Although under its original estimate the rare blue diamond, discovered by Petra Diamonds has sold for $28 million this week. The gem was discovered earlier this year in June at the famous Cullinan mine in South Africa and was predicted to hit an all time world record in the blue diamond market. Although the gem sold for a significant sum, the total was fell under the $35m to $50m experts were expecting. The chief executive from Petra said the sale was an “excellent sales value for the rough stone”. Petra Diamonds also retained a 15% stake in the stone which will be cut and polished by the buyer before going on sale again – increasing the profits for the diamond mining giants. The Cullinan mine has unearthed some of the most rarest diamonds in the world including the largest rough diamond ever found at 3106 carats which was then cut in two and set in the Queens crown jewels and named the First and Second Star of Africa. So there’s great hope for this blue stone yet.