Why are there coloured diamonds, and why are they so expensive?

Diamonds have long been cherished for their brilliance and rarity, but when it comes to coloured diamonds, their allure reaches a whole new level. These stunning gems can come in a spectrum of hues, from soft pinks to deep blues, vivid greens, and even fiery yellows. But what causes diamonds to exhibit such vibrant colours? And why do coloured diamonds often command prices far higher than white diamonds?

In this blog post, we’ll dive into the fascinating world of coloured diamonds, exploring how they form, the factors that contribute to their value, and why they have become some of the most expensive and sought-after gems in the world.

How Do Diamonds Get Their Colour?

Diamonds are made almost entirely of carbon atoms. In their purest form, diamonds are colourless, as light passes through the crystal structure without being absorbed. However, nature rarely produces diamonds in their "perfect" form. When other elements or structural irregularities are introduced during the diamond’s formation, they can alter how the diamond interacts with light, resulting in the beautiful colours we see.

Here are some of the main causes of colour in diamonds:

1. Trace Elements

The presence of certain elements can cause diamonds to develop various colours:

• Nitrogen: When nitrogen atoms are present in the diamond’s structure, they absorb blue light, giving the diamond a yellow or orange hue. 
• Boron: Boron impurities cause diamonds to appear blue by absorbing yellow light. Famous blue diamonds like the Hope Diamond owe their color to boron.
• Hydrogen: In some cases, hydrogen can cause diamonds to exhibit rare colors such as purple or violet.

2. Structural Distortions

During a diamond’s formation, high pressure and temperature can cause irregularities in its crystal lattice. These distortions can result in certain colours:

• Pink and Red Diamonds: Scientists are still studying the precise reasons behind these rarest of colours, but many believe that plastic deformation—structural changes during a diamond’s formation—causes the unique light absorption patterns seen in pink and red diamonds.

3. Natural Radiation

Green diamonds form when diamonds come into contact with radioactive minerals over millions of years. The radiation changes the crystal structure, resulting in a green hue. These diamonds are extremely rare and can range from faint green tints to intense shades.

Why Are Coloured Diamonds So Expensive?

Coloured diamonds are not just visually striking—they are also some of the rarest diamonds in the world, and this rarity plays a significant role in their high prices. But there’s more to their expense than just rarity. Here are the main factors that make coloured diamonds so valuable:

1. Rarity

Colored diamonds are incredibly rare compared to their colourless counterparts. For every 10,000 colorless diamonds mined, only one coloured diamond is found. Some colours, like red, green, and blue, are so rare that they make up less than 0.1% of all diamonds discovered. The rarity of these diamonds makes them highly coveted by collectors and investors alike.

For example:

• Red Diamonds: Among the rarest, red diamonds are so uncommon that only a handful of pure red diamonds have ever been discovered. This extreme scarcity makes them some of the most expensive diamonds in the world.
• Pink Diamonds: The Argyle Mine in Australia, known for producing most of the world’s pink diamonds, has contributed to the rising demand and price of these stones. The closure of the Argyle Mine in 2020 has made pink diamonds even more valuable due to limited future supply.
• Blue Diamonds: Diamonds like the Hope Diamond, which are blue, are incredibly rare due to the limited presence of boron in the Earth’s mantle. This rarity, combined with the mystique surrounding famous blue diamonds, drives up their prices.

2. Intensity of Color

In coloured diamonds, the strength and purity of the colour dramatically affect the price. Diamonds are graded on a scale that ranges from “faint” to “vivid,” with vivid diamonds exhibiting the most intense and valuable colours. A faintly coloured diamond will generally be less expensive than one with a vibrant, deep hue.

For example, a fancy vivid pink diamond will command a much higher price than a faint pink diamond of the same size and quality. The rarest diamonds with intense colors, especially in shades like red, blue, or green, can fetch prices in the millions per carat.

3. Market Demand and Trends

The luxury market plays a significant role in the pricing of coloured diamonds. Over the years, certain coloured diamonds have gained popularity due to celebrity endorsements, high-profile auctions, and limited supply. For instance, famous pink and blue diamonds like the Pink Star and the Blue Moon Diamond have sold for record-breaking prices at auction, drawing attention to these gems and increasing demand.

• Celebrity Influence: When celebrities wear colored diamonds, it sparks public interest and drives up demand. For example, Jennifer Lopez’s pink diamond engagement ring from Ben Affleck made pink diamonds incredibly popular.
• Investment Value: Many investors see rare coloured diamonds as a secure and appreciating asset. Since the supply of naturally coloured diamonds is limited, their value is expected to increase over time.

4. Cut and Size

Cut and size also contribute significantly to the price of coloured diamonds. Because the colour of the diamond is its most valuable characteristic, gem cutters often focus on maximizing the gem’s colour intensity rather than its brilliance. A well-cut coloured diamond that enhances the stone’s hue will fetch a much higher price. Additionally, large coloured diamonds are extremely rare, and the larger the stone, the more valuable it becomes.

Are Lab-Grown Coloured Diamonds More Affordable?

While natural coloured diamonds are rare and expensive, there are alternatives for those who want the beauty of a coloured diamond without the hefty price tag.

• Lab-Grown Coloured Diamonds: Advances in diamond-growing technology have made it possible to create coloured diamonds in laboratories. These diamonds are chemically and physically identical to natural coloured diamonds but are generally more affordable since they are created under controlled conditions rather than formed over millions of years.

Conclusion

Coloured diamonds are nature’s rare and vibrant masterpieces, each one possessing a unique story written in its hue. Their stunning colours, caused by trace elements, structural distortions, or radiation, make them highly sought after. But it’s their rarity, the intensity of their colour, and the demand for these jewels that drive their extraordinary prices.

Whether it's a delicate pink, a mysterious blue, or a vivid yellow, coloured diamonds have captured the fascination of collectors, jewelers, and investors alike, making them one of the most precious and valuable gems in the world. And while they may be expensive, their rarity and beauty ensure that they will remain timeless treasures for generations to come.