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The biggest diamond to be found in over a century will go on sale, but is difficult to value as there is no precedent for it, say its owners.

William Lamb, CEO of the Lucara Diamond Corporation - owners of the Karowe Diamond - said, "It's just smaller than a tennis ball [...] a stone of this size has never actually been sold before".

It is the biggest diamond to be discovered in Botswana and the largest find in more than a century.

The 1,111-carat stone, was recovered from the Karowe mine, about 500km (300 miles) north of the capital, Gaborone.

Although it is yet to be valued, Lamb said a 507 carat stone recovered in 2009 in Petra "sold for 35 million dollars".

This clip is originally from 5 live Breakfast on November 20th 2015.