All about certificates…

Posted June 26, 2014


Over the last decade or so it has become customary to provide certificates for precious gemstones.  But there is some confusion over what the certificates actually are, and so in this blog I aim to try to clarify some of the issues.

Certificates are produced by independent laboratories, staffed by experienced and highly qualified gemmologists who carefully examine and analyse all the attributes of a precious stone.  They will confirm the identity of the stone, the colour, clarity, carat weight and cut.  They will check the natural and untreated rarety of each stone, the gemmological structure and can sometimes identify the country – even the mine – of origin.  They will test the stone using powerful microscopes and other specialist instruments to detect any sign of synthetic, treatments such as cavity drilling and filling, oiling,or dyeing, surface coating or any processes that might have been used to enhance the colour of the gem.  They will measure and weigh the stone, test for specific gravity, the refractive index and how the stone absorbs  and reflects light.

They will then provide a very detailed report that is numbered and traceable.  The certificate provides a wealth of detailed information for insurance valuers, workshops, retailers, consumers and anyone who needs to understand and work with that gemstone.

Certificates are issued only to gemstones that are natural and untreated and over about 0.30cts in weight.  However, some laboratories will issue certificates for coloured gemstones that have been enhanced, listing the specific treatments; others will supply special certificates for synthetic diamonds.   The value of the certificate in these cases is that it identifies the gemstone and the customer knows exactly what they are buying.  The job of the laboratory is to identify the stones, not to value it.  That is the job of the valuer, gemmologist or gemstone dealer.

So is it necessary to have a certificate for a precious gemstone?  Not strictly necessary but it is advisable if you are purchasing the stone from anywhere outside the UK.  But make sure the certificate is both genuine and from a reputable international laboratory.

The leading gemstone laboratories of international repute are :

GIA: the Gemological Institute of America

IGI:  International Gemological Institute

HRD:  HRD Antwerp Institute of Gemmology

But the laboratories only offer an opinion based on their knowledge and expertise and no-one is infallible – the science of gemmology is not an exact one and as technology improves we learn more about the mysteries of gemstones every day.  For further information about the Gem Laboratories, look at the web site for The Laboratory Manual Harmonisation Committee (LMHC) whose members are subject to considerable scrutiny and who share information and research with others in the group.  All the members endeavour to be consistent in their reporting procedures.

And finally, if in doubt, the UK has in place laws to protect consumers from traders to try to mis-describe a gemstone.  It is called the Consumer Protection Act and anyone who falls foul of it can be sued under both civil and criminal law. It is operated by the local Trading Standards Officer who can advise consumers on how to deal with a problem if it should arise.

Probably the most important piece of advice that we at hattongarden.com can offer you is to buy from a reputable jeweller – go and see them, talk to them and learn about this fascinating subject.  That way, you can be sure that you understand exactly what you are buying.

For more information on the treatments that are sometimes given to gemstones, look at the education section of the GIA web site: http://www.gia.edu/gem-treatment.  

For more information about The Laboratory Manual Harmonisation Committee: www.lmhc-gemology.org/About_the_LMHC.html.    

For more information about the Consumer Protection Act: www.tradingstandards.gov.uk