A colossal diamond from Botswana the size of a tennis ball and three billion years old is expected to fetch in excess of $70 million at a Sotheby’s auction in the UK next month.

The 1109-carat Lesedi la Rona is said to be the largest gem-quality rough diamond to be discovered in over a century and the largest rough diamond in existence.

It will be sold in a stand-alone Sotheby’s sale in London on June 29 and is estimated to achieve in excess of $70 million.

The Lesedi la Rona – which means “Our Light” in the Tswana language spoken in Botswana – was uncovered by Lucara Diamond Corporation in November 2015, at their Karowe mine in Botswana. 

Around the size of a tennis ball (measuring approximately 66.4 by 55 by 42 mm), this colossal rough diamond of exceptional transparency and quality is around 2.5 to over 3 billion years old.

Diamonds have been mined continuously for centuries in multiple locations around the world and yet nothing of the size and quality of Lesedi La Rona has been found in over 100 years. 

In terms of its size, the rough is exceeded only by the legendary Cullinan Diamond, mined in South Africa in 1905. 

The 3016.75-carat Cullinan Diamond produced nine major diamonds that are part of the historic Crown Jewels of the United Kingdom, including the Great Star of Africa – currently the largest top- quality polished diamond in existence, weighing 530.20 carats.

According to a study by the Gemological Institute of America (GIA), the Lesedi La Rona’s “top colour and transparency exemplify the “limpid” appearance commonly associated with type IIa diamonds” – a rare and coveted subgroup which comprises less than 2 per cent of all gem diamonds. Stones in this group are “the most chemically pure and often show extraordinary optical transparency".

David Bennett, Worldwide Chairman of Sotheby’s Jewellery Division, commented: “The Lesedi la Rona is simply outstanding and its discovery is the find of a lifetime. It is a huge honour for Sotheby’s to have been entrusted with its sale. Every aspect of this auction is unprecedented. Not only is the rough superlative in size and quality, but no rough even remotely of this scale has ever been offered before at public auction.”

William Lamb, President and Chief Executive Officer of Lucara Diamond Corporation, said: “We are very excited to be partnering with Sotheby’s on this landmark auction. Lucara has made innovation the cornerstone of its development strategy and this has led to the historic recovery of the Lesedi La Rona diamond. The sale presents a unique opportunity to present this extraordinary diamond to a worldwide audience.”

The Lesedi la Rona will be on view at Sotheby’s New York on May 7, and at Sotheby’s London from June 18 to 28, ahead of its auction in the evening of June 29.