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-earths miner Molycorp (NYSE: MCP) climbed as high 17% on Friday after investors applauded its quarterly results and new supply agreement.

So what: Plenty have feared that soaring rare-earth prices have reached dangerous bubble territory, but Molycorp's second-quarter profit beat -- $0.52 per share versus the Wall Street consensus of $0.40 -- suggests that the trend isn't turning anytime soon. In fact, the company also announced a new supply agreement with Hitachi Metals, further reinforcing those strong demand tailwinds in investors' minds.

Now what: Molycorp remains too speculative for most Fools. While CEO Mark Smith noted that the global demand for rare-earth minerals continues to be "very high, and supply outside China continues to be tight," Molycorp's valuation seems to already have plenty of optimism baked into it. Given Molycorp's price-to-sales ratio of nearly 80, a decent return seems questionable even if rare-earth prices remain strong.

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