99.5 %, cast into 300–400 kg plates.
- •6 · Electrorefining — the purity step. Anode: Cu → Cu²⁺ + 2e⁻. Cathode: Cu²⁺ + 2e⁻ → Cu. In CuSO₄/H₂SO₄ at ~0.3 V over 7–14 days → cathode at 99.99 %, LME Grade A.
3.3 — Where the world’s silver appears
Important
Step 6 is where silver, gold and platinum-group metals appear. They will not dissolve at copper’s anode potential, so they fall to the bottom of the cell as anode slime — a few kilograms per tonne of copper, containing Ag, Au, Pt, Pd, Se and Te.
That slime is the single largest source of silver on earth, and it is the subject of the next chapter.
3.4 — Route B — oxide: leach, extract, electrowin
- •1 · Heap leach. Dilute H₂SO₄ sprayed over stacked ore for months. CuO + H₂SO₄ → CuSO₄ + H₂O, giving a pregnant leach solution at only 1–5 g/L Cu.
- •2 · Solvent extraction. An organic extractant selectively grabs Cu²⁺ from the aqueous phase, then releases it into a clean, strong acid strip solution — a purification and concentration step, from 3 g/L to about 45.
- •3 · Electrowinning. Cathode: Cu²⁺ + 2e⁻ → Cu. Anode: 2 H₂O → O₂ + 4 H⁺ + 4e⁻. About 2 V — six times electrorefining, because water is being split → cathode at 99.99 %.
SX-EW skips smelting entirely, which means no sulfuric acid byproduct, no SO₂ to capture — and no precious-metal recovery, because there is no anode slime. It accounts for roughly a fifth of world copper.
3.5 — What one tonne of copper costs in rock
0.6 % ore grade · 2.5 : 1 strip ratio · 88 % flotation recovery · 98 % smelter recovery
→ roughly 500 tonnes of material moved per tonne of refined copper
Falling grades are the reason this number has been rising for a century, and the reason copper’s energy intensity rises even as smelters get more efficient.
3.6 — The commercial layer, and a genuinely strange market
A mine sells concentrate, not copper. Payment = (payable Cu × LME price) − TC − RC − penalties − freight. Payability is about 96.5 per cent of contained copper — the smelter keeps the rest as its own margin. TC is a treatment charge per dry metric tonne of concentrate; RC is a refining charge per pound of payable copper; penalties apply for arsenic, bismuth, lead and fluorine above thresholds.
3.6.1 — The 2026 benchmark settled at zero
Technical framing
TC/RCs are set each November between one big miner and one big Chinese smelter, and that number becomes the global reference. Historically it ran $80–120/dmt.
The 2026 benchmark settled at $0 per tonne and 0 cents per pound — the lowest ever, after 2025 settled near $20 and 2024 near $80. Spot TCs have been running at or below zero, which means smelters are paying miners for the privilege of processing their concentrate.
Why this matters
The cause is a straightforward imbalance: smelting capacity, mostly built in China, has outrun concentrate supply. Smelters stay alive on byproduct acid and gold, and on cathode premiums that have run past $300/t.
It is a warning about what happens when one stage of a chain is overbuilt relative to the one before it — and worth holding in mind when reading about cell or cathode capacity announcements.
Roughly 23 Mt of copper is mined a year and about 27 Mt refined, the difference being scrap. Chile, Peru and the DRC lead mining; China refines close to half the world’s copper — the mining/midstream split in its clearest form.
Quick check: test yourself
1.Why does SX-EW copper cost the industry its precious metals?
Show answer
2.A smelter agrees a treatment charge of zero. Why would it do that?
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3.Which single step dominates a copper mine’s energy bill?
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Chapter summary
- ✓Weathering splits a porphyry deposit into two chains: oxide ore to heap leach and SX-EW, sulfide ore to flotation, smelting and electrorefining.
- ✓Grinding alone takes 30 to 50 per cent of a mine’s electricity, and it worsens as grades fall.
- ✓Electrorefining is where the world’s silver comes from, as anode slime — which SX-EW forgoes entirely.
- ✓About 500 tonnes of material moves per tonne of refined copper, a number that has risen for a century as grades decline.
- ✓The 2026 TC/RC benchmark settled at zero, meaning smelters now effectively pay for concentrate — a case study in overbuilding one stage relative to the one before it.
Frequently asked questions
Why does a copper mine have two different plants?+
Because the geology changes with depth. Near the surface, weathering has oxidised copper minerals to things like malachite and chrysocolla, which go to acid heap leaching followed by solvent extraction and electrowinning. Deeper down the copper is still locked in sulfides, mainly chalcopyrite CuFeS₂, which go to flotation and smelting. Same deposit, two entirely different process routes.
Where does the world’s silver actually come from?+
Largely from copper electrorefining. Silver, gold and platinum-group metals will not dissolve at copper’s anode potential, so they fall to the bottom of the cell as anode slime — a few kilograms per tonne of copper containing Ag, Au, Pt, Pd, Se and Te. Note that the SX-EW route skips smelting entirely and therefore produces no anode slime and no precious-metal recovery at all.
What does it mean that the 2026 TC/RC benchmark settled at zero?+
Treatment and refining charges are what a smelter deducts from the copper price when buying concentrate, historically 80 to 120 dollars per dry metric tonne. The 2026 benchmark settled at zero dollars per tonne and zero cents per pound — the lowest ever, after 2025 near 20 and 2024 near 80 — and spot has run at or below zero, meaning smelters are effectively paying miners for the privilege of processing their concentrate. The cause is that smelting capacity, mostly built in China, has outrun concentrate supply. It is a warning about what happens when one stage of a chain is overbuilt relative to the one before it.
Why does one tonne of copper require moving 500 tonnes of rock?+
Multiply the losses. At about 0.6 per cent ore grade and a 2.5:1 strip ratio, you move roughly 500 tonnes of material to mill 167 tonnes of ore, which floats to about 3.4 tonnes of concentrate at 88 per cent recovery, smelts to 1.5 tonnes of matte, converts to 1.02 tonnes of blister and refines to one tonne of cathode. Falling grades are why this figure has risen for a century and why copper’s energy intensity rises even as smelters get more efficient.
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Ore to Vehicle is an original educational series on the battery and EV materials supply chain. Country shares, grades, prices and policy status are approximate, drawn from public reporting as of mid-2026, and move year to year — treat them as orders of magnitude rather than as a ledger, and verify before relying on them commercially.