LONDON -- The attempt by Glencore (LSE: GLEN.L) to take over Xstrata (LSE: XTA.L) and create one of the world's largest mining and resources operations looked to be done and dusted. But the deal, valued at 16.9 billion pounds, is up in the air again after another of Xstrata's largest shareholders has joined those who want a better offer.

Standard Life and Schroders have already said they will vote against a deal unless they are offered more, and they have today been joined by Qatar Holding, Xstrata's second-largest shareholder with 10.3% of the company. Qatar Holding wants the current offer of 2.8 Glencore shares for every Xstrata share upped to 3.25 shares, and it could be enough for Glencore to take notice.

Under U.K. takeover rules, the opposition would need to garner 16.5% of the share capital in order to block the bid, and dissenters together now represent 13.3%. Glencore itself is not allowed to use the portion of Xstrata's shares that it already owns in any vote.

A nice opportunity?
What does that mean for shareholders? Well, Xstrata's shares are currently trading at 775 pence, which is the equivalent of 2.65 times the current Glencore price of 292 pence. And that means there could be a nice arbitrage opportunity here, at either the current offer or at the level now being demanded by Qatar Holding.

Suppose you buy one Xstrata share now at 775 pence. If the bid goes ahead at the original offer, you'll get 2.8 Glencore shares, currently valued at 818 pence, or 3.25 shares at the level of the new demand for a value of 949 pence. You'd be 6% ahead at the original offer, or 22% ahead if the new demand for 3.25 shares comes off -- or somewhere between the two if there's a compromise deal. And that looks pretty good.

However, it all depends on the deal going ahead, and Glencore could just walk away from it; it might not want to acquire strong, dissident shareholders, and there are disagreements by Qatar Holding over executive pay terms, too. But if it wants to stick to the current timetable, Glencore has until Thursday to hammer out a deal, and City commentators seem divided over the prospects of either a deal sweetener or a collapse of the whole deal.

It's an uncertain sector
There are plenty of uncertainties in the mining sector at the moment, with all the big miners having seen their share prices fall: BHP Billiton, Anglo American, and Rio Tinto are all down about 30% over the last 12 months, and that could swing things either way.

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But do you have the nerve to take a punt on Xstrata?

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