The largest rough diamond ever sold at auction has been purchased for US$53 million, or about C$65.6 million.

The tennis ball-sized stone was uncovered at a mine in Botswana in 2015, run by Vancouver-based Lucara Diamond Corporation.

The 1,109-carat Lesedi La Rona diamond was purchased by British jeweller Graff Diamonds, Lucara said in a statement Monday. The stone's name translates to "Our Light" in Tswana, the national language of Botswana.

In a statement on its website, Graff Diamonds called the stone the most valuable rough diamond in the world, and referred to it as a "gift from Mother Nature."

New owner Laurence Graff said his company was "thrilled and honoured to become the new custodians of this incredible diamond."

Graff called it a momentous day in his career, and said the company will cut now decide how to cut and polish the stone.

"The stone will tell us its story. It will dictate how it wants to be cut, and we will take the utmost care to respect its exceptional properties," he said in the statement.

Josh Raber, president of wholesaler Vancouver Diamonds, told CTV News he expects Graff to make as few changes as possible to the rough stone.

"What they want to do is maximize the most amount of money they can get out of that rough. They want to keep it as big as possible, but who knows how big of a diamond they can actually cut at the end of the day," Raber said.

Graff Diamonds also owns a 373-carat diamond, purchased earlier this year, which was part of the same stone the Lesedi came from.

While Lucara said Graff's winning bid was an improvement on an offer received last year, Sotheby's had estimated the stone would sell for US$70 million (C$86 million).

The largest gem-quality rough diamond ever found was 3,106.75 carats, found in what is now South Africa in 1905. The Cullinan Diamond was given to King Edward VII and cut into several polished gems.

The Lesedi is the largest gem-quality rough diamond discovered since the Cullinan.