Petra Diamonds sees "exceptional" blue diamond boosting second half

(Reuters) - Petra Diamonds posted a 19 percent rise in first-half revenue, lifted by output from the miner's key Finsch mine in South Africa. The London-listed miner said the "exceptional" 29.6 carat blue diamond it unearthed at the Cullinan mine would lead to strong second-half revenue. Petra, which has seven producing mines in South Africa and one in Tanzania, reiterated its 2014 production guidance of about 3 million carats for the year ended June 30, 2014. Revenue increased to $185.5 million in the six months ended December 31, from $156.3 million a year earlier. Petra said it produced 1,635,716 carats during the period, up 31 percent from the year earlier.