(IDEX Online) - Petra Diamonds has announced another high-value sale from the iconic Cullinan mine - a 299.3-carat white, Type IIa gem for $12.18m.It follows the sale last November of the Letlapa Tala collection of blue rough diamonds, also recovered from Cullinan and weighing a total of 85.6 carats to De Beers and Diacore for just over $40m.The "exceptional" new find (pictured) was sold to Stargems DMCC, Dubai-based arm of the Antwerp diamond supplier.The price of $40,701 per carat, was higher than the $34,386 per carat achieved in May 2019 by the 424.89-carat Legacy of the Cullinan Diamond Mine.Richard Duffy, CEO of the UK-listed miner, said: "This is another significant sale for Petra Diamonds, following the sale of the Letlapa Tala Collection in November 2020, and a further endorsement of the quality of the Cullinan ore body which is known for its exceptional stones."Petra reported an eight per cent drop in its revenue to $178.1m in the six months to 31 December 2020, as COVID-19 depressed prices and allowed fewer tenders to take place. A deal to restructure some of its $650m of debt should be complete by March.