Zimbabwe became the world’s seventh- biggest diamond producer by value in 2010, up from 13th the previous year, statistics released by the Kimberley Process and New York-based Rapaport show.

The southern African nation produced gems worth $339.8 million last year, up from $20.4 million in 2009, the reports show. The value of a carat from Zimbabwe almost doubled from $21.20 to $40.28 in the same period.

The jump came after the Kimberley Process, which monitors the export of so-called conflict gems, allowed limited sales of diamonds from Zimbabwe’s contested Marange diamond fields last year.

The top producers of the stones by value last year were Botswana, Russia, Canada, South Africa, Angola and Namibia. Worldwide, gems worth $12 billion were sold, a 45 percent increase on 2009, the Kimberley Process tables show.

Global rough diamond production rose 39 percent in 2010 and the average price per carat increased 30 percent, Rapaport said in an e-mailed statement today.