Johannesburg - De Beers, the world's biggest diamond miner, this past week reported its highest ever half-year sales of rough diamonds following strong demand from the United States, China and India.

Sales were 33 percent higher at US$3.5 billion in the first six months of 2011, with the price of rough diamonds rising about 35 percent.

Net earnings surged to US$694 million from US$255 million a year earlier.

De Beers – with mining operations in Botswana, Namibia, South Africa and Canada - said it continued to focus on efficiency improvements and maintaining a lower, sustainable overhead base.

As at June 30, the company had free cash-flow of US$469m and had reduced its net debt by 27 percent from US$1.45b in 2010.

The miner produced 15.53 million carats of diamonds during the period. It said that the expansion of its flagship Jwaneng Mine in Botswana was progressing well, while it had completed an optimization study for Snap Lake Mine in Canada.

It also completed disposal of certain assets in South Africa, including sale of Finsch Mine to Petra Diamonds and Namaqualand to Trans Hex.

Owing to strong demand in the Middle East, Indian and Asian retail markets, De Beers continued expansion of its Forevermark diamond brand into China, Hong Kong and Japan.

The brand was recently launched in India, Singapore and the Caribbean.

During the six-month period, De Beers Diamond Jewellers opened shops in Beijing (China), Kazakhstan and Dubai (UAE).

The unit will open further stores in mainland China, as well as a second store in Hong Kong.

De Beers said it expected strong consumer demand seen during the first half of the year to continue throughout 2011, buttressed by the Christmas season, Diwali and the Chinese New Year.