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 coal producer Patriot Coal (NYSE: PCX) sank 12% on Tuesday after its quarterly results and outlook disappointed Wall Street.

So what: Driven largely by higher metallurgical, steel-making coal costs, and a mine waste treatment charge, Patriot Coal posted a quarterly loss of $12.4 million, or $0.14 per share, versus the average analyst estimate of a $0.07 per share profit. The shares had run up about 15% over the past month, so today's results -- representing its 12th straight quarterly loss -- come as an extra-big disappointment to Mr. Market.

Now what: Investors should expect more short-term pain. While Patriot is actively focusing its attention on met coal, management noted that new mine openings, higher labor costs, and sales-related expenses will significantly raise its production costs. Of course, given China and India's voracious appetite for steel, today's plunge in Patriot shares might be providing a solid long-term opportunity.

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