How To Buy Diamonds

How to choose Fancy Colour Diamonds.

Anyone who has ever taken an interest in purchasing diamonds has undoubtedly been lectured on the importance of the diamond Cut, Clarity, Colour and Carat weight, known colloquially as The 4 C’s.

Whilst most consumers traditionally look for clear, colourless diamonds, there is a growing interest and demand for buying Fancy Colour Diamonds. The ‘4 C’s’ are equally relevant to buying Fancy colours, but with the emphasis on colour. The following information may offer some insight into the rudiments of colour grading and can be used as a general guide when looking at fancy colour diamonds.  

Laboratory Certificates:

The primary purpose of sending any diamond to a Gem Laboratory is to ensure that it is Natural. Natural diamonds are those which have been tested with laboratory equipment and verified to be free of artificial enhancements that alter diamond purity or colour. Once established as natural, laboratories proceed to grade diamonds according to their level of colour and purity. Colour and purity are the two main elements, which determine a diamond’s value on the market. The better the colour and purity, the greater its commercial value.

Colour Grading:

Colourless diamonds are graded according to an alphabetic scale. The highest, most desirable colour at the top of this scale is D colour. A D colour diamond will be judged to have the clearest possible translucence, whereas diamonds of a lesser transparency are graded further down the scale - E, F, G, all the way to Y-Z (Light Yellow). Diamonds with high colours (i.e. very transparent, without any tint or hue) are more valuable than diamonds where colour is present. Whilst one can clearly see a difference in colour between a K color diamond and an F, most people would have great difficulty differentiating between F and E colours, with the naked eye.

Similarly, Fancy Colour diamonds are graded according to diamond colour but the grading scale works in the reverse – the stronger the colour, the more valuable the diamond.

Fancy colour grading begins with a Faint grade that suggests that the diamond colour is indeed faint. The next color level up is Very Light, then Natural Light, Fancy Light, Fancy, Fancy Intense and Fancy Vivid, which is the ultimate colour grade. In between Fancy Intense and Fancy Vivid, are the grades Fancy Deep and Fancy Dark. Fancy deep colours are more ‘syrupy’ and less clean than intense or vivid colours but they still possess lustre and are pleasant. Fancy dark however, indicates that the colour is oversaturated and lacking vibrancy, making the stone appear, well, dark.

Purity Grading:

All diamonds share the same guidelines for purity grading. Due to their chemical composition, diamonds possess natural impurities. These impurities sometimes manifest as black carbon spots, clear (gas) bubbles or graining lines, which are commercially labeled as ‘birthmarks’ because they are inherent to the crystal. Other impurities, such as cracks and chips may have evolved in a diamond through the mining or polishing processes.

Diamonds that are absolutely clean and free of any inclusions are certified IF, or Internally Flawless. From this point, the scale descends according to purity. Should a diamond have a very, very small inclusion that is traceable when observed under a microscope, it will be graded a VVS1 (an acronym for very, very small). Should a diamond have a slightly larger inclusion that is traceable when observed under a microscope, it will be graded VVS2. Predictably, the scale changes as inclusions become larger and more noticeable. Should a diamond have a very small inclusion that is traceable when looking through a handheld diamond magnification loupe, it is graded Very Small - VS1 or VS2; and if the inclusion is slightly bigger it is graded as Slightly Included - SI1 or SI2.  Diamonds with inclusions that can be seen with the naked eye, are graded as Included - I1, I2 and I3.

Fracture Filled Diamonds:

When rough diamond crystals are removed from the earth, they are seldom perfect. Notwithstanding the millennia of pressure under which they have been formed, the industrial processes of diamond mining and polishing can sometimes cause stones to chip or crack. Over time, various treatments have evolved to improve the appearances of cracked diamonds. One popular treatment is called fracture filling, whereby a transparent silica composite literally fills the diamond crack, making it less obvious to the eye. Stones, which have undergone this type of treatment are less expensive but once treated can look as good as any diamond. Laboratory certificates for these types of diamonds indicate that the diamond is ‘Fracture Filled’.

Colours & Hues:

Fancy Colour diamonds are graded and certified according to their primary colour. This colour is the last or only colour specified in the colour category, of a laboratory certificate. For example, a Fancy Yellow certificate confirms that the diamond colour is definitively yellow in colour; a Fancy Pink certificate confirms that the diamond colour is definitively pink, etc.

However, fancy colours often have a secondary colour. This secondary colour indicates that a hue is present in the primary colour. For example, Fancy Greenish Yellow indicates that the overall yellow colour of the diamond has a greenish tint. Furthermore, the wording of the colour category establishes the degree to which this hue influences the overall diamond colour. Should the colour category read Fancy Purplish Pink, we infer that that 35% of the overall (pink) colour is purple. A certificate grading of Fancy Purple Pink, indicates that 50% of the overall colour is purple. Some hues are exclusive to certain colours and others are common to more than one colour. For example, greenish hues are common to yellows, blues and greys, whereas brownish hues are common to pinks, yellows and oranges. Purplish hues are common to pinks and reds and orange hues are common to browns, yellows and pinks. Hues, such as brown in particular, are less desirable because they have a tendency to darken and diminish primary colours. Consequently, diamonds with brownish hues fetch lower prices.

