• Have you ever wondered why grading a diamond colour starts with the letter ‘D’? Wonder no more.

Have you ever wondered why grading a diamond colour starts with the letter ‘D’? Wonder no more.

Just recently, the President of the London Diamond Bourse, Mr Harry Levy, gave an interview to the World Diamond Magazine. In it he recalls how grading came about. Now being in the industry for coming on 25 years, I often get asked why the grading a diamond starts at the letter 'D' and not 'A'. I'm pleased to say that I give the same answer as Harry. Below is an extract from that article for you to enjoy.

"Gemological laboratories were first set up as places to identify gemstones of natural origin. These early laboratories were set up in most jewellery-producing centres, but were run through other bodies. This was because there was little funding available so they needed subsidizing, and most importantly they had to be commercially independent to prevent fraudulent results. In the UK a laboratory was set up in Hatton Garden, London, and run by the London Chamber of Commerce.

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Research had to be done in developing the methods of detection, so the laboratories were run by people with a scientific background, and this led them to become educational institutions trying to teach traders (and anyone else that was interested) the basics and, later on, more advanced gemmological knowledge. Identification, research and education were their most important aspects until the grading of diamonds became necessary.

Initially diamonds were not graded to determine their value but as a method of communication. Traders had developed local ’languages’ using descriptive terms such as ’white’, ’yellow tints’, ’light PK’ (pique), ’small inclusions’ and so on. This worked in localities where traders were in daily contact with each other and could compare goods, thus allowing them to ascertain prices and so be able to trade. However, this only worked in closed communities - each locality developed its own terminology. The most common were descriptive terms, but others used localities where the diamonds were found.


One such system is the Scandinavian Diamond Nomenclature (Scan.D.N), which uses terms such as ’River’, ’Wesselton’, ’Crystal’, ’Cape’ and ’Yellow’. Once you are involved in international trading, a system that all can understand and use is needed. Around the early 1950s the GIA developed its colour-grading system, using letters to denote colour. This is achieved through a series of "master stones," where each stone is perceptibly different from the previous one. The GIA decided to name the top stone (the one showing no colour) "D" and then graded them down to "Z." The colour of a diamond is then determined by comparing it to the master stones.

If the colour falls between a G and H for example, it will be classed as G, although some systems would grade such a stone as H. There is no confusion as the master stones are so named to adjust for this apparent discrepancy. Thus in the second system just mentioned the H master stone would be a G using the first system. These games have been played between laboratories for years to show that each is using an independent system from the others.

The letter ’D’ was selected by the GIA as the highest colour grade as this was the failure grade in American school exams. At that time the top colour was referred to as either ’A’, ’A++’, ’A+++’, ’Super A’, or similar terms by the traders in the market. D was a colour that was never used, so the GIA used this as the top grade knowing that nobody else had used this letter - this was recounted to me by Richard Liddicoat.


The clarity grade was adopted by all, using the descriptive terms such as ’flawless’, ’very very small inclusions’ (VVS), ’small inclusions’ (VS), ’slight inclusions’ (SI) and so on. Exactly where and how the divisions occurred in the different systems is not exactly clear.

Having established a system to grade for colour and clarity, the carat weight was always a given, and the cut was also listed as a descriptive term, and so the 4Cs as a means to determine the value of a stone became available."

Harry Levy

Harry Levy is among the diamonds, gem and jewellery industry's most treasured and veteran public servants.

He is, among others, President of the London Diamond Bourse; President of the Gemological Association of Great Britain and Chairman of the International Diamond Council.

If you would like an appointment, then please do call for a free consultation in our central London Hatton Garden office and we would be glad to try and help you. Our details are on the main page of the Lewis Malka London website.

Lewis Malka is a recognised expert in making diamond rings as well as being a famous jeweller to the stars. All his blogs are his own opinions. He is a member of the London Diamond Bourse (LDB) and also sits on the board within the Diamond Bourse. You can follow him daily on Facebook, Twitter and Instagram. If you would like any bespoke jewellery made, then please visit his website.

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