500-carat diamond found at S. African mine
Chicken-egg-sized stone may be among world’s top 20 high-quality gems
 Petra Diamonds/ho / EPA Petra Diamonds Chief Executive Johan Dippenaar holds a white diamond weighing 507.55 carats, which was excavated at the historic Cullinan mine in South Africa on Sept. 24, 2009. |
JOHANNESBURG – Petra Diamonds Ltd. says a diamond the size of a chicken egg has been found at South Africa’s Cullinan mine.
The diamond may be among the world’s top 20 high-quality gems. It was discovered Thursday at the mine northeast of Pretoria, South Africa.
Johan Dippenaar, the company’s chief 
