Many years ago, when the diamond trade had just begun to develop, The London Diamond Syndicate was in the business of sorting rough diamonds that it intended to sell to the public. Because there was no industry-wide standard at the time, different diamond grades were assigned by various organizations. Random scales were created that included numbers, letters, and even Roman numerals. It became common practice to sell diamonds as Triple A. Other classifications were given including river, jagers, gem blue, and fine white; however inconsistencies within the industry led to the establishment of a new grading system in 1953.
So, why does the Diamond color scale start at D? In an effort to create a comprehensive system of grading diamonds, The Gemological Institute of America (GIA) developed a more widely accepted grading scale that classified the gem by letter grades. It desired to move away from the arbitrary methods of rating developed in the past, to establishing a more standardized color-grading scale that ranged from D to Z.
While diamonds are generally considered colorless, they can also run the gamete of tones and hues - from light yellow and brown to greenish-blue and reddish-orange.
The answer to the question “why does the diamond scale start at D” has a lot to do with the amount of color displayed within the body of the gem. Diamonds considered to be completely colorless, fall at the beginning of the scale and are assigned a D grade. Those that display a slightly yellow or brownish hue are placed at the end of the scale and are given a grade of Z. A stone with a high amount of body color is considered a lower grade than one with a smaller amount of color. The rarest of all diamonds are the ones that have no color at all but rank the highest on the scale.
A diamond’s color can also make all the difference in how valuable or invaluable it is. If a white diamond has a slightly yellowish hue, it is offered at a more discounted price than it would otherwise be if it had less color.
In the industry, colored diamonds are referred to as Fancy diamonds (or Fancy-colored diamonds). These gems are subject to a completely different grading system than white diamonds. This separate classification was developed because the color saturation of diamonds doesn’t stop at Z: it actually continues to increase. In fact, diamonds are discovered in every color of the rainbow and the deeper the hue, the more valuable it becomes.
Fancy-colored diamonds graded on this separate scale begin at Fancy Light and end at Fancy Vivid. Rare colored gems are more expensive than their more commonly colored counterparts. The rarest and most expensive diamonds are actually found at the opposite ends of each respective grade scale.
While many people today might ask “why does the diamond scale start at D”, it may be worthwhile to peel back a bit of history. There, you might be surprised to discover that many years ago, the diamond color-grading scale never really started at D - but that it, essentially, all began at Triple A.