Fire assaying is the oldest and most reliable method of determining gold and silver in rock or concentrate samples. This method is still the industry standard. It is called "fire" assay because it involves smelting the sample which has been mixed with lead oxide. Until electric furnaces were available, samples were smelted literally in a fire.

This is a 290 page digital manual explaining the complete process of fire assaying, presented in .pdf format on a Gift Quality DVD.