Cupellation is an oxidizing fusion of an alloy of lead, gold, and silver in an absorbent vessel known as a "cupel"

During cupellation the lead is oxidized to litharge (PbO), most of which is absorbed by the cupel, leaving at the finish a bead of gold, silver, and most of the platinum and associated precious metals that may be present.  The bead is subsequently treated to determine its precious-metal content.  Cupels are typically made from magnesia MgO (sometimes mistakenly referred to as magnesite), bone ash, portland cement, and other materials.

The lead button for cupellation is typically generated in the crucible fusion from the fire assay process, but can also be produced by a scorification assay, or a bullion assay where the precious metal is wrapped in lead foil.  Typical cupellation furnace temperatures in gold and silver assays are 1650-1700F, but can vary with technique, air flow volume, and cupel material.

Fire Assay Cups	magnesite and ash bone cupels	Cupels Use Bone Ash	Ceramics Cupel Pure Bone Ash
Calcium Phosphates (Bone Ash) ceramic	High purity magnesite cuples	Magnesia Cupel For Gold Melting	Bone Ash Cupels

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