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 miner Molycorp (NYSE: MCP) gained as much as 16% today on heavy volume.

So what: Today's news was a joint venture agreement with Japan's Hitachi Metals that will put Molycorp closer to its goal of doing more than just mining rare earths. The JV would produce rare-earth magnets that could be sold to a variety of industries including technology, health care, and alternative energy. For Molycorp, the move fits with a strategy that it calls "mine-to-magnets."

Now what: It's all very exciting with Molycorp -- the upcoming reopening of its Mountain Pass mine, the lingering questions about the supply of rare earths coming from China, and, of course, the soaring share prices of Molycorp and rare-earth-related investments like Rare Element Resources (AMEX: REE) and Market Vectors Rare Earth/Strategic Metals (NYSE: REMX). Of course, it's also all very speculative as investors bet on unpredictable policies from the Chinese government and a company (Molycorp, that is) that has managed a cumulative $84 million loss on $22 million in revenue since 2008. Could this work out for investors? Sure, just as any gamble has a chance of paying off. For those looking to invest though, Molycorp is a solid pass.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his Motley Fool CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy assures you no Wookiees were harmed in the making of this article.