LONDON (Dow Jones)--Compania Minera Dona Ines de Collahuasi SCM, in which Xstrata PLC (XTA.LN) has a 44% interest, Thursday announces a revised mineral resource estimate with significantly improved confidence levels and an increase to total mineral resources and ore reserves. MAIN FACTS: -The new measured, indicated and inferred resource estimate totals 7.094 billion tons at an average grade of 0.82% copper and 269 parts per million, or ppm, molybdenum, using a 0.34% copper cut-off grade; This represents 58 million tons of contained copper metal. -The total tonnage of the mineral resource has increased by 40%, the equivalent of over 2 billion tons, compared with the estimate published in December 2009 and taking into account the 47 million tons mined during the first six months of 2010. -Increase is the result of new drill results, modeling changes and metal price assumption adjustments. -Mining reserves have increased by 315 million tons to a total of 2.453 billion tons at a grade of 0.82% copper compared with December 2009. -Progressing with concept studies into the alternatives to expand Collahuasi's operations to ultimately produce more than one million tons of copper annually, with the view to completing the studies in the first quarter of 2011 prior to a decision on moving into the pre-feasibility study. -Anglo American also has a 44% share in Compania. -Xstrata shares closed Wednesday at 1044.5 pence valuing the company at GBP30.7 billion. Anglo American shares closed Wednesday at 2539.5 pence valuing the company at GBP33.5 billion. -By Ian Walker, Dow Jones Newswires; 44-20-7842-9296; [email protected] (END) Dow Jones Newswires July 29, 2010 02:29 ET (06:29 GMT)