Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of iron ore royalty trust Mesabi Trust (NYSE: MSB) fell as much as 16% in intraday trading Thursday on extraordinarily high volume.

So what: Mesabi Trust closed yesterday's trading down 6% (nullifying the gains from earlier in the day), but apparently Mr. Market wasn't quite done with the sell-off. It's tough to know what exactly is driving this heavy punishment, but when you consider Mesabi Trust's volatile nature (a beta of 1.8), exposure to commodity prices, and the fact that its stock has more than doubled over the past six months, big drops shouldn't be a big surprise.

Now what: Investors should see this weakness as a possible income opportunity. Without any big company or industry-related news, I'm taking the latest move as part of the normal stress that comes with such a volatile stock. You might want to diversify your iron ore bet with Vale (NYSE: VALE), BHP Billiton (NYSE: BHP), and Rio Tinto (NYSE: RIO), but Mesabi is a proven outperformer at least worth looking into.

Interested in more info on Mesabi Trust? Add it to your watchlist.

Fool contributor Brian Pacampara doesn't own a position in any of the companies mentioned. Try any of our Foolish newsletter services free for 30 days.

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