Just months ago, a 29.6ct blue diamond from Petra Diamonds' Premier Mine sold for more than £15 million at auction. If this latest find is valued similarly - £508,000 per carat - it could fetch more than £60 million.

Just months ago, a 29.6ct blue diamond from Petra Diamonds' Premier Mine sold for more than £15 million at auction. If this latest find is valued similarly - £508,000 per carat - it could fetch more than £60 million.

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