Revett Mining Co. is closing the Troy Mine and laying off nearly 80 workers.

Plummeting copper prices are the main reason behind the move, according to John Shanahan, Revett president and chief executive officer.

Development work will end immediately and milling operations will continue until the end of January. Then the mine will be placed on “care and maintenance status,” Shanahan said in a news release.

“It’s a tough one, it really is. It’s not easy on anybody. It really hurts,” Shanahan said.

Shanahan cited the precipitous drop in copper prices. “We based our plans on a copper price of about $3 per pound,” Shanahan said.

Copper prices as of Monday had dropped to $2.57 per pound, the lowest in more than five years.

The mine currently employs 85 people; six to eight will remain working by the end of February.

The mine had closed in late 2012 due to underground rockslides. It reopened in November and since then produced 27,053 ounces of silver and 159,121 pounds of copper.

An additional 40,000 tons of ore will be processed through the mill before operations shut down.

Shanahan said Revett would reopen the mine if metals prices rebound.

In the interim, Shanahan said, the firm would focus on permitting efforts for the Rock Creek mining project.