The primary diamond Colour and the rarity of a particular colour is central to establishing the market price of fancy colour diamonds. Some fancy colours such as red, violet, orange and purple are so scarce that they are unaffordable to almost everyone. Yellows and browns on the other hand, are relatively abundant and affordable. Blues pinks and greens are also rare diamond colours, but they are in strong market demand and bought at a premium. Ultimately, certified diamonds with a distinct, single colour fetch higher prices than those with secondary hues.   


Some diamonds display fluorescence because of the diamond crystal’s proximity to natural radiation found in the earth. It is important to note that this radiation is completely harmless and does not affect our physical well-being.

One can see diamond fluorescence under a UV light and it is usually blue but it can also be yellow or white. The strength and colour of fluorescence affects the tonality of the diamond and in some cases, very strong fluorescence causes diamonds to change colour temporarily. Diamonds that change colour temporarily are known as “Chameleon” diamonds. Chameleons are usually a brownish-greenish color and have strong yellow fluorescence.

Buyers of ‘white’, colourless diamonds avoid fluorescence because it potentially affects the opacity of diamonds as well as causing a secondary hue in the colour. In reality however, unless a diamond has medium or strong fluorescence, it is unlikely that the average person will spot a fluorescent diamond.

The threshold of tolerance for fluorescence in fancy colours is generally greater than with colourless diamonds, although this too depends on the hue generated by fluorescence. It is worth noting however, that fluorescence can sometimes enhance intensity in fancy colours and it is vital for colour change in Chameleon diamonds.

Undetermined Colours:

If a laboratory grades a fancy colour diamond as ‘Undetermined’, it is implying that it cannot verify if the diamond colour is natural or artificially enhanced. On the one hand, natural radiation under the earth’s surface configures diamond colour and is common. On the other hand, colour treatments do exist whereby diamonds are ‘bombarded’ with artificial radiation to improve colour. The confusion arises when natural radiation appears at levels, which laboratories suspect might be artificially enhanced, but cannot positively identify the source of radiation because other gemmological factors in the diamond are normal. This lack of clarity brings dealers and laboratories into direct conflict because undetermined diamonds are sold for considerably less money than equivalent stones with a natural colour grading.

Dealers and Laboratories:

It may be impolitic to say this openly, but colour diamond grading is a constant source of tension between the Gem testing Laboratories and diamond dealers and manufacturers.  

Dealers and manufacturers speculate on fancy colours according to the colours they see. They inspect diamonds in ordinary, everyday conditions which are almost identical to the environment in which they expect the diamonds to be worn when set into jewelry. Trading experience automatically provides dealers and manufacturers with a sense of the value of stones, which naturally guides them towards some stones and away from others. This trained intuition gives dealers a not unreasonable basis upon which to asses colour correctly, and they will undoubtedly have plenty of laboratory certified stones with colour grades to support this assumption.

A lab technician on the other hand will be looking at the stone unaware of its commercial value. Using sophisticated equipment, technicians follow scientific procedures to establish colour grading. Unlike the dealer who sees the colour as a sum of all its parts, the technician will disassemble the colour and will likely identify a secondary colour, or hue. Where dealers or manufacturers see a diamond  as ‘straight’ pink, the laboratory technician will grade the same diamond ‘purplish pink’, or ‘brownish pink’. By doing so, the stone can potentially lose up to 20% of its value, which will motivate almost anyone to challenge the laboratory grading. Needless to say these challenges intensify when the stones are potentially more valuable.  

Which laboratory?

There are a number of gem testing laboratories that issue diamond grading certificates. The most prominent of these laboratories is the Gemmological Institute of America, also known as GIA. The GIA is known for its advanced facilities and grading methods and is probably the one laboratory whose standards are accepted universally. Other well-known laboratories are the International Gemmological Institute and HRD. International Gemmological Institute, also known as IGI is based in Antwerp but has a broad international network of laboratories. HRD is another Antwerp based laboratory, which also boasts overseas representation. Interestingly, whilst all laboratories allege to offer the ultimate testing services, all are prone to inconsistencies and mistakes. If there is one consistency however, it is in the knowledge that were you to submit one stone to each laboratory separately, you will receive three different colour and purity grades on the same stone.  

Finally, How To Choose Your Diamond?:

The most elementary rule for choosing a diamond is to go for the stone that you like. Too often people become over-involved with the details on certificates and forget to actually look at the diamonds themselves. Furthermore, diamonds do not always conform to the data established by microscopes and spectrometers and very often a Gem Laboratory’s “Fancy Brownish Orangey Pink” is everyone else’s ‘Pink’ diamond. Therefore, my best advice is for you to establish a budget and start looking at what looks good for you. If you like it, so will everyone else!