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 ceramics maker Ceradyne (Nasdaq: CRDN) rose 43% today after announcing the company will be purchased by 3M (NYSE: MMM).

So what: 3M will pay $35 per share for Ceradyne, for a total deal value of $860 million. The company will add $500 million in revenue to 3M and give it expanded reach in transportation and energy markets.

Now what: The acquisition is expected to be $0.01 accretive to earnings over the next year and I have to wonder about the steep price paid by 3M. Ceradyne has seen revenue fall and earnings plummet in the last two quarters so this doesn't seem like a slam-dunk at the current price. 3M may be able to expand the company's reach internationally, but I don't think this is any reason to buy 3M. For Ceradyne shareholders the stock is already trading near the purchase price so there's likely little upside in holding onto the stock after today.

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