The early history of the Globe-Miami district involved the development of large, low-grade, disseminated copper deposits.

The Miami smelter resulted from the need of refining the concentrates of the Miami Copper Co. and Inspiration Consolidated Copper Co. that operated mining properties in the area.

These porphyry copper deposits ores averaged 2.5 percent copper, including those from the Warrior Mine, Iron Cap Mine and Arizona Commercial Mine.

Early concentrates were sent to Cananea, Mexico, for smelting. However, the 1910 Mexican Revolution redirected ore shipments to the International Smelting and Refining Co.’s smelter at Toole, Utah.

Rising output from local mines and the completion of the Miami and Inspiration mills demanded a local smelter. The International Smelting and Refining Co. purchased 32 acres from the Miami Copper Co. to erect a smelter. Work started in 1913 with the grading for a railroad connection and necessary steel building components.

Louis D. Ricketts, the consulting mining engineer for Inspiration Consolidated Copper Co., was credited with having designed and constructed the Miami smelter along with the Arizona Copper smelter at Clifton-Morenci and the Calumet and Arizona smelter in Douglas.

Ricketts’ Miami smelter design was focused on efficiency, with the ability to create wire bars from 97 percent of the copper in the concentrates. Additional precautions were taken in transport, including the use of closed cars and specially housed spreading beds and belt conveyors to prevent the loss of fine concentrates to the desert wind.

Dust recovery during the copper- roasting operation proved successful through the installment of two Cottrell electrostatic treaters, the first used in Arizona.

“Blown in” at a cost of $3 million in 1915, the Miami smelter has been a landmark. It has stood the test of time involving multiple expansions, renovations and upgrades.

The following year, the Miami-Inspiration-Globe area surpassed copper production in Bisbee.

Upon the closure of the Old Dominion smelter in 1924, Miami’s International smelter assumed additional shipments, including those from the Arizona Commercial Mine.

Modifications within the next decade included a reverberatory furnace plant composed of four furnaces to further improve the smelting rate.

Acquired by Inspiration Consolidated Copper in 1960, the International smelter was expanded to handle heightened production including concentrates from the recently acquired Christmas Mine.

Copper production in 1962 reached 104.6 million pounds, the largest peacetime production at that point in the smelter’s history.

The smelter was updated in 1974 to meet Clean Air Act regulations. Cyprus Minerals Co. acquired the Miami open-pit mine and smelter in 1988, upgrading the smelter with an ISASMELT furnace during the early 1990s.

It was the first use of ISASMELT process in the United States. The ISASMELT process was developed to enhance the production of non-ferrous metals (not magnetic, corrosion-resistant metals lacking iron) such as copper, reducing copper-production costs while increasing smelting capacity.

Today, the Miami smelter, rod mill and open-pit mine are operated by Freeport-McMoran Copper & Gold Inc., producing 420 million pounds of copper and 725,000 tons of sulfuric acid annually used in the leach-solvent extraction-electrowinning (SX/EW process) of copper from oxidized ores and mine wastes.

It is one of only two smelters currently operating in Arizona. The other smelter is operated by ASARCO at Hayden.

The Miami smelter is the only one in the United States to receive the International Organization of Standardization (ISO) 9001:2000 certification for quality management.

The Miami smelter treats copper concentrates from Freeport’s mining operations in Arizona and New Mexico. It includes four Hoboken-style converters and one Inspiration converter.

Planned upgrades by 2017 to the smelter necessitated by recent EPA environmental regulations involve a company expenditure of $450 million. They include the ability to capture more than 99 percent of its SO2 emissions, while boosting copper production by 30 percent.

William Ascarza is an archivist, historian and author of seven books available for purchase online and at select bookstores across Southern Arizona. