A mining firm says an 'exceptional' 122-carat blue diamond has been discovered.
It was found at the Cullinan mine in South Africa.
Shares in London-based Petra Diamonds - which runs the mine - have risen more than 6 per cent on the news.
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The company said in a statement: "The rarity of a blue diamond of this magnitude sets it apart as a truly significant find.
"The stone will require further analysis in order to assess its potential value and upon completion of this process, Petra will be in a position to evaluate its optimal route to market.
"The diamond will, therefore, not be sold before the end of the company's current financial year (June 30)."
