Addressing sampling representativeness for copper, lead and zinc concentrates, the two sides jointly set operating rules for load-port sampling, sample reduction and retention.
In June the company completed a joint revision of its mineral sampling and verification procedures with a third-party testing institution. The new procedures cover load-port sampling points, sampling tools, sample reduction, sealing and retention periods.
Under the new procedures, critical lots follow a “double-test, double-retain” rule: each trading party keeps a sealed sample, the laboratory keeps a backup, and either side may request a re-assay within the retention period.
The company’s view is that most disputes in mineral trading arise in sampling, not in assaying. Standardising sampling is worth more than arguing over a grade figure after the fact.