What: Shares of Century Aluminum Co (CENX 1.81%) dropped as much as 17% on Tuesday after being downgraded by an analyst.

So what: BMO Capital analyst David Gagliano downgraded the stock to market perform from an outperform rating and slapped a $6 per share price target on the stock. The analyst did note that the company could continue to rally if aluminum prices rise, but felt that after the recent bounce the stock was fairly valued. 

Now what: The volatile week for Century Aluminum continues and this is why investors should be wary of speculating on a company that's losing money. Even bullish predictions are only that the company will turn a corner from burning cash to being slightly better than breakeven sometime early in 2016. But even then the price of aluminum could derail that prediction. In my eyes, this industry is too risky to bet on right now and until there's fundamental improvement in both supply and demand, investors will just be speculating on where the bottom is.