Fire Assay (Cupellation)
It is one of the oldest and the most accurate techniques of assaying gold.
This ancient technique is first referenced by the Egyptians in a Cuneiform tablet dating back to around 1360 BC. It remains the most accurate technique for gold assay and serves as the standard technique against which all others are compared.
The accuracy of assaying is affected not only by the assaying expertise, but also the sampling of the materials done. The sampling size should be representative of the materials being tested. It should be grouped according to its fineness.
The accuracy of the fire assay method is about 2 parts per ten thousand.