Fire Assay Cupellation
A sample must be taken from the article and that maybe done through cutting, scraping or drilling. Each sample is around 0.1 gram.
Silver is added to the samples before wrapping it in pure lead foil and placing it in a special porous crucible called a cupel. This is placed into a high temperature furnace at about 1100°C. The silver is added to dilute the gold content (known as Inquartation). The samples are oxidised to form a liquid slag. This slag is absorbed into the cupel to leave a small gold-silver alloy bead. On cooling, this bead is rolled flat into a thin strip to increase its surface area. It is coiled loosely into a "cornet" and the silver is dissolved out in 2 stages of nitric acid. Once the silver has been removed from the samples, the remaining gold content is pure and can be washed, dried and weighed.