Accurate sampling practices in the mineral industry are critical for determining the chemical, mineralogical and physical characteristics of ores and mineral products for resource evaluation and utilisation, feasibility studies, process design and optimisation, quality control, metallurgical accounting, and ultimately commercial sales. Sampling is the first step in the measurement chain and is where the measurement process all begins, so if the sample that is collected is not representative, then the whole measurement chain is compromised at the outset. However, frequently the responsibility for sampling is entrusted to personnel who do not fully appreciate the significance and importance of collecting representative samples for analysis, and quite often everyone seems satisfied as long as some material is collected and returned to the laboratory for analysis. In the case of sample stations, cost is often the main consideration rather than sampling correctness (unbiasedness), which is unacceptable and needs to change. It is important that sampling experts are involved in the design stage at the outset to avoid structural design flaws and the subsequent need for expensive retrofits to address major and sometimes even fatal problems. Furthermore, ongoing audits of performance need to be conducted to ensure sample stations are adequately maintained and continue to conform to correct sampling principles. Provision also needs to be made for duplicate sampling to monitor the precision achieved in practice on an ongoing basis for quality assurance purposes. The examples used and commented upon here relate to one of the more difficult industry sectors with respect to correct sampling practices, material and constituent type (e.g. ores, concentrates and mineral aggregates), tonnages, process stream flow rates, and wear and tear, and as such provides the ideal showcase for the intended message which applies essentially to all technologies and industries.
Publication date: 9 June 2015