Petra unearths 232-carat white diamond in South Africa

Shares in mining company expected to climb on second major discovery this year

Petra Diamonds has discovered a D colour Type II diamond that it claims is of "exceptional size and clarity"

Petra Diamonds said on Tuesday it had recovered an "exceptional" 232 carat white diamond at its Cullinan mine in South Africa, the source of many of the world’s largest gems.

The diamond miner, which has five producing mines in South Africa and one in Tanzania, said it expected the diamond (which has no measurable nitrogen impurities), to be sold in the second quarter of its current fiscal year ending June 30, 2015.

Prices for polished diamonds over the past year

The price of polished diamonds over the past year

In June, Petra unearthed a blue diamond weighing in at 122.5 carats. Analysts from broker Sanlam roughly estimated that it would be worth $35m and the discovery resulted in the shares climbing by more than 6pc in the subsequent week.

The company recently embarked on a big investment programme to extend the economic life of some of its older mines – many of which have been in operation for over a century.

At its full-year trading update in July, Petra said that its gemstone production was ahead of expectations – up 17pc on the previous year to 3.1m carats in the 12 months to the end of June.

The Cullinan mine was the source of the world’s biggest ever diamond, the 3,106-carat Cullinan diamond, which was discovered in 1905. It was cut into two stones. One of these is the First Star of Africa, which is mounted at the top of the Sovereign's Sceptre and, at 530 carats, is the largest flawless cut diamond in the world. It forms part of Britain’s Crown Jewels which are held in the Tower of London.

Share price of Petra Diamonds over the past year

Share price of Petra Diamonds over the past year