COLOUR

When we speak of Colour in a diamond, we actually mean the degree of colourlessness. While most diamonds are white, not all are truly colourless. Many are tinted yellow to brown or silver to grey.

In a white diamond, the presence of a tint is considered undesirable. This colour impurity is caused by lingering traces of nitrogen, boron, hydrogen or other elements. Commonly, diamonds are affected solely by nitrogen traces, which create pale yellowish or brownish tints. Only diamonds composed of 100% pure carbon without any impurities may be completely colourless.

Diamonds are graded on a Whiteness scale or absence of colour scale. Basically, the whiter or clearer the colour of a diamond the greater its value.

Grading

The Gemological Institute of America (GIA) has devised a set of guidelines to grade diamond colour. The colour of graded diamonds is compared to that of control stones, which are preselected gems of a specific colour.

To be graded, diamonds must be loose stones, because once a diamond is set into metal the metal can affect its colour. Diamonds are placed table-down, pavilion-up and viewed with a 10X loupe under controlled lighting and precise viewing conditions. A lettering system from D to Z is used to identify the amount of colour present in each diamond, with D awarded only to rare, totally colourless diamonds. Many of these colour distinctions are so subtle that they are invisible to the untrained eye. But these slight differences make a very big difference in diamond quality and price.

Why does the GIA colour grading system start at D?

Before GIA developed the D-Z Colour Grading Scale, a variety of other systems were loosely applied. These included letters of the alphabet (A, B and C, with multiple A’s for the best stones), Arabic (0, 1, 2, 3) and Roman (I, II, III) numerals and descriptions such as "gem blue" or "blue white." The result of all these grading systems was inconsistency and inaccuracy. Because the creators of the GIA Colour Scale wanted to start fresh, without any association with earlier systems, they chose to start with the letter D—a letter grade normally not associated with top quality.

Fancy Coloured Diamonds

A few diamonds are exceptions and do not fall into the colour category set by GIA. They are referred to as the fancy coloured diamonds. The well-defined colours include pink, canary yellow, blue and green. Some are quite rare and hence expensive.

In a fancy colour diamond, intensity and hue of colour plays the most important role in deciding value. If a diamond has very intense colour and is rarely found, it can even be more expensive than colourless or white diamond.

Fancy yellow or brown diamonds are commonly available, so they are priced relatively less than colourless diamonds. On the other hand, pink, red, blue and green are very rare, and are valued more than colourless diamonds.

The intensity grading system for fancy colour diamonds differs than that of white diamonds. Unlike white diamonds, which range from the letter D-Z, fancy colour diamonds are graded by Light, Fancy Light, Fancy, Fancy Intense, Fancy Deep, Fancy Dark, and Fancy Vivid.

Fluorescence

Fluorescence is another factor that can affect diamond colour.

This is an effect that is seen in some gem-quality diamonds when they are exposed to long-wave ultraviolet light (such as the lighting frequently seen in dance clubs). Under most lighting conditions, this fluorescence is not detectable to the eye. Since UV radiation is a component of daylight and is also present in fluorescent lit rooms, diamonds with this characteristic can appear to change colour quite often. While most gemologists prefer diamonds without this effect, some people enjoy it. It's really just a matter of aesthetics.

Strong blue fluorescence can make a yellow coloured diamond appear more white, but in rare cases can cause a stone to appear milky or oily. This milky or oily effect is called an "over blue" and only applies to a small number of "strong" and "very strong" fluorescent stones. Stones that fluoresce yellow appear even more yellow under some lighting conditions.

It is common to find that diamonds with colourless grades (D-E-F) or near colourless grades (G-H-I-J) are lower in price when they exhibit fluorescence and faint yellow grades (K-L-M) are higher in price when exhibiting fluorescence.

What Colour Diamond Should I Choose?

The difference in appearance between colourless diamonds and near colourless diamonds may not be detectable, but the price difference from one colour grade to another can be significant. The purists at heart will always demand diamonds in the D-F range. By selecting diamonds in the G-I range, however, you can find a tremendous value while still achieving a "colourless" look.  

If you find that you are sensitive to low colour grades, then we suggest you choose a diamond with the colour grade that satisfies you. However, if you have difficulty differentiating between different colour grades, then you may want to consider a nearly colourless diamond.

Some experts suggest getting a diamond that has a small amount of colour, which will soften the light and make it easier to view the entire spectrum of colour that is given off when the diamond scintillates.

If you are looking for a round brilliant diamond, you have a bit more flexibility in your colour grade, because the brilliance makes it more difficult to detect colour. In this instance, anything over I colour is usually more than adequate, and will appear completely colourless to the untrained eye unless held up against a diamond that is at least 3 colour grades above it, such as an F or E colour diamond.

Diamonds with pointed ends, specifically marquis, radiants, trillion, pear and sometimes even princess shaped diamonds tend to focus the colour on these points. In this case, it is usually best to stay with a colour grade of H and higher. However, if you have a pronged setting, the prongs will usually hide this colour concentration

In addition, when you are looking for multiple stones, such as loose diamonds for a 3-stone ring, it is important to make sure that the colour ranges are at least within 1 grade of each other.

If you are shopping on a budget or trying to maximize the size of your stone, then "J" diamonds are most affordable and still near colourless. You may also want to consider choosing a diamond with medium or strong fluorescence. Since these diamonds are discounted slightly in price you can often afford a higher colour stone without paying the premium.

Tips

• As diamond size increases, colour becomes more noticeable. This is especially important to keep in mind if purchasing a diamond of two carats or greater.
• The visible difference between diamonds of one colour grade, for example G to H or I to J, is so minor it is difficult to detect with the unaided eye. The cost savings, however, can be significant.
• Diamond shapes that reflect more light (i.e. have more sparkle), such as round or princess, can mask some colour in a diamond.
• The type of metal in which a diamond is set can complement its colour. Consider setting diamonds graded I or J in yellow gold. White gold or platinum best complement diamonds with a colour grade of D through H.