Improved Reliability of Resource Estimates Based on Assay Quality Control

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.
Key Words: Assays, sampling, precision, duplicates