Fire Testing or Assay
It is also called as melting test, while this is the most complex and also accurate testing method. It is a standard method for valuing gold and silver, but commonly at major mining refineries. In this process precious metal is melted down and then the sample is separated chemically from the additional metals. During the separation process it is dissimilar for each precious metal, using an array of chemicals. We suggest this fire assay method when or where acid or XRF test are not best option to use.
Working – In this method a precious metal sample is melted and mixed with lead oxide along with some control chemicals. The lead in the mixture unites with the samples precious metal and to cool down the entire mixture is transferred into a mold. Because the lead is so thick, it sinks to the mold’s bottom, where it is chipped off and placed into a cupel and melted again. The lead is immersed with the cupel, by leaving the precious metal. While precious metal is then calculated against the size of the remaining sample to find out its overall purity. This testing method is the best way to determine the amount and purity of precious metals. PMROFCA recommends fire assay or melting test because it gives accurate results.