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| Element | Limit | Where it comes from |
|---|---|---|
| Arsenic, zinc concentrate | Below 0.6% | Fastmarkets zinc spot concentrate assessment |
| Cadmium, zinc concentrate | Below 0.33% | Fastmarkets zinc spot concentrate assessment |
| Mercury, zinc concentrate | Below 0.06% | Fastmarkets zinc spot concentrate assessment |
| Arsenic, lead concentrate (China) | Lowered from 0.7% to 0.6% | Fastmarkets report citing sources; SMM |
| Arsenic, zinc concentrate (China) | Capped at 0.4% | Fastmarkets report citing sources |
China's standard GB/T 20424-2025 names lead, mercury, cadmium, arsenic, thallium and fluorine among the harmful elements it limits. The Chinese limits above were reported by market sources, so confirm them with the buyer before shipping.
What a concentrate is
Mined lead and zinc ore is milled and concentrated at the mine to raise the metal content before it is shipped. The concentrate is what trades: smelters buy it, recover the metal and keep a treatment charge for doing so. Zinc concentrate goes to zinc smelters and lead concentrate to lead smelters, and many mines produce both.
For production, reserves, refined metal prices and recycling, see the zinc and lead profiles in the library.
Why harmful elements decide the sale
A smelter pays for the contained zinc or lead, and charges for elements it has to deal with. Arsenic, antimony, mercury and cadmium are the usual ones. In one published sample purchase contract, the buyer deducts US$3.00 per dry tonne for each 0.10% by which arsenic plus antimony exceeds 0.7%, in proportion for part-steps. That is one example, not a market rate, and every contract sets its own.
Above a certain level, a cargo may not be accepted at all. Fastmarkets reported that China was tightening its import limits on impurities in metal concentrates, and SMM reported a new specification limiting harmful elements in lead concentrates. If you are selling into China, ask the buyer for the limits currently applied to the cargo, in writing.
Moisture, weight and shipping
The Chinese lead-zinc bulk concentrate standard YS/T 452 sets moisture below 12%, and below 8% in winter. Contracts refer to the transportable moisture limit (TML) and flow moisture point of the cargo, and the cargo is shipped under the IMSBC Code. Mineral concentrates are listed among cargoes that can liquefy, which are Group A cargoes, so the shipper must provide a declaration of moisture content and TML before loading.
How assays are settled
Concentrate contracts usually settle on an assay exchange: buyer and seller each have the cargo assayed, and if the two results fall within an agreed splitting limit they are averaged. If they do not, a sample goes to a third laboratory, the umpire, whose result decides. The weight is normally set by a draft survey at the load port, with sampling and moisture determination done by a neutral party. The umpire, the splitting limits and the rules for who pays should all be named in the contract before shipment.
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Frequently asked questions
What is a zinc concentrate?
Zinc ore that has been milled and concentrated to raise its zinc content, typically sold to smelters. A Fastmarkets benchmark assessment lists 45 to 55% zinc.
Which elements are penalised in lead and zinc concentrates?
Arsenic, antimony, mercury and cadmium are the usual ones, along with silica and other impurities in some contracts. Limits and penalty rates are set in each contract.
What moisture is allowed in lead and zinc concentrate?
The Chinese industry standard YS/T 452 for lead-zinc bulk concentrates sets moisture below 12%, and below 8% in winter. Shipping also depends on the cargo's transportable moisture limit.
What is an umpire assay?
A third laboratory, agreed in advance, that analyses a sample when the buyer's and seller's assays differ by more than the contract's splitting limit.
What is a treatment charge?
The fee a smelter keeps for processing concentrate into metal, deducted from what it pays the miner. It is set in annual benchmark negotiations and spot assessments.
Sources
- Fastmarkets: zinc spot concentrate TC price assessment notice
- Fastmarkets: China to tighten import thresholds for impurities in metal concentrates
- SMM: new specification to limit harmful elements in lead concentrates
- GB/T 20424-2025 (China) concentrate harmful-element standard
- YS/T 452 (China) lead-zinc concentrate standard
- Sample purchase contract with an arsenic and antimony penalty
- Dataminesoft: assay rules in sales and purchase contracts
- UK MCA Marine Guidance Note 511 (IMSBC Code shipper's documents)
- USGS Mineral Commodity Summaries 2026: Zinc
- USGS Mineral Commodity Summaries 2026: Lead
Specifications published by index providers are revised over time. Where a figure comes from a pricing notice, confirm the version currently in force with the publisher before you use it in a contract. Corrections are welcome.