Colour stones, also known as fancy coloured diamonds, are natural diamonds that exhibit colour in hues other than classic white or yellow. Unlike white diamonds which gain their colour from chemical impurities of nitrogen, colour stones exhibit their rainbow of hues from trace elements present during their formation, such as boron and nitrogen. The most prized and rare colour stones are vivid red, blue, pink, purple and green.
What Causes the Different Colours in Diamonds?
The various colours in natural colour diamonds are caused by the presence of certain chemical elements and structural anomalies during the diamond’s formation deep within the Earth’s crust. Here are the main factors that produce colour in diamonds:
| Element/Factor | Colour Produced |
|---|---|
| Nitrogen | Yellow, brown, orange, pink |
| Boron | Blue |
| Hydrogen | Purple, pink, red, orange, blue |
| Lattice Dislocations | Pink, red, purple |
| Radiation Exposure | Green, blue, pink |
The most common colour causing element in diamonds is nitrogen. When nitrogen atoms replace carbon atoms in the diamond’s crystal lattice structure during formation, they absorb light in the blue end of the spectrum producing yellow and brown hues.
Boron impurities result in blue diamonds, as boron absorbs red and green light. Hydrogen impurities are linked to rare red, pink, orange and purple diamonds.
Lattice dislocations during formation can also cause pink, purple and red colours. Exposure to radiation can knock electrons out of their usual positions in the crystal lattice, causing green, blue and pink colours. The rarer the colour, the higher the value of the diamond.
Natural Colour vs. Treated Colour Diamonds
There are two main categories of colour diamonds:
1. Natural Colour Diamonds – These diamonds display natural colour elements present during their formation in the Earth’s mantle. They are extremely rare and account for less than 0.1% of mined diamonds.
2. Treated Colour Diamonds – These originally brown or yellow diamonds have been artificially treated to change or enhance their colour, usually by exposure to radiation or high heat. This treatment is permanent but does lower value compared to untreated colour stones.
It is important to have a colour diamond certified by a reputable lab like GIA or AGS to authenticate its natural colour origin. Reports will state “natural colour” or specify the type of treatment used otherwise. Consumers should steer clear of diamond dealers who do not provide official grading reports.
Grading Colour Diamonds
The grading of colour diamonds differs from colourless diamonds that are graded on a D-to-Z scale by GIA and AGS labs. Those scales only measure absence of colour. Grading natural colour diamonds requires judging hue, saturation, tone and uniformity of the colour present.
GIA uses a descriptive grading system with fancy colour descriptors along with intensity levels from Faint to Vivid. For example: Fancy Light Pink, Fancy Intense Yellow. AGS (American Gem Society) uses a similar numeric scale from 1-10 for hue and saturation. Both labs will comment on uniformity of colour distribution.
Most Prized Diamond Colours
In general, vividly saturated colours are the most prized, rare, and expensive. Some of the top diamond colours and their distinguishing traits are:
| Colour | Distinguishing Factors |
|---|---|
| Red | – The rarest diamond colour, commanding record prices |
| Pink | – Vivid pinks are very rare. Caused by lattice deformities. |
| Blue | – Intense blues due to boron impurities are prized but very rare. |
| Green | – Vivid greens result from natural radiation exposure. |
| Purple | – A combination of blue and pink producing a vivid purple. |
| Orange | – Pure oranges with no brown are the most valued. |
| Yellow | – Pure yellow not mixed with brown or grey hues. |
While vivid colours fetch high prices, even pale shades from champagne to olive can see significant value compared to equivalent colourless diamonds.
Where Do Natural Colour Diamonds Come From?
While colour diamonds constitute less than 0.1% of global diamond production, certain mines around the world are famous for yielding coloured diamonds:
– **Argyle Diamond Mine** – This mine in Australia produces 90% of the world’s prized pink, red and champagne diamonds. It closed in 2020 after being depleted.
