While diamonds are the epitome of all that is glamorous and dazzling in the gemstone sphere, nothing comes close to the mystique and allure of a deep red diamond. But as valuable and gorgeous as they are, red diamonds are also the rarest variety of coloured diamonds. Pure red diamonds are, in fact, so rare that only thirty of them have ever been mined.
Still, pink diamonds and red diamonds are not two separate types–pink diamonds are essentially red diamonds with a less saturated colour. During the colour grading process, a diamond with a weak to moderate colour saturation will be called a ‘pink diamond,’ while the term ‘red diamond’ is reserved only for those with a strong red colour and dark tone. Kimberley pink diamonds are naturally pink diamonds mined in Kimberley, Australia.
However, gemstone experts generally refer to pink and red diamonds as separate categories because of the differences in shade. Similar to how canary or intense yellow diamonds are rarer than their lighter yellow counterparts, pink diamonds are more commonly found than pure red ones.
Due to their delicate, blush colour, versatility, and lower price point, many people prefer pink diamonds to red. Although they have a lower value per carat, they are still very expensive and considered an exquisite diamond type, unless they are lab grown.
What Makes a Diamond Red in Colour?
Red diamonds are believed to have resulted from the impact of tectonic plate collisions that have taken place over millions of years. While most fancy colour diamonds owe their hues to higher nitrogen, hydrogen, or excessive pressure during formation, red diamonds–like clear diamonds–are made only of carbon.
The formation of red diamonds can be traced back to around 1.8 billion years ago when the Argyle mine in Australia was subjected to an ancient continental collision that compressed these rocks. This collision is thought to be responsible for dislocating carbon atoms in the Argyle diamonds, and the red colour is believed to have resulted from plastic deformation in diamond crystals.
This deformation refers to when carbon atoms along glide planes are slightly displaced, and this atomic structural difference in red diamonds causes light to bend through the irregular lattice of the stone, giving them a pink or red hue. Only in very rare circumstances are enough glide planes present to produce a more intense saturation of colour, causing a stunning, deep red diamond to form.
This means that the colour of red diamonds is essentially a trick of light dispersion, and they can look different in various lighting. For instance, the red hue stands out the most in candlelight or natural daylight. While they will never look colourless, the red isn’t always as rich when viewed in fluorescent lights.
How Are Red Diamonds Graded?
The grading of red diamonds is done on a different scale than other fancy colour diamonds. Coloured diamonds, in general, are not graded on the usual D to Z scale, as the depth of colour and intensity has to be accounted for differently than with clear diamonds.
Fancy red diamonds are considered highly saturated pink diamonds and are therefore graded on the basis of their tone, clarity, and warmth, as well as how light or dark red they are. Grading these diamonds is tough, and the Gemological Institute of America does not have an accurate standardised scale listed for these stones. Part of the reason is their rarity, which makes it harder to come across enough of these gems to establish comparative grading.
Generally, however, tone colours play an important part in determining the value of fancy red diamonds. Those with purplish or pure red tones are worth much more than orangey or brownish-red diamonds. Lighter red or pink diamonds are also generally valued more than those with orange or burgundy tints–you can check out a pink diamond colour chart here.
Searching for that perfect pink or red diamond and curious about how to check diamond quality? We’ve got you covered–take a look at our recent post!