Petra Diamonds has recovered a 232.08 carat white diamond at its Cullinan mine in South Africa, which three analysts said could fetch between $10 million and $16 million.

Shares in the diamond miner climbed as much as 6.5 percent in early Tuesday trading, the biggest rise on Britain's FTSE-250 Midcap Index.

The find is Petra's largest of a white diamond since it unearthed the 507-carat Cullinan Heritage diamond in 2009 from the same mine, the source of many large diamonds.

That rough diamond - whose clarity grade was assigned as "flawless" - fetched a record price of $35.3 million.

"We estimate a sales price in the order of $10 million to $15 million, given Gem Diamonds' recent sale of Type II white at about $70,000 per carat and assuming some losses for cutting/polishing," Numis Securities analysts said in a note.

The diamond miner, with five producing mines in South Africa and one in Tanzania, said it expected the diamond that has no measurable nitrogen impurities to be sold in October-December, the second quarter of its financial year.

The Cullinan mine boasts the largest rough gem diamond ever recovered - the 1905 Cullinan Diamond, which was cut into two stones that are part of Britain's Crown Jewels.

Petra bought the mine from Anglo American Plc's De Beers unit, the world's biggest diamond producer by value.

The miner's stock was up 6.1 percent to 187.6 pence at 0730 GMT on the London Stock Exchange. - Reuters