In this video Lynda Bloom discusses why homogeneity is important and why some manufacturers find it difficult to achieve good homogeneity in gold standards (certified reference materials).
A look at 5 key things to look for when choosing a CRM supplier that maximise your chance of a successful quality control program.
A short video about key concepts of quality control for mineral exploration
Abstract
All resource models depend on assays and an assumption that representative subsamples were assayed accurately. Resource estimation, for gold projects in particular, requires an understanding of routine sample preparation and assay methods.
Assay quality control programs have become near ubiquitous since NI43-101 reports were introduced nearly 20 years ago. There are no specific rules for the rate of insertion, actions required for quality control failures and other questions that frequently arise. Statistics from studies of publicly available NI43-101 reports will be presented that have helped Analytical Solutions Ltd. develop guidelines for clients to achieve “industry standard” compliance.
Achieving a representative sample for assay is a significant challenge for some gold projects. Part of the challenge is balancing the cost of sample preparation and maximizing the probability of achieving a representative sample. Justifying higher costs for sample preparation should be based on duplicate data and the correct estimation of precision. The industry uses a wide range of statistics to estimate precision; this has caused confusion about optimum results.
The preferred methods of calculating precision using the coefficient of variation and visualization of the data are presented.
The focus of this paper is the control and improvement of analytical data quality for exploration geochemical surveys. Many types of geochemical surveys (hydrogeochemistry, biogeochemistry, selective extractions and rare earth lithogeochemistry) take advantage of modern technology, such as ICP-MS, and require measurement of elements at the sub-ppb level.
This third edition expands the original mandate of surficial geochemical reports to include multiple types of geochemical surveys with survey-specific recommendations.
Edited by Lynda Bloom and Owen Lavin.
Abstract
Independent quality assurance and quality control (QA/QC) programmes are required by reporting codes for publicly listed companies and are necessary to optimize data quality at all stages of the sampling, preparation and analytical processes involved in mineral exploration, resource estimation and mining grade control. QA/QC programmes should be adjusted over time to meet changing requirements in data quality at different stages of mineral resource development and exploitation. Certified reference materials are used to monitor accuracy and bias at the project laboratory relative to consensus values for the material from round-robin certification analyses. They are also used to monitor drift over time within an individual laboratory and to identify significant failures in QC at the analytical batch level caused by abrupt changes in concentration related to re-calibration of instruments or procedural changes at the laboratory. Duplicate analyses of sample material are generated at key stages of sampling and preparation to estimate the precision of data generated at each stage. Invariably, the largest source of uncertainty occurs during the initial sampling. Coarse blanks are used to monitor cross-contamination between samples or from sample preparation equipment. Furthermore, each of these QC sample types can be used to discover possible sample mix-ups.
It has been almost 25 years since Bre-X inspired the implementation of technical reports worldwide. The reporting requirements triggered the use of quality control (QC) materials (blanks and certified reference materials) and quality improvements at commercial laboratories. Many aspects of monitoring QC have been automated