Cupel

A cupel (small dish) of bone ash with a shallow depression containing silver droplets which have failed to coalesce. Part of the rim is missing. The separation of precious metals (gold and silver) from lead ore was done by a process known as cupellation. In this process, the metal to be refined was melted with oxidised lead forming a litharge (lead oxide). This dissolved any base metals present, and separated them from the precious metal component. The litharges was continously removed; either in liquid form or by absorption in the hearth lining. Small cupels, usually made from bone ash, were used for the process of fire assay to determine the precious metal content of the ore or a metal sample.