Ore assay is the analytical process of determining the concentration of valuable minerals or elements contained within a sample of rock or ore, providing quantitative data used to estimate grade, guide mine planning, and support financial reporting of mineral resources and reserves. In gold mining, fire assay remains the industry-standard technique, in which a sample is fused with fluxes at high temperature to collect gold and silver into a lead button that is subsequently refined and weighed, while diamond assaying involves processes such as dense media separation or X-ray sorting of bulk samples to determine carat content per tonne. Iron ore assays typically measure iron content alongside impurities such as silica, alumina, and phosphorus using techniques like X-ray fluorescence, while bauxite assays focus on determining alumina content, silica content, and reactive silica, which influence the ore's suitability for the Bayer refining process. Assay results are derived from samples collected via drilling, such as diamond core or reverse circulation drilling, as well as from blast hole sampling and processing plant streams. Rigorous quality assurance and quality control protocols, including the use of standards, blanks, and duplicate samples, are essential to ensure assay accuracy, since errors can significantly distort resource estimates, mine planning decisions, and ultimately the financial viability assessments of a project.
