Sotheby's Diamonds showcase world's rarest white rock

Its value is believed to be around £25 million though Sotheby's who unveiled the 102.34 carat rock as part of their first year anniversary celebrations have put it on the market for an undisclosed sum.

Extraordinarily rare, the white diamond, mined in Botswana, is the only known round brilliant-cut diamond over 100 carats with an extra cachet of being flawless in colour and clarity. It is the largest, round D colour flawless diamond ever to come to light.

Sotheby’s Diamonds Founder and Chairman Patti Wong, said:

“This stone is over 100 carats of flawless perfection. In the course of my long career, which has brought me close to some of the greatest stones the earth has ever yielded,

"I have not encountered anything quite like this. With its outstanding weight, its perfect colour, clarity and cut, it is a masterpiece of nature brought to life by human hand, blazing with a brilliant firework-like display of almost every colour on the spectrum - mesmerising to behold.

"It is a huge privilege to mark the first anniversary of our London Salon with the exhibition of such a superlative stone.”

According to Sotheby Diamonds, the  D Flawless Round Brilliant stone, like the famous Cullinan I and Koh-i-noor diamonds, which are part of the British Crown Jewels, is part of the rare subgroup comprising less than 2% of all gem diamonds, known as Type IIa.

Diamonds in this group are the most chemically pure type of diamond and often have exceptional optical transparency.