flyinglite, this come from an article on fire assay. Hope it helps

After cooling, the metallic lead "button" at the bottom of the mold is separated from the glassy slag which is discarded.

The metallic lead button is placed into a cupel, which is a small dish made from bone ash, and placed into a cupelling furnace. In the "cupelling" process lead metal turns back into oxide which volatilizes away from the precious metals and soaks into the bone ash cupel, leaving the minute amount of precious metals as a metallic speck of metal called a "bead" on the bottom of the cupel.

Next, the bead is weighed on a microbalance to determine the amount of gold and silver that was extractable from the original ore sample. The bead is next heated in hot nitric acid which dissolves away the silver, leaving any gold that may have been present. This step is called "parting" because the nitric acid "parts" the gold from the silver-gold mixture in the bead.

The parted bead is then carefully weighed and this amount of gold is related back to the weight of ore or concentrate sample in the first crucible that was fired.

In more modern laboratories, the bead of precious metals that is recovered in the cupel after the lead has been removed is dissolved in aqua regia. The resulting solution is then analyzed by atomic absorption spectrometry, allowing the grade of gold and silver in the original sample to be back calculated.