The laboratory measurement of metal content in a sample — the step that turns a promising-looking core in a box into a number.
The chemical analysis of rock, soil, or drill core samples to determine the concentration of valuable minerals or metals. Assay results are critical for resource estimation and are typically reported in parts per million (ppm) or grams per tonne (g/t) for precious metals.
Assays are the evidence base for everything else. Until they return, visual observations of mineralisation are exactly that, and companies that lean too heavily on visuals before assays are worth treating carefully.
Turnaround at commercial labs is often measured in weeks to months and lengthens in busy markets, which is why drill programmes and news flow are so frequently out of step.