Why does the diamond color grading start at D? What about A, B and C?

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People often wonder why the color grading scale starts at D and not A. The answer to this is really quite simple. There was a time when the color scale actually started at A. In addition to starting at A, color systems were also assigned numbers (0, 1, 2,3), Roman numerals (I, II, III), and even (AA) . Classifications such as “gem blue”, “fine white”, or “bluish white” were used as color descriptions. These color grading systems were loosely applied and often inaccurate and inconsistent. Early on when the diamond trade developed, various parties within the trade developed diamond grades. These original scales never included the letter D and when the Gemological Institute of America (GIA) created the new scale in 1953, they decided to start over with a letter that was not part of the previous grading system.

The GIA scale is now the official color grading scale and is universally accepted among laboratories and dealers. This current scale runs from D to Z, with D being colorless to Z, which is light yellow or brown. The term color in regards to diamonds actually refers to their lack of color and the less color a diamond has, the rarer and more valuable it is. Brown or yellow diamonds that are deeper in color than Z on the grading scale are considered “fancy colors.” These diamonds are graded by a completely separate system and this same system is normally used to grade colored gemstones such as rubies, sapphires and emeralds.

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