Canadian diamond mining company Lucara Diamond Corp. unearthed what is believed to be the second-largest diamond ever found and will offer the 1,109-carat rough diamond in an auction on June 29.

Forbes reported that the stone, named “Lesedi la Rona” is the largest gem-quality rough diamond to be discovered in more than a century and the largest rough diamond in existence today and could fetch more than $70 million when it is auctioned by Sotheby’s in London.

The gem was unearthed by Lucara Diamond Corp., a Canadian diamond mining company, in November 2015, at its Karowe mine in Botswana. Around the size of a tennis ball (measuring approximately 66.4 x 55 x 4mm), this rough diamond of “exceptional transparency and quality” is around 2.5 to more than 3 billion years old, the auction house said.

Its name means “Our Light” in the Tswana language spoken in Botswana.

Sotheby’s said it has been more than 100 years since a diamond of this size and quality of the Lesedi La Rona has been found. Its size is exceeded only by the legendary Cullinan Diamond, mined in South Africa in 1905. The 3,016.75-carat diamond produced nine major diamonds that are part of the historic Crown Jewels of the United Kingdom, including the Great Star of Africa—considered to be the largest top-quality polished diamond in existence, weighing 530.20 carats.

According to Sotheby’s, The Gemological Institute of America said the Lesedi La Rona’s “top color and transparency exemplify the ‘limpid’ appearance commonly associated with type IIa diamonds,” which accounts for fewer than 2 percent of all gem-quality diamonds. They are considered “the most chemically pure and often show extraordinary optical transparency,” according to the GIA.

Sotheby’s adds that, according to independent reports, it has the potential to yield the largest top-quality diamond that has ever been cut and polished with an additional “high probability” that the resulting polished diamonds will be “D” color—the highest color classification for white diamonds.

“The Lesedi la Rona is simply outstanding and its discovery is the find of a lifetime,” said David Bennett, worldwide chairman of Sotheby’s Jewellery Division. “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.”

“We are very excited to be partnering with Sotheby’s on this landmark auction,” added William Lamb, president and CEO of Lucara Diamond Corp., “The forthcoming sale presents a unique opportunity to present this extraordinary diamond to a worldwide audience.”