Petra sells two rare diamonds for $13.5 million

South Africa’s Petra Diamonds (LON: PDL) has sold its recently recovered 342.92-carat Type IIa white diamond and an 18.30-carat Type IIb blue diamonds for a combined $13.5 million.  The company said it will receive upfront payments of $10 million for the white stone and $3.5 million for...