<p>The world’s biggest exporter of thermal coal is believed to be considering offloading some of its mines in New South Wales amid renewed activity among mining companies to test the worth of their assets.</p> <p>The <em> Australian Financial Review</em> reported this morning (Wednesday, September 6) that Xstrata had begun reviewing a portfolio of its Hunter Valley mines which could be worth up to $400m. </p> <p>US energy giant Peabody Resources bought Excel Coal, one of Xstrata’s rivals in the Hunter Valley, for $1.8bn in July. </p> <p>The largest of Xstrata’s mines, at West Wallsend west of Newcastle, makes up about three-quarters of the 55m tonnes of reserves the portfolio is said to include.</p> <p>It comes less than a month after Xstrata unveiled a four-year, $600m plan to upgrade its facilities and bring new projects online.</p> <p>The company is spending $350m on its Blakefield mine, $91m upgrading its Liddell mine to a 6m tonne annual production and about $200m on expansions to its Ulan and Glendell projects.</p> <p>The port of Newcastle is expanding to a third coal terminal, worth about $530m, from 2009 to be able to handle another 30m tonnes of coal each year from mines in the Hunter Valley and from as far inland as Gunnedah. </p> <br />