Quality Assurance/Quality Control of Geochemical Assay Data


Course Brief

Nearly all decisions made about a mining project, from exploration to mine closure are based on assay values obtained from sampled material. Most of these decisions commonly concern large sums of capital. Most international mining companies have implemented very strict rules for the reporting of geochemical results to ensure that data is authentic, representative and underpins reliable mineral resource and ore reserve estimation.

It is essential to have high quality standards and controls in place to increase shareholder confidence, to ensure that the correct mining decisions are made and to minimize the risk associated with the assaying process.

The only way to ensure that results are reliable, is to implement a QC management practice that is designed to detect sampling errors, contamination, inconsistencies between sampling and results, salting, poor analyses, analytical procedure errors, laboratory bias, batch effects and incorrect numbering.

As an example, the South African Code for the Reporting of Exploration Results, Mineral Resources and Mineral Reserves (SAMREC Code, 2016) governs uniformity of Resource and Reserve reporting in the public domain and the principles of this Code are incorporated into the listing rules of the Johannesburg Stock Exchange (JSE).

According to these rules, any competent person who publishes the Mineral Resources of a company in the public domain is required to adhere to certain principles when using information provided to them by a third party. In this context assay information as supplied by the Laboratory Service Provider needs to be validated, verified and the nature of QAQC adopted to validate the assay information must be disclosed (Sections 12.3 e and 12.9 f of the JSE rules).

JSE rules section 12.9 f): “With respect to assaying the nature, quality and appropriateness of the assaying and laboratory procedures used must be outlined and whether the technique is considered partial, or total should be explained. The nature of quality control procedures adopted must be highlighted (e.g., standards, blanks, duplicates and external laboratory checks) including whether acceptable levels of accuracy (i.e., lack of bias) and precision have been established.”


QAQC programs are designed to monitor precision (reproducibility), to quantify bias (accuracy) and to give an indication of the origin of problems in the analytical process. Emphasis should be placed on presenting a clear picture of the reliability of the assay data, so that it can be confirmed that there is a good correlation between the procedures used in construction of the mineral resource model and the quality of the data used in that model. QA is information collected to demonstrate and quantify the reliability of assay data. QC consists of procedures used to maintain a desired level of quality in the assay database. QA can, to a certain extent, be added later in a program. QC, like safety, can only be performed in real time. Thorough QAQC programs are intended to monitor routine sampling and analysis

The course has been developed for professionals involved in competent person’s reporting, resource geologists, exploration geologists, data management, QAQC managers

The following Subjects will be addressed:

  • Definitions and Concepts
  • Protocols and Analyses
  • Reporting
  • QC material box
  • Milling time studies