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To complement its hallmarking services, the Goldsmiths’ Company Assay Office London now offers a GEM TESTING SERVICE. In conjunction with The Gemmological Association and Gem Testing Laboratory of Great Britain (Gem-A), the longest established gem testing laboratory in the world, we will provide a wide range of gem testing services including diamond grading, gem identification, pearl testing and opinions on heat treatment. A One-Stop-Shop for Jewellery Services The Goldsmiths’ Company Assay Office London is where hallmarking began 700 years ago. Integrity, quality and service have been at the core of its success since it started and it is constantly developing its service portfolio to meet the needs of its customers. Gem Testing The wonderful variety of gemstones on the market today provides increasing choice for your customers but also presents you with the challenge of accurately identifying them, and recognising the various imitations and treatments that can catch out the unwary. Today's good-practice guidelines also require you to be open and truthful about pricing and durability features that may be affected by treatments.

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Many jewellers employ qualified gemmologists but, even then, confirming the identity of gemstones and recognising some of the latest synthetics and treatments requires access to equipment, expertise and experience found in a professional gemmological laboratory. We can now offer this service.

Diamond Grading
Diamond Grading Reports have become a common and invaluable feature of the modern jewellery trade.

Our Diamond Grading Reports follow the universally recognised GIA colour and clarity grading systems, while also providing cut assessments. GIA cut grades for round brilliants can be supplied on request.

Buy and sell with confidence with one of our Diamond Grading Reports.

* The heat treatment of rubies and sapphires is a long-established and common practice. Opinions on heat treatment are subjective ones and usually based on minute internal features and other characteristics of the gem. It is not always possible to provide such opinions and when they are provided they are for guidance only. Such opinions can vary from expert to expert and no warranty is implied. ** The treatment of fresh and sea water pearls is becoming increasingly prevalent. Our report will note whether any treatment has been observed. Such opinions can vary from expert to expert and no warranty is implied.

How To Get Gems Tested
In order to get gems tested or diamonds graded you will need to complete a gem testing hallnote and submit it with the stone or stones to be tested. You will find a supply of hallnotes in our pack. To obtain a pack or for further advice on any of our services, please email gemtesting@assayofficelondon.co.uk or telephone 020 7606 8971.

Articles should be packaged appropriately to prevent damage. The hallnote relating to each packet should be readily available when the packet is opened. Packets can be sent by courier or post, or brought by hand to the Assay Office counter. The counter is open Monday-Friday, 8.00am–5.00pm. It is closed on Bank Holidays.