Oct 19 (Reuters) - Gem Diamonds Ltd (GEMD.L) said it remained cautious ahead of the Christmas season even though the industry had seen retail demand stabilising in the important U.S. market, albeit at lower levels.

Gems from Gem Diamonds Ltd operations in Ellendale, Australia - Photo: www.gemdiamonds.com

The company said mining costs at its Letseng and Ellendale units continued to be hurt by the weakening of the U.S. dollar against the South African rand and the Australian dollar.

While prices of rough diamonds trended upwards during the third quarter, they still remain substantially below pre-September 2008 levels, it added.

Gem Diamonds said cutting centre stocks remained high, mainly due to lower U.S. imports of polished diamonds both from weaker retail sales and destocking within the country's diamond jewellery retail sector.

During the third quarter, the company recovered 23,756 carats of rough diamonds from Letseng and 58,611 carats from the E9 pipe at Ellendale.

Gem Diamonds said it had a strong balance sheet with $100.5 million in cash and no debt.

Shares of the company were up 1 pence at 248.70 pence at 0744 GMT on Monday 19 October on the London Stock Exchange. (Reporting by Aditi Samajpati in Bangalore)