Overview
Terbium carries two meanings of "green". Tb³⁺ emits at 545 nm and is the green primary of fluorescent lighting, white-LED conversion phosphors and X-ray intensifying screens. The same element at ~0.5% of magnet mass is what lets an NdFeB magnet hold coercivity at the working temperature of a wind generator or an EV traction motor. Terbium goes where dysprosium is no longer enough; grain-boundary diffusion exists precisely to use less of it.
For that half percent the buyer outside China pays a policy premium, not a cost: $1,094.68/kg inside China against $1,565/kg FOB — $470/kg, 43%, made of export duty, VAT and trader margin. In 2025 terbium joined the export licence list with six other medium and heavy rare earths. China supplies 85–90% of output and ~99% of heavy-group separation.
Terbium is not geologically scarce; it is scarce in separated form. It is dissolved right now in two streams industry already pays to manage: acid mine drainage (treatment is a permanent statutory duty) and phosphogypsum (3.7–6 bn t in stacks, +200–300 Mt/yr).
> Core technology and architecture: see ARBOK-VC (Vacuum Cracking).
Applications
Feedstock streams: phosphogypsum, fresh and from stacks; acid mine drainage of coal and sulphide basins.
Outputs: mixed Nd, Pr, Dy, Tb concentrate, or separated fractions where required; clean water; acid returned to process; radionuclides immobilised into 0.1–0.5% of volume.
End uses: high-temperature NdFeB magnets (traction motors, wind generators, defence), green phosphors.
Operating Principle
Phosphogypsum is dissolved in the acid medium the process generates itself — no reagent purchased — and the stream is separated by cold boiling under deep vacuum at ambient temperature, ~1 kWh/t of feed. No furnaces, membranes, consumable reagents or CO₂ from the recovery step. Separation of the rare earths happens in a single pass, inside the solution itself, without the classical cascade of hundreds of stages.
Key Parameters
Resource: Tb $1,094.68/kg China domestic, $1,565/kg FOB (spread $470, 43%). Dy $220.93/kg, Nd $124.87/kg, Y ~$35/kg. Tb is 5× Dy, 9× Nd, 45× Y.
China: 85–90% of terbium output, ~99% of heavy-group separation. Licence list since 2025.
Magnet loading: ~0.5% Tb by mass (0.5–2% bulk alloying; 0.2–0.5% via grain-boundary diffusion).
Phosphogypsum: 3.7–6 bn t accumulated, +200–300 Mt/yr; US up to 1.5 bn t. ~0.3% REO, Tb 0.2–0.5% of REO.
Resource arithmetic: annual increment 1,200–4,500 t Tb ($1.9–7 bn FOB); accumulated stacks 22,000–90,000 t Tb ($34–141 bn FOB).
AMD: total REE ~1–2 mg/L, heavy-enriched.
Architecture and Components
Arbok-SA route: dissolution + deep-vacuum cold boiling + in-solution separation. Radionuclide immobilisation into a small residue fraction. Shared platform with ARBOK-Lanthanum-Cerium, ARBOK-Dysprosium, ARBOK-Yttrium.
Advantages
Technical: takes terbium from streams no one assays for it; radionuclides handled as a small immobilised fraction rather than as a plant-wide problem.
Economic: acids and clean water of the same pass carry the process, so the rare earth fraction arrives at effectively zero marginal cost.
Strategic: bypasses the separation cascade, which is where the monopoly actually sits — not in the mine.
Integrations
Phosphoric-acid plants and their stacks; mine water treatment plants under reclamation bonds; connects to ARBOK-PHOSPHOGYPSUM, ARBOK-Scandium-REE, ARBOK-Neodymium.
Deployment & Operation
Assay of rock/stack and of drainage → configuration → install on the existing stream. Purchase or BOOM (PAY&GO + off-take at a discount to the export price).
TRL
Platform TRL 9; Arbok-SA route as per the lanthanum/phosphogypsum case. Terbium-specific field reference pending.
Market Potential
The West's constraint is separation, not geology. Terbium has no drop-in substitute in the highest-temperature magnet grades, is 0.5% of magnet mass and 100% of qualification, and carries a 43% political premium for every non-Chinese buyer.
Typical Project Economics
Phosphate site at 1 Mt/yr phosphogypsum: ~3,000 t REO, of which 6–15 t terbium = $9.4–23 M/yr at FOB. Nd, Pr and Dy report in the same basket on top. Acids and clean water carry the process.
Acid mine drainage: at 1–2 mg/L total REE a standard containerized module recovers ~100 kg of mixed oxides — thousands of dollars, not millions. What pays there is the displaced lime treatment and sludge, up to $270,000/yr per unit. Terbium is not the payback on that stream; it is the reason the concentrate is worth separating.
Risk Factors
REO grade and Tb share vary by phosphate source — assay per site; radionuclide-residue acceptance; conservative phosphate-industry adoption; Tb price is policy-driven and can move on a licence decision; terbium field reference pending.
Related Technologies
ARBOK-Dysprosium · ARBOK-Yttrium · ARBOK-Lanthanum-Cerium · ARBOK-Neodymium · ARBOK-Praseodymium · ARBOK-PHOSPHOGYPSUM