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Author: Admin | 2025-04-28
Analysis (Table 21). During grade control, QAQC should include field duplicates and certified reference material (CRM) submission (e.g., minimum three CRMs at a range of grades including blanks). Laboratory QAQC will include internal CRMs, pulp duplicates, umpire sample submission, pulp screen tests, and contamination tests. In particular, duplicate field samples provide a measure of variability of the entire sampling process.Documentation of sample collection and laboratory activities is an important part of QAQC, and staff training and monitoring. It is the opinion of the authors that quality samples flow from well-trained and experienced personnel. Operations should ensure that all grade control staff are trained in sampling and during their first few months have adequate mentoring. This will be additional to all standard operational and safety training. Proper training will be facilitated by well-written and illustrated documentation. Training and mentoring should be linked to continuous quality improvement, where protocols are internally and externally audited at least annually. On-going supervision and periodic re-training are recommended, where activities must be practical-based at the rock face and not simply in the classroom. 8.2. Chain of CustodyChain of custody (COC) procedures are particularly relevant if samples inform a resource estimate. Chain of custody must provide a documented, legally defensible record of the custody of samples from collection through analysis [35]. A sample is considered to be in custody if it meets at least one of the following conditions, where the sample is: in someone’s physical possession or view, secured to prevent tampering, or secured in an area restricted to authorised personnel.Chain of custody procedures in the underground environment are more difficult than for surface-based activities. The greatest risk of sample tampering is during collection, and prior to the sealing of sample bag(s) or core trays. At the mine face, samples should be bagged and sealed with a wire tie. Drill core trays can be covered with a metal lid and strapped. Samples and trays should be returned to surface as quickly as possible via the most efficient means.A sample or core record sheet can be used as a COC document to track sample progress from face/rig, to core shed and laboratory. Face, grab, or core samples will need to be securely transported to the laboratory, which may be either onsite or offsite. In either case, the COC document can be used to track progress and record handovers. Where samples have a journey to an offsite laboratory, then transport should be secure. 8.3. Errors along the Sampling Value ChainThe results of duplicate sampling programmes document the magnitude of errors across the sampling value chain (Table 1, Table 2, Table 3 and Table 4). These generally show that a large component of the total error is introduced during
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