The write-downs aren't done yet: Glencore Xstrata – $7bn

Since the Glencore Xstrata merger in May accountants have been reviewing Xstrata assets and the results are not pretty: According to industry sources who spoke to Reuters, the company is set to write-down about $7 billion of the coal and nickel miner's assets.

The major hit – about $5 billion – will come from nickel operations in New Caledonia, mainly due to low commodity prices. Nickel has lost as much as one-third of its price since 2007.

When the company releases its half-year earnings report on Tuesday it will be the first time investors see a full set of results from the May takeover.

Last week Glencore published production numbers for the half-year showing output in line with forecasts, including a 1% increase in nickel and a 4% rise in coal operations compared to the first half of 2012.

The miner also saw a 20% increase in copper output – an area which the company is actually trying to downsize. Last week rumours swirled that Glencore was close to selling its massive Las Bambas copper project in Peru to a Chinese aluminium group.

Monday's news did not fall on deaf ears: The company lost more than 2% on its share price on the London exchange. Year-to-date the group has seen a drop of almost 20%.

But Glencore is not the only mega-miner faced with a slew of write-downs. In fact, this $7 billion is not even the biggest: Barrick Gold booked an $8.7 billion impairment charge this quarter.

See the ten biggest write-downs of the summer here.