Rhodium + Iridium — combined dossier

Covered together as the two critical minor platinum-group metals. Their economics are inseparable from platinum: both are fixed-ratio by-products of PGM mining (no rhodium mine or iridium mine exists anywhere on Earth), so their supply cannot respond to their own prices — only to platinum-mine economics.

Added 2026-07-13 under the all-chokepoints rule: this platform scores every material with high global-supply-chain impact and a concentrated chokepoint, wherever that chokepoint sits. For the minor PGMs it sits in South Africa (~83% of supply from the Bushveld Igneous Complex), not China — the sharpest non-Chinese concentration in our register.

What they are

Rhodium (Rh): atomic number 45, the highest-priced metal commonly traded — it peaked near $29,000/troy oz (~$930,000/kg) in 2021. ~85-90% of demand is automotive catalysts, where rhodium is the only effective NOx-reduction metal. Tightening emissions rules (Euro 7, China 6) are the structural demand driver; there is no drop-in substitute at current loadings.

Iridium (Ir): atomic number 77, one of the rarest stable elements in Earth's crust (~7-8 t mined per year, worldwide). The critical use is the oxygen-evolution anode coating in PEM electrolysers — the electrolyser architecture best suited to intermittent renewable power. Every serious green-hydrogen scenario collides with the same wall: multi-GW electrolyser buildouts require iridium loadings that, at today's ~8 t/yr, supply cannot deliver. Other uses: spark-plug tips, crucibles for growing sapphire and semiconductor crystals, OLED materials, deep-sea/space electronics.

The chokepoint — and why it can't be mined away

• **~83% of both metals comes from South Africa's Bushveld

complex** (Anglo American Platinum, Impala, Sibanye-Stillwater, Northam). The UG2 reef is relatively rich in minor PGMs; Russia's Norilsk ore, the world's #2 PGM source, is palladium-rich but minor-PGM-poor — so Russia cannot backfill a South African disruption of Rh/Ir specifically.

• By-product trap: Rh and Ir emerge in a roughly fixed ratio

to platinum. If iridium demand triples, nobody can "open an iridium mine" — supply only grows if someone mines more platinum at platinum prices. High Rh/Ir prices therefore do NOT call forth new supply the way they would for a primary metal. Recycling (autocatalyst scrap for Rh) is the only elastic lever.

• Single-grid risk: the entire chokepoint runs on Eskom

power. Load-shedding episodes (2019, 2022-23) cut smelter output and moved the rhodium price violently.

• No exchange, no hedge: unlike platinum and palladium

(NYMEX futures, LBMA fixes), rhodium and iridium trade entirely OTC. The reference prices are Johnson Matthey base prices (published, twice daily) and dealer quotes. A consumer facing a squeeze has no futures market to run to — the same structural nakedness as gallium, at 1000× the price.

Price history (context, not live data)

• Rhodium: ~$600/oz (2016) → ~$29,000/oz (Mar 2021) → ~$4,000-5,000/oz

(2023-25 normalisation). A ~48× round trip in five years — the most violent price path of any metal we cover, driven by emissions rules colliding with inelastic by-product supply.

• Iridium: ~$500/oz (2016) → ~$6,000/oz (2021 peak) → ~$4,500-5,000/oz

plateau. The hydrogen-scenario demand wall keeps the floor high.

Transmission chain

South African PGM reef → Rustenburg/Marikana smelters (Eskom power) → precious-metal refineries (ZA, plus Johnson Matthey UK, Heraeus DE, BASF) → autocatalyst coaters (Rh) and electrolyser / crystal-growth manufacturers (Ir) → every diesel/gasoline vehicle's emissions system; every PEM green-hydrogen project.

Honest coverage notes

• Production shares are on a combined Rh+Ir basis from the

standard USGS MCS / Johnson Matthey PGM-survey pattern, labelled approx pending an exact survey cite.

• Prices in this dossier are historical context, not a live

feed — no free daily Rh/Ir source exists (JM base prices are published but not redistributable as a feed).

• Ruthenium, the third minor PGM (~30 t/yr, chip resistors and

hard-disk media), is not yet scored — same chokepoint shape; a candidate for a later addition.