London—Gemfields announced that its latest auction of rough Zambian emeralds, held in London, generated $7.5 million in sales, the highest auction revenues that the company has achieved to date.

Demand for Gemfields' Kagem emeralds has steadily increased across all sectors over the past year, according to a news release issued this week from the company, which touts its Zambian-mined emeralds as meeting high levels of environmental and ethical standards all along the route to market.

"The markets for diamonds and gemstones continue to show clear signs of recovery, with per- carat prices received by Gemfields rising dramatically," Gemfields Chief Executive Officer Ian Harebottle said in the release.

The auction of predominantly higher quality rough emeralds was held in London from July 19 through July 23, and was attended by 37 "premium," hand-selected companies hailing from India, Israel, Germany and the United States, the company said.

All told, the July auction saw a total of 850,000 total carats offered, with 800,000 carats ultimately bringing in the $7.5 million in sales. The per-carat prices achieved at the auction were 83 percent higher than they were at Gemfield's previous auction, held in November 2009, which featured similar higher-quality material.

Together, the company's four auctions held since July 2009 (two in London, one in Jaipur, India, and another in Johannesburg, South Africa) have generated revenues totaling $26.2 million.

For the quarter ending 30 June 2010 saw solid production volumes, good grades and the lowest quarterly unit production costs achieved to date, the company said. The year ending 30 June 2010 saw Kagem's operating costs fall 42 percent, with gemstone production down 38 percent, "indicative that the new mine plan is achieving true economies of scale,' the release said.