Assaying of precious metals  
SAO offers testing of precious metals e.g Gold, Silver, Platinum and Palladium for purity and content using both the Fire Assay (Cupellation) test method and the X-Ray Fluorescence (XRF) spectroscopy test method.
 
Fire Assay Test Method
The Fire Assay (Cupellation) test method is the most accurate method for testing the purity of gold, with an accuracy of about 0.02%. It involves taking a small scraping from the article, typically about 250 milligrammes, weighing it accurately, wrapping it in lead foil with some added silver, cupelling it in a furnace at about 1100°C to remove all base metals and then placing the resulting gold-silver alloy button in nitric acid to dissolve out the silver (known as 'parting') and re-weighing the resulting pure gold.  

X-Ray Fluorescence Spectroscopy Test Method
The X-Ray Fluorescence (XRF) spectroscopy test method is the latest method used by SAO for testing of precious metal articles. This method is non-destructive, so samples will not be damaged or destroyed. This allows jewellery pieces with exquisite designs to be tested which cannot be done with the Fire Assay test method due to the high costs of repairing or redoing the item. It is also a very quick method, taking about 20 - 30 minutes per test for an accurate result, as compared to the Fire Assay method which take up to 5 hours to complete. Besides analysing the gold content, the XRF test method is able to analyze all alloying metals present in the sample including the thickness of any coating present in the sample.