Glencore CEO Ivan Glasenberg smiles as he leaves after the company's annual shareholder meeting in the Swiss town of Zug in this May 9, 2012 file photo. Shares in mining and trading company Glencore fell almost 30 percent and closed at a record low on Monday over concerns it is not doing enough to cut its debt to withstand a prolonged fall in global metals prices.About 3.5 billion pounds ($5.33 billion) in market value was wiped off the Swiss-based firm, whose $10 billion share offering in 2011 turned its managers into billionaire shareholders but left it saddled with debt – a growing problem as commodity prices fell.