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 rare-earth metals producer Molycorp (NYSE: MCP) had a rare down day on Thursday, sinking as much as 12% on extraordinarily high volume.

So what: According to, Byron Capital Markets analyst Jon Hykawy opined yesterday that the price of certain rare-earth metals -- lanthanum and cerium -- could fall hard, suggesting a looming risk to Molycorp's profitability. It's tough to tell whether that Wall Street call is the main driver of today's heavy sell-off, but with Rare Element Resources (AMEX: REE) and the Market Vectors Rare Earth/Strategic Metals ETF (NYSE: REMX) also down big, investors certainly seem concerned about something.

Now what: This is obviously one price plunge that isn't worth pouncing on. Even with today's double-digit loss, Molycorp is up more than 300% since its July IPO and still sports an almost unbelievable $4.5 billion market cap. In other words, the stock has a lot more room to fall before it becomes even a reasonable speculation.

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

Fool contributor Brian Pacampara owns no position in any of the companies mentioned. Try any of our Foolish newsletter services free for 30 days.

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