Falling copper prices hurt Freeport-McMoRan (NYSE: FCX) in the third quarter, the company announced today.

Profits were down 33% as net income slipped from $775 million in the third quarter a year ago to $523 this year. Profits were a $1.42 a share (excluding one-time items), falling short of the $1.45 expected by analysts.

The stock is down about 5% in trading as of 3 pm, to $34.85.

An analyst quoted on Bloomberg, Kerry Smith of Haywood Securities Inc. in Toronto, said that while lower copper prices won't force the company to close mines immediately, it could do so if copper prices stay low or even keep falling over the next few months. The cost of operating mines has been rising, and Freeport may close higher-cost mines in the coming year if prices do not recover.

Freeport has also announced that it will suspend a stock buyback program. It had bought $500 million in stock in the third quarter at an average price of $79.15 per share, more than twice the current stock price.

The market for copper is extremely unsettled right now. The big question is how severe the global economic slowdown will be, and how long it will last. A long slowdown will likely send copper prices even lower. So while some (including the irrepressible Jim Cramer) are arguing that this represents a buying opportunity, it may just be a point along a long downward fall.