Consumers need to be aware that there are variations between different diamond labs when making a diamond purchase. Although many reputable jewellers offer uncertified diamonds with their own brand name or appraisal included, ideally a diamond should come with a grading report from a well known and reputable lab.
Most diamonds sold come with a diamond certificate or grading report which authenticate a diamond’s attributes. These reports will include features such as cut, shape, carat, colour, clarity, dimensions, etc.
There are many different diamond grading laboratories, but no across the board standards so different labs can produce different reports for the same stone.
Several renowned grading agencies in the United States and Europe have high reputations and different levels of standards:
- Gemological Institute of America (GIA): The foremost authority on diamonds. They set the standard for accuracy in grading diamonds particularly based on colour and clarity. Labs from all over the world commonly use GIA master set stones to compare colours and clarity grades when they’re uncertain on a grading.
- American Gemological Society (AGS): This lab sets the standard for precise measurements of cut parameters and carries out unrivalled detailed analytics to determine how close a diamond is cut to ideal proportions. Their colour grading is considered by some jewellers to be superior to the GIA’s. Pricescope found in a comparison of 16 cases, that 9 times out of 16 diamonds with AGS lab reports were better deals for buyers, mainly as a result of stricter clarity grades. In general AGS clarity grades were stricter than those given by GIA for the same 16 stones.
- European Gemological Laboratory (EGL): This lab is most popular in the US and has more labs around the world than any other. They have become renowned for providing fast, accurate and dependable grading which has given them a prominent place in the market. Pricescope found that EGL-USA colour grades were often softer than GIA lab grades but clarity grading was as strict or stricter. Unfortunately EGL-USA is in a legal dispute with EGL-International which has called their stringency of grading into question. When purchasing an EGL graded stone, be sure to insist upon EGL-USA or ensure that your jeweller is able to scrutinize the gem well.
- PGS (Professional Gemological Services): A far smaller lab yet well known for their accuracy and precise grading. They also offer light performance and other metric analysis which other labs do not. However, it is rare to find a PGS graded stone as they do not currently have much market share in the diamond industry.
- International Confederation of Jewellery, Silverware, Diamonds, Pearls, and Stones (CIBJO): Also known as the World Jewellery Confederation, an international confederation for these trade organisations now based in Switzerland and has representatives across the globe. Popular for development of the Blue Book, a three-part publication outlining terminology, classification, and ethical for coloured gemstones, diamonds and pearls.
- Diamond High Council (HRD, abbr. of the Dutch “Hoge Raad voor Diamant”): Respected Belgian institution based in Antwerp, a superior trading centre for rough and polished diamonds. HRD reports are more common throughout Europe and Asia.
- International Gemological Institute (IGI): The biggest lab by quantity and most IGI graded stones are sold in shops. Around for over 3 decades, it has become a trusted judge of excellence in fine jewellery evaluation.
Pricescope’s comparison between these labs found that all lab grades were in fact within a single grade of difference for colour or clarity tests, revealing that overall difference in laboratory opinion is marginal and that relative consistency is paramount in choosing a diamond.
If discover a diamond that is graded by a lab other than those recommended above, ensure you are diligent in researching the lab to determine if their grading is credible or not. It is sometimes wise to hire your own independent appraiser to verify their findings.
The key differences between the grading agencies are their diamond colour and clarity grading systems, which can prove somewhat difficult to compare against each other due to differences in scale. More and more agencies have made a move to standardize their grading scales with that of GIA. Therefore be careful with older certificates, as the grades may not match current ones (e.g. AGS amended its grading system in 1995). It is not advisable to buy diamonds with certificates that are more than three years old as they may not reflect the accumulated everyday wear and tear damage to the diamond.
The table below indicates the colour grading systems of four of the world’s most popular labs: GIA, AGS, CIBJO, and HRD.
Although some labs have a better reputation than others, grading is a subjective business and no lab can get it right on colour and clarity judgement 100% of the time. Any given stone can be graded differently even by the best labs. So remember to always scrutinize and compare every serious diamond purchase you intend to buy against other diamonds to determine if the grade is accurate.
Nearly all the major labs have an online confirmation system where you can check your gem and diamond purchases with their report number and weight.
GIA http://www2.gia.edu/reportcheck/index.cfm
AGS http://www.agslab.com/verify_diamond_grading_report.php
EGL-USA http://www.eglusa.com/customerlogin
EGL-World Wide
IGI
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