Diamond certifications are very important to determine the value of loose diamonds and to ensure you are getting what you paid for. But there is more than one grading agency around the world.
GIA (Gemological Institute of America)
GIA is the premier grading lab in the world and they invented the grading system currently in use today. They have a very high benchmark for colour and clarity and are known for their consistency and accuracy. GIA is also involved in research work, which ensures that they keep up to date on changing gemmological technologies.
AGS (American Gemological Society)
AGS has very strict guidelines for evaluating the cut of the diamond. Their thorough analysis of how close a diamond is cut to the ideal proportions and shape makes them very reliable. Their colour and clarity grades tend to be stricter than for GIA. They operate on a grading system completely different to the other labs, based on a number scale.
EGL (European Gemmological Laboratory)
EGL has two different companies, in dispute with each other: EGL USA and EGL International. While their clarity and cut grading are pretty stringent, they have a tendency to be lax in their grading of colour. This can lead to a diamond grade being off by two or three grades, affecting the price of the diamond. EGL USA is however more able to provide uniform assessment than EGL International.
HRD (Hoge Raad voor Diamant or Diamond High Council)
An Antwep-based gemmological laboratory, HRD is one of the major labs and is popular in Europe and Asia. Their colour and clarity grading are based on very high standards. They also have an anti-corruption policy in force where the owner of the diamond is not made known to the evaluators, thus preventing possible conflict of interests.
IGI (International Gemmological Institute)
One of the most popular laboratories in the world, IGI is also the largest gemmological lab in terms of sheer quantity of diamonds assessed every year. IGI has several franchisees and each one has their own standards. This can lead to disparities in the grading of an IGI certified diamond depending on which franchise evaluated it.
CIBJO (Confédération Internationale de la Bijouterie, Joaillerie, Orfèvrerie des Diamants, Perles et Pierres or World Jewellery Confederation)
CIBJO is not a lab itself but is an international federation of diamond trade organisations, which has put together some basic rules that any gemmological laboratory that wants to be recognised as genuine must follow. They are well known for their development of the Blue Book – a detailed guideline for classification and ethical trading of diamonds, gemstones, precious metals and pearls.
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