Colour
Fancy Coloured Diamonds
Most people hearing the word diamond picture a fine, colourless, sparkly stone in their mind. The fact is, diamonds come in all colours of the rainbow, and even in pink. Red, yellow, pink, blue, green, purple, steel gray and even black diamonds exist in addition to colourless. Most of them are significantly more rare than colourless and are priced accordingly.
When it comes to fancy coloured diamonds, a lot of things that are true for common colourless stones change. The main thing of course, is the colour — the more the better. Colour is graded by saturation: faint, fancy, intense and vivid. Vivid colours are the most beautiful, but also the most rare and expensive. Faint colours are much less impressive and are often priced at the same level as colourless stones or even below. The definitions of colour saturation are not as precise as the colourless grades, which causes some jewellers to mislabel diamonds with colour grades M or below as faint fancy yellow. They might want to actually charge much more for such diamonds, since they are fancy, but the truth is that no reputable grading lab would actually confirm such diamonds as fancy, so they should actually be priced much lower than higher colour grades such as D to J. Vivid and intense colours are the most valuable. You only have to see it once to understand why people are willing to pay high premiums for these stones.
Another aspect of colour is hue. As was noted above, diamonds are found in all colours of the rainbow and even more. Red and green diamonds are the rarest, while brown and yellow occur most often. Sometimes instead of calling a diamond brown a name like champagne or cognac is used. In addition to primary colours, diamonds can also exhibit a mixture of palettes: orange, purplish red, greenish yellow.
The last aspect that affect the appearance of a coloured diamond is its tone, the amount of grey discolouration of the hue. The lighter it is, the better the diamond will look, although some diamonds with noticeable gray tint still look impressive, particularly blue ones, which will be named steel blue if the amount of gray is significant.
Why are some diamonds coloured? Theoretically, a real pure diamond is absolutely colourless, but in practice, no diamond is ever perfectly pure (at least if it is of any reasonable size). The reason that some diamonds exhibit unusual colours is that their internal structure is somewhat different from a perfect carbon crystal.
There are several ways in which the crystal lattice can be modified to create a vivid coloured stone. One of them is to replace some of the carbon atoms with other elements. This can only be done during the original process of diamond creation, as atoms cannot be removed from a formed crystal. This is how yellow, brown and blue diamonds are created. Yellow and brown stones contain trace amounts of nitrogen, while blue ones contain boron. Blue diamonds, in addition to their beautiful colour, also have another interesting property — unlike any other diamonds, they conduct electricity. If you look at the periodic table, you will see that boron, carbon and nitrogen are all placed next to each other. This is no coincidence, as elements have to be similar in their properties to be able to replace each other in crystals. Faint yellow diamonds are relatively common, but they are not very attractive. Noticeable yellow tint can be seen even on diamonds that are graded K and lower on the colourless scale. Vivid and intense colours are very rare, and vivid yellows are only slightly more common than vivid blues.
Another way to colour a crystal is to actually modify its structure, while still keeping it all carbon. How and why these modifications occur is not very well understood, but they are what makes pink, red and purple diamonds. Until very recently diamonds in these colours were excessively rare, but diamond mines in Australia turned out to produce more of such diamonds than all other mines in the world together. Still, yearly production of all diamonds at the Australian Argyle mine would need a truck to be transported, but pink, red and purple diamonds mined in a year would barely fill an ashtray. While most rough diamonds are sold to dealers at set market prices, these coloured stones are almost always sold by the mine through annual auctions to the highest bidders.
Lastly, a diamond can be irradiated with certain radioactive materials, causing very unique changes to the entire crystal. Irradiation can occur naturally when diamond deposits are located near deposits of radioactive materials, or it can be induced in a laboratory. Irradiated diamonds are green, and are found very rarely in nature.
It is interesting to note that coloured diamonds are usually cut differently than colourless stones. This is because the cuts of colourless stones are optimized for maximum brilliance and brightness, while fancy coloured stones are cut to show off their colour and make it look as intense as possible. Fancy shapes (all that are not round brilliant) are often used because of their deeper pavilions. Since the colour of the diamond intensifies as it passes through more material, deeper pavilions tend to make colours more vivid.
The supply of fancy coloured diamonds is very limited and the prices are rather high, which means these unique stones are only slowly gaining popularity. Very few stores offer jewellery with natural coloured stones. Because of this every piece of fancy coloured diamond jewellery will be very unique and noticeable. These diamonds are perfect for people who desire something less traditional than a colourless diamond solitaire, for people who are not afraid to get attention. A fancy coloured diamond ring is one of the most unique and personal symbols of love that one can receive.
