QAQCThe aim of a QAQC program is to bring confidence to a company’s claim that their reported gold analysis results are true. A good QAQC program will identify problems in the sampling and analyses stream so that they may be fixed as soon as possible.
In reality, there is no such thing as an absolute ‘true’ or correct gold analysis result, just the ability to estimate how close to reality has been achieved. In practical terms QAQC can demonstrate results are not biased to a significant degree. Although applicable to all gold analysis reporting, QAQC is particularly important where results form the basis of a resource estimate. For example if the laboratory completing gold analysis for resource drilling is returning gold grades with 20% higher values than reality, the resource estimate will be 20% higher than reality. A mine will then be designed around an inflated resource and the company will then produce 20% less gold than expected. At worst the mine will fail because the profit margin is wiped out by the decreased gold production. At best the company will still be profitable but receive a severe valuation downgrade for not meeting gold production forecasts. With QAQC, as with most areas of resource estimation, there is no absolute in terms of what is and is not acceptable. Ultimately it is up to the Competent Person who is signing off on the resource estimate to make a call on whether QAQC is sufficient. The level of QAQC will impact the both the category of resource (Inferred, Indicated, Measured) as well as helping decide if the resource can be claimed to exist at all. The actual definition of QAQC is that: QC means Quality Control. In gold resource context this means inserting special QC samples into the regular sample stream. These QC samples are designed to test that the laboratory is reporting un-biased results and are usually inserted at regular intervals, for example every 10 or 20 regular drill samples. Types of QC samples will include: -Standard Reference Material. Powder certified to be a known gold value. If a company submits to the lab a standard reference material with known gold grade 1.51 g/t Au and the result comes back 2.34 g/t Au, then the company is alerted that all their regular sample results could be being over-estimated. The acceptable deviation from the known value is usually ±5%. -Blanks. This is material known to have near zero levels of gold. If a blank sample comes back from the lab with a value of greater than zero (effectively the lower detection of the analysis method, usually 0.005 g/t Au for resource drilling Fire Assay methods) then the company is alerted that there is contamination occurring at the lab that allows gold results to be reported in samples that are in fact without gold. -Duplicates. Actual drill samples are split into two (can be done at various stages, but usually after the first coarse 2mm crushing stage or for RC drill sample a split of the original interval) and analysed separately. If the results between each sample vary by more than ±10% the company knows the analysis is not reliable. -Umpire Checks. After analysis by the main laboratory some residual sample pulps are sent to a second laboratory for re-analysis. If the second analysis returns results ±5% different to the original analysis the company has cause for concern. QA means Quality Assurance. In gold resource context this means being able to demonstrate with confidence that the sampling procedure from start to finish does not contain any systematic errors. Basically it means being able to show that the company did a good job through the whole sampling and analysis process. It doesn’t mean being without error, as this is unavoidable, but showing that results are within an acceptable degree of bias. |