AGR uses different assaying methods:
The AGR-certified laboratory engineers use the Fire Assay Method, also known as the Cupellation Method to determine the concentration of Gold and Silver. A small sample of material has its precious metals chemically separated from the impurities and base metals contained in the material. The precious metals remaining are then compared to the original starting weight of the sample to determine the composition percentage. The Fire Assay analysis has an accuracy of 1 part in 10,000.
ICP – Induction Coupled Plasma
The ICP is a sophisticated hi-tech instrument used for detecting trace amounts of metals in a sample. The ICP is sensitive and accurate enough to detect elements down to parts-per-million (PPM). In an ICP analysis, a small sub-sample of the material is dissolved in several acids and the resulting liquid is vaporised at a very high temperature in a mass spectrometer. Reading the peaks of the mass spectrum output allows the operator to determine which metals are present and what their concentration is.
The X-ray fluorescence is a non-destructive technique that is suitable for fast assaying requirements. It has an accuracy of 5 parts per thousand and is well suited to relatively flat and smooth surfaces. It is a quick technique that takes about three to ten minutes and the computer can automatically print out the results. The content of other alloying metals is also measured.