Diamond colour

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.

Colour is important because it affects the transparency of the diamond and whether it has a yellow tint. So for example, if you choose a D colour, it will be colourless whilst a K colour diamond will have a hint of pale yellow. However, in a round brilliant diamond, provided you choose a colour that is H or above, it is the cut grade that makes a diamond look beautiful.

Compare these two diamonds - they are both perfectly cut diamonds with superb Hearts & Arrows. The only difference in specification is that one is a D colour and one is H colour. In this image, we are comparing the light return of the two diamonds. Both have excellent light return and excellent contrast pattern.

Comparing the levels of light refraction between the two diamonds, both have very attractive flashes of fire across the diamond. Both stones have similar levels of fire. In fact, it is very hard to pick the D colour from the H colour when assessing which is more beautiful.

To see the difference between these two diamonds, we need to turn them face down against a white background. The H colour has a faint hint of yellow whereas the D is completely transparent. Choosing which colour to go for then comes down to personal choice; if you want a better colour, it will be rarer and will therefore cost a little more.

In order to make sure that your diamond is as beautiful as possible, you should look for a perfectly cut Hearts and Arrows diamond. Provided you have chosen a stone from the near colourless range (H or higher), you will not notice any traces of yellow within your diamond.

Description

Whether you are looking to learn a bit more about diamonds or you would like to become more of an expert, our diamond videos and diamond guides are made just for you. In this video, we explain 'diamond cut' and why it is so important to how beautiful the diamond looks.

Video Transcript

In some cases, a diamond can be made too shallow. Again this means that the angles are less than optimal, so light leaks through the bottom of the stone. A round brilliant diamond is given a cut grade by the major grading labs like GIA, IGI and HRD. These grades are Poor, Fair, Good, Very Good, Excellent.

The cut grade gives you a good starting point guide but it is worth knowing that each grade involves a range of quality, so two diamonds which for example are both Excellent Cut will often have differing levels of optical performance.

Here is a comparison between a GIA "good cut" and one of our Hearts and Arrows diamonds which has been graded Excellent cut by GIA. You are looking to see which stone has more flashes of refracted colour as it moves through the light - this is what you will see when you view the diamond in direct sunlight or office lighting.

Comparing the brightness of the two diamonds, the hearts and arrows has a lot more white light return and so looks the brighter diamond with better contrast pattern. The differences you are seeing are down to the quality of cut of the stone. When you are choosing a diamond, if you want it to be a beautiful as possible, it is important to choose the very cut possible.