Lead and zinc almost always travel together — they crystallise from the same hydrothermal fluids in polymetallic sulphide deposits, with galena (PbS) and sphalerite (ZnS) usually accompanied by chalcopyrite, pyrite, silver-bearing sulphosalts, and a long list of penalty trace elements. Separating them into clean LME-grade refined metals is a five-stage chain with named processes at each step. Procurement teams and exporters who understand the chain place their contracts more precisely — and recognise where the by-product credits and penalty deductions live. For which emerging-region lead-zinc deposits actually feed this chain, and the project economics behind them, see lead-zinc in developing countries.
Stage 1: Mining the Polymetallic Sulphide Body
Most lead-zinc mining is underground using cut-and-fill, room-and-pillar, or sublevel-caving methods depending on ore-body geometry. Major operations: Red Dog (Alaska — zinc-dominant), Vedanta's Hindustan Zinc operations (Rampura Agucha, others — Indian), Glencore's Mt Isa (Australia), Korea Zinc's portfolio (smelter-side feed). Pakistani Duddar in Balochistan is the largest formal Pakistani zinc-lead operation. Run-of-mine grade is typically 3–10% combined Pb+Zn with the balance gangue minerals. ILZSG monthly bulletins track aggregate global mine output.
Stage 2: Comminution to Liberation Size
Jaw + cone + ball mill / SAG mill crushes and grinds run-of-mine ore to typical 50–150 μm P80, releasing galena and sphalerite particles from the gangue matrix. The target P80 depends on the ore-body specific mineralogy — finer grinding improves liberation but raises energy cost and creates flotation problems with ultra-fine particles.
Stage 3: Differential Flotation — Where Pb and Zn Separate
Differential flotation produces separate Pb and Zn concentrates from the same feed:
- Lead circuit: xanthate collectors (sodium ethyl or isopropyl xanthate, dose 30–80 g/t), pH 8–9, with sphalerite depressed by zinc-sulphate-cyanide complex. Galena floats first, recovered as Pb concentrate at 50–70% Pb.
- Zinc circuit: tailings from lead circuit are conditioned with copper sulphate (activates sphalerite surfaces, dose 100–300 g/t) and xanthate collector. Sphalerite floats as Zn concentrate at 50–60% Zn.
By-product silver typically reports to the lead concentrate (sulphosalts associate with galena); some operations have parallel circuits for high-grade silver if economics support it.
Stage 4: Smelting — Three Distinct Routes
Lead concentrate smelting traditionally uses lead blast furnace (with prior sintering); modern operations use direct-smelting flash processes (Kivcet, Ausmelt/Outotec ISA furnaces). Output: lead bullion at 95–99% Pb with silver, gold, antimony, copper, and bismuth as solubles. Zinc concentrate smelting splits into two routes:
- Roast-leach-electrowin (RLE): dominant modern route. Roast at ~900°C to ZnO + SO₂ (acid by-product), leach in H₂SO₄, electrolyse to SHG zinc cathode.
- Imperial Smelting Furnace (ISF): simultaneous Pb and Zn smelting in a single furnace; declining in importance but still operating at some sites.
Stage 5: Refining — Harris Process for Pb, Electrolytic for Zn
Lead bullion is refined via the Harris process (selective oxidation of impurities Sb, As, Sn) or Parkes process (silver extraction via zinc-silver alloy formation) followed by Betts electrolytic refining for LME spec (Pb ≥ 99.97% per LME specification). Zinc is electrolytically refined to Special High Grade (SHG, ≥ 99.995% Zn) — the LME zinc spec. Silver from lead refining is the largest by-product credit (often 200–500 g/t in concentrate; smelter-side recovery 90%+).
By-Product Economics
Silver, gold, copper, cadmium (from zinc), indium (from some zinc smelters — particularly Korea Zinc), germanium, and gallium are recovered as by-products. Silver alone can contribute 5–15% of lead-zinc cargo value depending on concentrate grade. By-product credit terms are bilateral and specifically negotiated in concentrate contracts; smelter disclosure varies.
Where Lead-Zinc Extraction-Reads Trip Up
- Interchanging galena (PbS) and cerussite (PbCO₃). Sulphide vs oxide; different processing routes (flotation vs leach).
- Stating "lead concentrate trades on the LME." The LME contract is for refined lead at 99.97%. Concentrate trades against LME minus TC.
- Omitting silver assay from any lead concentrate contract. Silver payable is a meaningful share of cargo value.
- Assuming Imperial Smelting Furnace operations are widely available. Most are aging; modern projects use roast-leach-electrowin.
- Stating zinc payable as "100% of contained." Standard zinc concentrate payable is 85% of contained Zn with minimum 8% unit deduction — the largest payable-deduction structure in major-metal concentrates.
- Equating lead-zinc concentrate grade with refined metal price. Concentrate grade × LME × payable − TC = approximate cargo value; the calculation is multi-variable.
- Extrapolating Hindustan Zinc operating costs to other regions. Indian, Australian, Mexican, and Pakistani operations have very different cost structures.
What This Means for Pakistani Lead-Zinc Trade
Pakistani Duddar concentrates and other regional production typically sell to Chinese custom smelters (the largest global concentrate-import market) with assay packs covering Pb, Zn, Ag, and the standard penalty elements. Bare Syndicate trades lead ore (galena 40–70% Pb) and zinc ore (sulphite and oxide, 15–30% Zn) from Pakistani operations with full assay-pack delivery.
Next step: Discuss lead and zinc supply from Bare Syndicate's Pakistani mineral operations — galena and sphalerite concentrates with assay-pack-verified payable and penalty profiles.
Additional Market Context
The standard reference sources for commodity-trade procurement: USGS Mineral Commodity Summaries (annual, mineral-by-mineral chapters), ICSG / ILZSG / ICDA monthly bulletins (commodity-specific), Fastmarkets / Argus / Platts indexed pricing (subscription, with selected free coverage), LME / COMEX / SHFE / GFEX / ICE exchange data (daily settlements), IEA Critical Minerals Outlook (annual scenario analysis), and Wood Mackenzie / CRU / Roskill specialised services (subscription). The OECD Due Diligence Guidance covers supply-chain due diligence across minerals.
For Pakistani and Asian counterparties specifically, Pakistan State Oil, OGRA, OCAC, Hindustan Zinc, Vedanta, and ENRC (Kazakh chromite) provide regional supply-side data. Bilateral US Critical Mineral Arrangements (Japan, UK, EU in negotiation) shape the regulatory framework for cross-border mineral trade.
Last reviewed: 2026-05-16. Process references are industry-standard; specific operations vary by mineralogy, plant design, and counterparty specifications.
