OZ Minerals has rebuffed market rumours by confirming plans to start commissioning its $1.1 billion Prominent Hill copper and gold mine next month.

    Company chief executive Andrew Michelmore said in an announcement that there was no basis to rumours of a possible delay, which he said were "may be creating a false market in OZ Minerals' shares."Mr Michelmore said the South Australian mine would commence commissioning on October, once its crushing circuit comes into operation.

    The project is expected to produce between 110,000 and 120,000 tonnes of copper in concentrate and between 80,000 and 85,000 ounces of gold in 2009, OZ said.

    OZ, formed out of a merger between gold company Oxiana and zinc giant Zinifex, has suffered in the recent downturn in markets, with its share price falling from $3.34 on May 6 to yesterday's close of $1.44.

    Mr Michelmore noted the discrepancy in an announcement, saying it was well below a valuation of between $3.80 and $4.40 determined in an independent expert's report prepared in May.

    "One thing that is clear is that the inherent value of the Company's assets has not deteriorated in the four months since the Independent Expert's report was published," he said.