Standards & Blanks. The 5 uses you need to know.
Wednesday 27 May 2026
The JORC Code 2012 requires competent persons to demonstrate that adequate QA/QC has been applied to sampling programs before results can support a public resource statement. That requirement exists because laboratory errors, if undetected, flow directly into grade estimates, resource classifications, and ultimately into investment decisions built on data nobody checked.
Certified reference materials and blanks are the primary tools for catching those errors at the source. Each one tests something specific. Here is what each one does and what goes wrong if it is skipped.
1. Insert a certified reference material to test laboratory accuracy.
A CRM is a sample of known grade, certified by round-robin analysis across multiple independent laboratories. When your CRM result deviates from its certified value, it indicates a laboratory bias. That bias applies to every sample in the same batch. Without a CRM in the batch, systematic laboratory error is invisible until it appears in your variography. Insert one CRM per 20 samples as a minimum standard.
2. Insert a coarse blank to test for cross-contamination in crushing and milling.
A coarse blank is barren material, typically matching your host rock, that passes through the full preparation chain alongside your samples. If the blank returns elevated values for your target analyte, the crushing or milling equipment is carrying residual material from a previous high-grade sample into your batch. A pulverised blank bypasses the preparation stage entirely and misses this. The coarse blank is the only tool that catches it.
3. Insert a field duplicate to test sampling precision.
A field duplicate is a second sample collected at the same point, split in the field from the same material. It tests whether your sampling method produces reproducible results. Poor duplicate precision signals that the sample is heterogeneous, the splitting method is inadequate, or the sample interval is too short to be representative. Resource estimation requires demonstrable precision. A programme without field duplicates cannot demonstrate it.
4. Use a low-grade CRM in low-grade programmes and a high-grade CRM in high-grade programmes.
CRMs must be matrix-matched and grade-matched to the samples they accompany. A CRM with a certified grade far above or below the typical sample population forces the laboratory to recalibrate its instrument range for your QC material, which distorts the calibration applied to your project samples. Match the CRM grade to the grade range of the programme it is monitoring.
5. Review CRM and blank results batch by batch, not at the end of the campaign.
A laboratory failure identified in batch 3 can be investigated and reanalysed before batches 4 through 40 are processed. The same failure identified at the end of a 2,000 sample campaign means a decision about whether to reassay the entire programme. Systematic review after every dispatch is not administrative overhead. It is the only way QA/QC functions as a control rather than a retrospective audit.
One thing to avoid. Do not insert an ore-grade CRM into a batch of low-grade or barren host rock samples. An ore-grade standard forces the laboratory to extend its calibration curve far beyond the range of the surrounding samples. This degrades the accuracy of every result in that batch and can trigger instrument recalibration mid-run. Match your standards to your samples. The CRM is there to test the lab, not to challenge it.
Good QA/QC does not find problems after the fact. It stops them becoming problems in the first place.
At Norwest Exploration and Mining Services, we specialise in rapid deployment of geologists and field technicians who understand QA/QC as a professional standard, not a compliance checkbox. Whether you need one person or a full field crew, we place the right people fast.
Looking to build a field team that gets QA/QC right from day one? Contact Norwest directly or visit our profile.