Diamonds are the birthstone of April and one of the most sought-after gemstones all year round. They have captivated us for centuries due to their brilliance and are now ubiquitous as gifts for milestones in our lives.

In diamonds, we have learned to look for the absence of colour and inclusions, which are two of the 4Cs we always hear about – colour, clarity, cut and carat weight. However, they are not only colourless but diamond crystals with a variety of hues can also be mined in nature. Coloured variants are not as well known for several reasons, not least, their rarity and incredibly high price tag.

Diamonds: Colour

Before delving into specifics, it is crucial to remember that diamonds are composed of carbon atoms arranged in a tight crystal lattice structure. When carbon is joined in the structure by other impurities, they might affect the speed of the light travelling through the gemstones and therefore the final colours that appear to our eyes. For instance, nitrogen is the most common impurity causing yellow and brown hues. Conversely, boron impurities can produce a blue colour.

Moreover, as with many other fascinating features developed in nature, the colour can also come from a defect in their structure. When the crystal lattice undergoes deformation from the high pressure essential for diamond formation in the Earth’s mantle, it can create ‘colour centres’. The same might happen if they are exposed to particular kinds of radiation. These ‘colour centres’ absorb specific wavelengths of light, resulting in a coloured appearance.

Colour can also be produced artificially, replicating some of these processes that occur in nature. The market for coloured diamonds is niche, although the promotion of the Argyle mine in Australia is a good example of coloured diamonds attracting the wider public attention and being sold as collector pieces by jewellery shops and dealers alike. This mine, mostly known for pink diamonds, has brought to light a variety of other colours such as champagne, cognac, blue, violet, and the rare red. Production ceased in 2020, which has arguably made diamonds from Argyle and of good quality, even more attractive.

Specimens with good colour saturation tend to carry very high prices, especially if they have been certified as fancy-coloured diamonds. If your budget is on the smaller side, you might find it interesting and more convenient to have a look at diamonds with another secondary hue, such as ‘brownish-yellow’ instead of yellow, or ‘purplish-pink’ instead of pink, as when set in jewellery it might result difficult to notice any secondary colour. The same happens for the cut of the diamond, when purchasing a shape that is not the classic round brilliant, the competition will not be as fierce and consequently it will be more convenient.

Diamonds: The Trends

A new trend might also be identified in the so-called ‘salt & pepper’ diamonds as well as the ‘tinted’ ones. Both highlight the natural features of diamonds, the ‘salt & pepper’ are heavily included diamonds that would normally be discarded from being set in jewellery but are now having a ‘revival’ moment due to more and more people appreciating the natural inclusions and imperfect look. Diamonds described as ‘tinted’ are part of the ‘cape series’ of diamonds and lack the saturation to be considered ‘fancy diamonds’. They can, however, sometimes show attractive yellow hues and are used in jewellery as
a compromise with more expensive examples of fancy-coloured diamonds.

Diamonds at Auction

Assorted vari-shape 'purplish-pink' diamonds

Lot 31

Assorted vari-shape 'purplish-pink' diamonds, 9.24ct

Estimate: £150 - £200

Assorted brilliant-cut 'yellow' diamonds

Lot 33

Assorted brilliant-cut 'yellow' diamonds, 8.01ct

Estimate: £120 - £180

Marquise-shape diamond, 1.14ct.

Lot 69

Marquise-shape diamond, 1.14ct. With Anchorcert

Estimate: £700 - £900

Oval-shape 'brown' diamond

Lot 73

Oval-shape 'brown' diamond, 0.56ct

Estimate: £100 - £150

Colour-treated diamonds

Lot 74

Colour-treated diamonds, 1.22ct

Estimate: £50 - £80

Gemstones | Wednesday 1st May

Viewing times (ID required):

Birmingham

Friday 26th April 10:00 - 16:00

Tuesday 30th April April 10:00-16:00

Virtual viewings are available by request. Virtual viewings are the ultimate personal shopping experience. Using Zoom, you can ask us whatever you need to know in order to buy with confidence. Find out more here.