When it comes to grading a diamond’s colour, we are quite familiar with the D to Z scale with D being colourless and Z being intensely coloured, usually yellow. And of course, the better the colour grade (D), the more expensive it is. However, what happens when a diamond exhibits colours beyond the Z range, or scintillates colours other than yellow? It then follows an opposite rule that the more intense the colour, the more expensive it is. Coloured diamonds follow their own colour scale of fancy light, fancy, fancy intense, fancy dark, fancy deep and fancy vivid.
Natural coloured diamonds are some of the most exorbitantly priced items in the world, with many prime examples selling for amounts many of us will take several lifetimes to earn. For example, the most expensive diamond is a 59.6ct oval pink diamond known as the “Pink Star” which sold for a whooping $71,000,000 (for those who are blinded by the number of zeroes, that is $71 million). The good news is that you can also get coloured lab grown diamonds which are much much more affordable than natural ones, which The Better Diamond has a large inventory of.
Coloured diamonds come in a variety of colours - yellow, pink, orange, red, blue, green, purple, brown, black and even white. In its naturally occurring state, the rarest colours are red, green, purple, and orange. Pink and blue coloured diamonds are next in line, followed by yellow and brown diamonds being the most common. Many of the fancy coloured diamonds are also a blend of colours such as pinkish orange, greenish yellow, purplish pink etc. These mixed colours are usually more affordable than their pure coloured counterparts.
A diamond’s colour usually stems from the impurities present in the diamond’s carbon crystal structure. However some of the fancy coloured diamonds are actually pure carbon with no impurities. Diamond colours can also be enhanced through treating methods such as irradiation and high pressure high temperature. Below are some of the colours and how they come about.
The 2nd most common naturally occurring colour, yellow, is the result of nitrogen impurities attaching to the diamond during formation. The higher the concentration of nitrogen present, the more intense the colour. The most intense yellow diamonds are also referred to as Canary Diamonds. The most common colour is brown which is the result of nitrogen impurities and irradiation.
Blue diamonds result from boron impurities trapped in the diamond. As boron only has 3 electrons for bonding, one of its adjacent carbon atoms will have an unused electron which absorbs red light, resulting in a blue tint when white light passes through. The intensity of its blue colour will also be correlated with the concentration of boron present.
The green colour is derived from exposure to radiation, which can occur naturally or treated in a lab. Naturally, the diamond would be exposed to uranium radiation from rocks near the earth’s surface. Green diamonds can only be sold after their radioactivity falls below the level that is safe for manufacture and sale to the public.
On top of creating green lab grown diamonds through radiation, a green diamond can also be grown through combining nitrogen and boron into the diamond, just as the colours yellow and blue would make green.
The purple colour arises from hydrogen and boron impurities found within the crystal structure of the diamond. The higher the concentration of these two elements, the more intense the purple. Naturally occurring purple diamonds are amongst some of the rarest diamonds in the world.
A naturally occurring pink diamond is extremely rare, and in fact, the exact cause of a diamond’s pink hue is still unknown; all we know is that nitrogen and other impurities are not the cause of the pink colour. The common theories attribute the colour to a distortion in their crystal structure, possibly due to enormous additional pressure during the formation. The rarest pink diamonds can sell for over $2 million per carat!
The plastic deformation of a pink diamond’s structure is currently not replicable in any laboratory treatment or growth process. Therefore, to create a pink lab grown diamond, you would take a lab grown diamond grown in nitrogen impurities and expose it to radiation, then subject it to temperatures of 600-1000˚C.
Red diamonds are the rarest coloured diamonds as there are fewer than 30 known true red diamonds in existence. Like pink diamonds, the source of their colour is still unknown but is also likely attributed to their irregular structure, resulting in a ruby colour as light bends through it. They are in fact pure carbon diamonds just like a colourless D coloured diamond. Due to their rarity, even diamonds under 1 carat can be considered investment grade, and most go for about $1 million per carat. The largest red diamond is the Moussaieff Red Diamond weighing 5.11 carats and has an internally flawless clarity.
A red lab grown diamond too can be achieved through post growth irradiation to alter the crystal lattice structure of the diamond, and then heated after to achieve its red colour.
Black diamonds are perhaps one of the least popular fancy coloured diamonds. They are the opposite of your brilliant colourless diamond as they absorb light. The black colour comes from graphite inclusions randomly clustered throughout the diamond, impeding any dispersion of light.
As black diamonds are not priced very high to start with, we have not seen many examples of lab grown black diamonds because their value does not justify the cost of production.
Not to be confused with colourless, a white diamond gives off a white milky appearance due to sub-microscopic inclusions which causes light to be scattered as it passes through. Its colour is reminiscent of white opal and is often described as “opalescent”.
With the invention of lab grown diamonds, rare fancy coloured diamonds are no longer out of question when it comes to designing your very own custom jewellery. While fancy coloured lab grown diamonds do tend to cost more than their colourless counterparts, they are however still much more affordable than naturally coloured diamonds. If you are fascinated by fancy coloured diamonds and would like to find out more, feel free to reach out to any of our consultants and we would love to talk it through with you.