Sampling of bulk mineral commodities for international trade, such as iron ore, coal and a wide variety of mineral concentrates, is generally carried out in accordance with National or more commonly International (ISO) Standards developed to provide representative samples for subsequent analysis and payment. Because commercial transactions are involved, clearly getting the sampling right is critically important, and poor sampling practices can potentially lead to substantial financial losses for one of the parties involved. The “golden rule” for correct sampling is that “all parts of the material being sampled must have an equal probability of being collected and becoming part of the final sample for analysis”. If this rule is not respected, then bias is easily introduced and samples are not representative.

While on-site observations indicate that the adoption of good sampling practices is improving, ensuring that samples are representative continues to be an ongoing challenge. This is often due to cost-cutting measures where sampling facilities, equipment and operations are the first to suffer, or it may just simply be due to ignorance of the requirements for collecting representative samples despite the existence of National and International Standards as well as high level sampling courses presented by international experts. More often than not, the company focus is on maximizing production tonnage rather than product quality and its measurement. Areas where significant issues continue to occur include:

• Primary cutter design for ever increasing high-capacity streams
• Correct operation of cross-stream secondary cutters
• Crusher performance and ongoing maintenance, particularly in relation to product particle size
• Retained sample mass versus particle size
• Extraction and handling of moisture samples
• Equipment maintenance.

Timely ongoing maintenance of sample stations is critical and needs to be a high priority to ensure correct performance. A “set and forget” strategy simply does not work. Sampling needs to be given the commitment it deserves by company management, particularly through correct sample plant design, timely equipment maintenance, and appropriate staff training and awareness.