The world’s most expensive Diamond: The Pink Diamond

We explore one of the world's most expensive gemstones: the pink diamond.

When it comes to diamonds there are many factors to take into consideration when calculating their value. When you’re looking for the ideal stone to feature in a ring, necklace or bracelet it’s important to be aware of why some diamonds are more expensive than others and what factors are at play to determine that.

The main way in which diamonds are categorised is through assessing the four C’s. By looking at these four areas and assigning a value, different diamonds can be given an exact price that is a fair reflection of their quality. The four C’s are cut, clarity, colour and carat. 

Whilst all four of these categories are important to determining the diamond’s final selling price, there are some elements that play a greater role than others. The carat, for example, indicates the weight of the stone so it would make sense for a heavier diamond to cost more. However, it is the colour that can really cause a diamond’s value to skyrocket.

What is a Pink Diamond?

A pink diamond is an incredibly rare coloured stone that includes a pink hue. Its unique colouring makes these diamonds highly sought after and, thanks to their rarity, one of the most expensive diamonds in the world.

Over 90% of the world’s pink diamonds are mined in Australia, specifically the Argyle mine in the northwest of the country. Although most are found here, there have been instances of pink diamonds being found in India, Canada, South Africa, Russia and Brazil. Interestingly, the Argyle mine where most of the diamonds were mined was closed in 2020, meaning pink diamonds are set to become even rarer.

Less than 1% of the diamonds mined at the Argyle were pink, meaning for every million carats of rough diamond mined, only one carat of pink diamond was found suitable for selling. Only around 40 - 50 carats of pink diamonds are sold at auction around the world annually.

What Makes a Diamond Pink?

Regular diamonds, such as those commonly found on engagement rings, are created thanks to vertical kimberlite pipes, a natural phenomenon where kimberlite can be found. This kimberlite is what often houses diamonds. 

However, when it comes to pink diamonds, particularly the ones mined in Australia, the usual kimberlite pipes are replaced by volcanic lamproite ones. Scientists believe this is a key reason for so many coloured diamonds being found here. 

Despite the different geological conditions, the exact reason for their pink appearance is still subject to speculation. The hypothesis that most researchers agree on is that the colour is caused thanks to a process known as ‘plastic deformation’. This is where the gemstone has been forced to the surface and the structure has somehow changed en route, causing deformation and allowing the stone to absorb light differently. This change is what causes them to emit their signature pink hue.

How Rare are Pink Diamonds?

Pink diamonds are exceptionally rare. So much so that only roughly 1 in 10 million mined diamonds are coloured enough to be classed as fancy. Some experts even predict that there are only 500 left that are undiscovered in the entire world.

In recent years demand has increased while supply has remained very limited. This means that pink diamonds only come up for sale a handful of times each year with high-quality stones regularly fetching tens of millions of pounds. What is a pink diamond worth? Well, ‘The Sakura’, a flawless pink/purple diamond owned in Hong Kong recently fetched just shy of £22 million at auction.