A metallurgical assay is a compositional analysis of an ore, metal, or alloy.  The most elaborately accurate, but totally destructive, precious metal assay is fire-assay.  In the case of fire assaying of gold and platinum ores, the lengthy time required to carry out an assay generally is offset by carrying out large numbers of assays simultaneously The principal advantage of fire assay is that large samples can be used, and these increase the accuracy in analysing low yield ores.  The sample of rock is heated in air to about 1000°C