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The world's second-largest gem-quality diamond has been sold to a London jeweller for $53m (£39.5m).

Laurence Graff, chairman of , bought the diamond privately after it failed to meet its reserve price at an auction last year.

The 1,111-carat stone was recovered by Canadian firm Lucara Diamond Corp in Botswana two years ago.

Lucara said the price was an improvement on the highest bid received at in June 2016.

The diamond is named "Lesedi La Rona", which means "our light" in Botswana's Tswana language.

The stone was first formed between 2.5 and three billion years ago and is roughly the size of a tennis ball.

As well as its size, the diamond has been certified as being of "exceptional quality and transparency" by the Gemological Institute of America.

Mr Graff said "The stone will tell us its story, it will dictate how it wants to be cut."

The company says it will be scanned using state-of-the-art 3D equipment that searches for inclusions - small imperfections in the heart of the stone - to decide how the diamond will be polished.

Then an expert team will examine the diamond using microscopes to pick up and navigate any further pinpoint inclusions.

They will then work out how to cut the diamond and into how many individual stones.

Graff acquired another 373-carat diamond that was originally part of "Lesedi La Rona" earlier this year.

The company says it will cut the smaller diamond first and with the knowledge gained from that, they will decide how to work on the larger gem.

The "Lesedi La Rona" is the largest gem-quality diamond discovered in more than a century, and the second-largest ever. The largest was the 3,106-carat Cullinan Diamond, discovered in South Africa in 1905.

Graff described the stone as "the world's most valuable rough diamond".