Vancouver-based Lucara Diamond Corp. has sold what it says is the second largest gem-quality diamond ever found.

The company announced Monday that the Lesedi La Rona, an 1,109 carat-sized stone unearthed in 2015, has sold for $53 million US.

The new owner, Laurence Graff of British multi-national jeweler Graff Diamonds, said becoming the "custodian" of the diamond was the highlight of his career.

"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.

The diamond measures 65 by 56 by 40 millimetres. It was unearthed in 2015 in Lucara's Karowe mine in Botswana.

massive diamond sold

Vancouver based Lucara hits the motherlode with sale of world's second largest rough cut diamond.

The stone was the biggest gem-quality diamond discovered since the famed Cullinan, measuring more than 3,000 carats, was found in South Africa in 1905. The Cullinan was subsequently cut into smaller pieces, with the two largest portions incorporated into Britain's Crown Jewels.

'Discovery of a lifetime'

David Bennet, the chairman of Sotheby's jewelry division in Switzerland, called the find the "discovery of a lifetime" shortly after it was unearthed.

"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," said Bennet.

The massive stone was up for auction at Sotheby's in June 2016 — but bidding stalled and the stone remained in Lucara's possession — until Monday.

The Lesedi La Rona wasn't  the only one for the record books unearthed that day in 2015. A diamond measuring 813 carats — and another measuring 374 carats were pulled from the mine.

The 813 carat Constellation diamond sold for the record setting price of $63 million in 2016. It stands as the most expensive rough diamond ever sold.