By Susan Orr of the Courier and Press

Aluminum maker Alcoa will permanently close its Warrick County smelting operations by the end of March, the company announced Thursday.

Some 600 people work at Alcoa's Warrick smelter, which has a capacity of 269,000 metric tons. Warrick's rolling mill and power plant, which employ another 1,235 people between them, will continue to operate.

In a statement issued after the news release, John Martin, Alcoa's vice president of U.S. smelting operations, said: "Although our employees have worked diligently through these challenging market conditions, the aluminum smelter at Warrick Operations is no longer competitive. The price of aluminum in the last year alone dropped about 30 percent. Our focus now is on our employees, and we will be working with our union, community and other stakeholders to help minimize the impact during this very difficult transition."

Most of Alcoa Warrick's hourly employees are represented by United Steelworkers Local 104. The Courier & Press was unable to reach Local 104 by email or phone late Thursday.

Alcoa blamed market conditions for the shutdown, noting that the Midwest transaction price for aluminum dropped approximately 30 percent in 2015. During that same time the Alumina Price Index fell approximately 40 percent, Alcoa said. Alcoa produces both aluminum and alumina. Alumina is a raw material in the production of aluminum.

The move is the latest in a series of similar steps Alcoa has taken in the past year in an effort to reduce its costs.

In March, the company announced that it was beginning a 12-month review of its smelting and refining operations "for possible curtailment or divestiture."

Since then, Alcoa has taken the following actions at its smelters:

Curtailed 74,000 metric tons of smelting capacity in Sao Luis, Brazil

Closed its 96,000-metric-ton smelter in Pocos, Brazil, which had been curtailed since May 2014.

Curtailed its Intalco and Wenatchee smelters, both in Washington State. The two operations had a combined capacity of 373,000 metric tons.

Announced it planned to curtail its Massena West smelter and permanently close its Massena East smelter, both in New York. Shortly after that announcement, Alcoa said it had reached an agreement with the state of New York for an incentives package to keep the Massena West smelter open. Massena West has a smelting capacity of 130,000 metric tons.

Once the Warrick smelter closes, Alcoa's only active North American smelter will be Massena West.

Since March 2015 Alcoa has also curtailed or closed 3.3 million tons of refining capacity, including 810,000 metric tons of refining capacity at its Point Comfort, Texas operations. Alcoa made the Point Comfort announcement at the same time it announced the Warrick smelter closure.

So what exactly is a smelter, and how will Alcoa Warrick Operations function once it closes its smelter?

Aluminum smelting is the process of extracting aluminum metal from aluminum oxide, which is also called alumina. This is done through a chemical process involving heat and electricity.

The aluminum produced at Warrick is cast into ingots, which are cooled and then sent to a rolling mill — a sort of industrial-sized series of rolling pins which flatten the ingots into thin sheets of aluminum. Those sheets get rolled into large coils that are then sent elsewhere for use in food and beverage cans, pop-top can tabs and lithographic printing plates.

An on-site power plant provides electricity for Warrick Operations.

After the Warrick smelter shuts down, the facility will purchase aluminum made elsewhere for use in its rolling mill.

According to Alcoa's website, Warrick Operations is one of the largest aluminum smelting and fabricating facilities in the world. The property, which includes more than 9,000 acres, is located along Indiana 66 between Newburgh and Yankeetown, Indiana.

The first molten metal at the Warrick site was poured in June 1960.

Alcoa issued its Warrick announcement after the close of stock trading Thursday. Shares of the stock closed at $8.27 on the New York Stock Exchange, down 34 cents (4 percent) from the previous day's close.