Assay
A chemical test performed on ore or rock samples to determine the concentration of valuable minerals.
Detailed Definition
An assay is a chemical analysis of ore, rock, or mineral samples to determine the type and concentration of valuable metals or minerals present. Assays are fundamental to mineral exploration and resource estimation.
Types of assays
Fire Assay: - Traditional method for precious metals (gold, silver, platinum) - Uses heat to separate metals from ore - Considered the most accurate for gold
Chemical Assay: - Uses chemical reagents to dissolve and analyze samples - Common for base metals (copper, lead, zinc) - Various methods (ICP, AAS, XRF)
Sample preparation: - Rock samples crushed and pulverized - Representative portion selected - Sample split for duplicate analysis
Quality control: - Certified reference materials (standards) - Blank samples to detect contamination - Duplicate samples for precision - Inter-laboratory checks
Reporting: Assay results reported as: - Parts per million (ppm) for trace elements - Grams per tonne (g/t) for precious metals - Percentage (%) for base metals and industrial minerals
Accurate assaying is essential for resource estimation and mine planning.
Related Terms
Mineral Resource
A concentration of minerals with reasonable prospects for economic extraction, classified as inferred, indicated, or measured.
Ore
Rock or material from which valuable minerals or metals can be profitably extracted.
Grade
The concentration or proportion of valuable mineral content in ore, expressed as percentage or grams per tonne.