As a member of our 10% Promise team, I see a lot of wild swings in the market. Sometimes there's an easy explanation and sometimes the market knocks us for a loop without telling us why. But every week I learn something new. Here are a few things from this week.

Rare-earth elements are still hot
Just last week, I finally came to the conclusion that this rare-earth bubble wasn't going to pop. This week, Molycorp (NYSE: MCP) jumped again on news of a joint venture with Hitachi Metals to make rare-earth magnets.

There doesn't seem to be anything but good news coming from Molycorp, but if you're looking for another way to invest in the sector, Rare Element Resources (AMEX: REE) is another up-and-coming play. Even though it's still a speculative investment, the rare earth space hasn't shown any signs of cooling down.

When does it end? I have no idea, but I've learned that being anything but bullish on rare earth stocks is a futile endeavor, for now.

I should still be cautious in China
Shares of L&L Energy (Nasdaq: LLEN) were pummeled on Herb Greenberg's battering of the company. The Securities and Exchange Commission is apparently investigating some accounting statements of small Chinese companies that trade in the U.S. via reverse mergers. Whether it is allegations of unreliable accounting statements and fraud or dilutive stock offerings, I'm never surprised when a Chinese company hits our plunged list. If I could make this caution flash in bright lights, I would. Buyers beware!

A double overnight
It's like seeing a unicorn or Santa's reindeer on the rooftop, but this week, we saw a double overnight. Shares of InterMune (Nasdaq: ITMN) were up 140% on a positive drug recommendation in Europe. The drug business is full of pops and plunges, but more than a double overnight was quite a sight. If only I could predict the next time it will happen.

Knowing the rules is still half the battle
There was more confusion about dividends again this week, and I've learned I'm still no expert. China Digital TV (NYSE: STV) declared a special dividend of $2.00. As we learned last week with optionsXpress's (Nasdaq: OXPS) special dividend, Nasdaq Rule 11140(b)(2) applies to special dividends greater than 25% of a stock's market capitalization, affecting the date on which shares trade ex-dividend. But because this dividend was split into two $1.00 dividends, and because the company is traded on the New York Stock Exchange, Nasdaq rules don't apply.

But here is what we should take away from this. It's important to understand the difference between the ex-dividend date and the record date for a dividend. The ex-dividend date is the first day a stock trades without dividend (and the stock price should adjust downward accordingly), while the date of record is usually two days after the ex-dividend date (I say usually because we saw a special case last week). This is because it takes time for exchanges to clear trades, so if you owned the stock overnight before the ex-dividend date, you would indeed be a holder of record two days after the ex-dividend date.

Also, take note that special dividends are treated differently than regular dividends for other purposes, such as option exercise prices. You may want to do some research if a stock you own declares a special dividend; it could save you some money.

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Fool contributor Travis Hoium does not have a position in any company mentioned. You can follow Travis on Twitter at @FlushDrawFool, check out his personal stock holdings, or follow his Motley Fool CAPS picks at TMFFlushDraw.

China Digital TV Holding is a Motley Fool Rule Breakers recommendation. optionsXpress is a Motley Fool Stock Advisor selection. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.