What is an Assay Office (& what are the purity testing methods?)

What is an Assay Office? 

First, assay refers to the testing of a metal to determine its purity. Assay offices are therefore institutions set up to test the purity of precious metals. This is done to protect consumers from buying fake items.  

Assay offices randomly test batches of goods from manufacturers and if the metal contents of an item are found to match or be better than supposed (22K/916 gold items contain at least 91.6% of gold), the assay office will stamp their hallmark to certify it.  



What is Singapore Assay Office? 

Set-up in 1979, Singapore Assay Office (SAO), a division of Singapore Test Services, is an established accredited assaying and hallmarking office, reinforcing consumer protection among shoppers, gold retailers, suppliers and traders. SAO’s hallmarking is a voluntary scheme where manufacturers, traders, and retailers of gold jewellery submit their jewellery pieces for assaying and hallmarking. The scheme facilitates two procedures: testing and hallmarking.   

SAO is SAC Singlas Accredited (Singapore Accreditation Council - Singapore Laboratory Accreditation Scheme) and is also recognized by the London Bullion Market Association – an honour accorded only to establishments that have attained the highest level of assaying expertise. 

SAO is Singapore's only recognised and independent body that tests and certifies precious metal articles.


Testing Process  

X-Ray Fluorescence Material Analysis (XRF) - a non-destructive material analytical method to determine the homogeneity of a batch of articles. In this process, a sample is irradiated with X-rays from a controlled X-ray tube. The X-ray emission penetrates only the surface of the sample to determine the elemental composition of the metal. 

Fire Assay - This is done after XRF as it is a destructive method. The sample is weighed, and then placed in a high-temperature furnace for oxidation to remove base metals, a process known as cupellation. The molten globe consisting of gold/silver is then treated with nitric acid after cooling to separate silver from gold. The gold sample is then weighed to determine its purity. 


If the samples in a batch being tested meet industry standards, SAO will hallmark every piece of the jewellery in the batch with a SAO mark (lion’s head in a diamond shape) to certify its purity. The hallmarks may be lasered or stamped on. The complete set of hallmarks consists of the SAO mark, the standard mark and the jeweller’s mark. 

Arthesdam Jewellery is proud to announce that all our gold jewellery is certified by the Singapore Assay Office (SAO) with the SAO Hallmark, the only assurance of gold authenticity in Singapore.