A 25.5-carat blue diamond found at Petra Diamonds' Cullinan mine. Picture: PETRA DIAMONDS
A 25.5-carat blue diamond found at Petra Diamonds' Cullinan mine. Picture: PETRA DIAMONDS

London — Petra Diamonds has sold a 20-carat blue gem for almost $15m, a major boost for the company that’s struggling with a mountain of debt and falling diamond prices.

The company found the diamond in September at its Cullinan mine in SA, famous for producing expensive gems including those in the British crown jewels. Blue gem-quality stones are among the most valuable in the world, and the diamond sold for $741,000 per carat.

Petra shares jumped as much as 11%, the most in more than a month, to 9.45p. The buyer wants to remain anonymous, Petra said in a statement on Friday.

The company has had a rough few years. Its share price collapsed to a record low last month amid falling diamond prices and concerns that it will struggle to repay debts.

In September, it wrote down the value of its mines by almost $250m and said co-founder and chair Adonis Pouroulis will leave. This follows the departure of Petra’s long-serving CEO in the year.

Petra has slid from a peak value of more than $1.5bn as it redeveloped the Cullinan mine, where the world’s biggest diamond was found in 1905. The cost of that project saw Petra’s debts swell, just as the diamond market weakened.

Bloomberg