– **Golconda Region** – Historic mine in India renowned as the source of the famous colourless Kohinoor and blue Hope diamonds.
– **Cullinan Mine** – South African mine renowned as the original source of many famous large colourless and coloured diamonds.
– **Kollur Mine** – Historic mine in India’s Guntur district that was the original source of many famous yellow diamonds.
– **Crater of Diamonds** – A State Park in Arkansas USA where many coloured diamonds have been found by the public.
Famous and Historical Colour Diamonds
Some of the most famous natural colour diamonds known for their unique colours, histories and record prices include:
| Diamond Name | Details |
|---|---|
| Hope Diamond | – 45.52 carats, deep blue, originally from India’s Kollur mine |
| Hancock Red | – 0.95 carats, the finest reddish purplish red, discovered in West Africa |
| Moussaieff Red | – 5.11 carats, vivid red, the record price per carat for any gemstone |
| Blue Moon | – 12.03 carats, vivid blue, sold for $48 million in 2015 |
| Pink Star | – 59.60 carats, vivid pink, sold for record $71 million in 2017 |
| Wittelsbach-Graff | – 31.06 carats, deep blue, originally mined in India in the 17th century |
| Steinmetz Pink | – 59.60 carats, vivid pink, largest known fancy vivid pink diamond |
| Allnatt | – 101.29 carats, yellow, discovered in South Africa in the early 20th century |
These diamonds and others like them are testament to the mystery, intrigue, beauty and rarity inherent in the world’s most prized natural colour diamonds. Their stories contribute a romantic mystique that feeds demand among collectors.
Are Colour Diamonds a Good Investment?
Investing in rare colour diamonds can be an excellent way to achieve portfolio diversification into hard assets, similar to investing in gold or other precious metals and gemstones. However, proper authentication and buying at wholesale prices is key.
Pros of investing in natural colour diamonds include:
– Scarcity – Less than 0.1% of diamonds exhibit natural colour, creating rarity.
– Value Growth – Rare vivid pink and blue diamonds have seen values rise 500% over the past decade.
– Romantic Allure – Colour diamonds possess intrigue and beauty that feeds demand.
– Diversification – Uncorrelated to stocks and bonds making them a portfolio diversifier.
Cons to keep in mind:
– Illiquidity – coloured diamonds can take time to sell depending on colour and demand cycles.
– Authentication – Ensuring natural origin versus treated colour is critical.
– Valuation Complexity – precise colour grading and market values can be challenging to assess.
Overall, investing in rare, authenticated natural colour diamonds of 2 carats or larger can provide nice diversification and upside potential for those who properly research and source stones wholesale. Smaller dealers historically provided the best access for investors versus retail.
How to Buy and Evaluate Colour Diamonds
Those looking to buy natural colour diamonds as an investment or fashion accessory should follow these tips:
– Review GIA or AGS certificate to ensure “natural colour” and no evidence of treatment.
– Compare wholesale price versus retail markup to identify good values.
– Focus only on colours that are more rare like vivid pinks, blues and reds which see demand growth.
– Fancy intense/vivid grades will appreciate faster than faint/light grades.
– Larger diamonds over 2 carats in rare colours will have more investor appeal.
– Buy from established dealers with access to ethical, wholesale supply chains.
– Take time to learn market values for different colour grades before purchasing.
By taking the time to properly research and source natural colour diamonds at wholesale prices, they can be a rewarding long-term investment.
Conclusion
In summary, natural colour diamonds exhibit an array of hues from trace elements present when they formed deep within the Earth. Vivid pinks, reds, greens and blues are exceptionally rare and coveted. Proper authentication and buying at wholesale prices is key to realizing upside as an investor. Coloured diamonds possess intrigue, beauty and scarcity that feeds growing demand and makes them a diversifying asset for portfolios needing hard asset exposure. But proper due diligence is required to identify natural colour origin and attractive valuations in the market.
