How diamond colour affects the appearance of a diamond

Colour is not a measure of the quality of a diamond, but rather it's rarity. In white diamonds, the better the colour grade the more rare the diamond. Diamond colour is caused by chemical impurities. For example, nitrogen will cause a yellow tint to the stone.

There have been diamond colour-grading systems since the early 1700s. But today, we use the standard that the GIA or Gemological Institute of America invented and developed in the 1950s. This scale starts with D and continues with increasing presence of colour to Z.

D colour diamonds are completely colourless and are the rarest and most chemically pure. Z colour diamonds are light yellow or brown and will usually sell for a much lower price. When a diamond is being graded for its colour, it is given to a gemologist with a master set of stones to compare with the diamond that they are grading.

The diamond is positioned face down, rather than face up so that the gemologist can evaluate the body colour without it being obscured by the brilliance of the diamond.

Some shapes of diamond, like the emerald cut, show up colour differences a little more due to the nature of the facet arrangement. This is evident in the face up position if the stones are examined carefully.

There is a degree of variance within each colour grade that can make a difference to the appearance of a diamond. The image on the left shows two G colour diamonds. They are both GIA certified as being G colour. However, the stone on the right is not quite as clear or white as the stone on the left.

As with all of the four C's, diamond colour is subjective. What may be right for one person may not be right for you. Some people find that lower grades, like J or K, are preferable as it adds a certain warmth to the stone, whilst others prefer higher colour grades for their purity.