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 Alpha Natural Resources (NYSE: ANR) closed down more than 17% after adjusted earnings came in well short of estimates.

So what: Alpha, now the world's third-largest coal miner, booked $0.96 a share in second-quarter earnings after excluding costs related to its acquisition of Massey Energy and other special items. Revenue rose 59.3% to $1.59 billion. Analysts were looking for $1.12 a share on $1.47 billion in revenue, according to data compiled by Yahoo! Finance.

Now what: The selloff may be overdone. Only one month's worth of Massey's performance was included with the results, and pricing was already trending higher. In short: Earnings miss notwithstanding, all the reasons my Foolish colleague Christopher Barker liked Alpha in January appear to still be valid. Do you agree? Disagree? Weigh in using the comments box below.

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