Gem Diamonds has reported record earnings for the first half of 2011, with the company's EBITDA reaching $90.8 million – an increase of 489% over H1 2010.

The mining company's H1 revenue stood at $196.5 million, compared to $103.9 million for H1 2010, and the amount of cash from operating activities in the half totaled $101.2 million, as opposed to $27.9 million in H1 2010.

The first half also saw record per-carat figures, with the company's Letseng diamond mine realizing an average per-carat price of $3,052/carat – nearly double the average $1,728/carat Letseng diamonds fetched in 2010. The Letseng mine also yielded 295 rough diamonds that exceeded 10.8 carats in size and 105 stones with a per-carat value of over $20,000.

The Ellendale mine in Western Australia also saw record per-carat figures, with its fancy yellow diamonds achieving an average price of $4,045/carat (compared to $2,588/carat in H1 2010.)

Gem Diamonds CEO Clifford Elphick noted that the company's new pricing agreement with Tiffany & Co for its Ellendale yellow diamonds has resulted in average prices jumping 52.1% from January-June 2011. In addition, Elphick said, lower stocks of rough product in cutting centers and strong demand for diamond jewelry in India and China had resulted in record rough diamond prices, which were reflected in the prices of polished diamonds.