CNBC Stock Blog

Century Aluminum: End of the Alcoa Ride?

Chris McKhann|writer, OptionMonster

Shares of Century Aluminum are up 1,000 percent from their March lows, but at least one trader is looking for the stock to give some of that back.

CENX tacked on 11.5 percent yesterday to close at $10.76, following Alcoa's surge from its positive earnings surprise. That price is roughly 30 percent higher than just a week ago but remains below the August and September highs above $12.

OptionMonster's real-time systems show that more than 20,000 of the January 7.50 puts were bought, the largest block of 17,599 going for $0.60. Open interest at the strike was just 1,730 contracts, so the trade was clearly opening new positions.

A large block of CENX stock traded at roughly the same time, so this could have been a directionally neutral trade based on the belief that volatility will increase.

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Chris McKhann is an analyst and writer for .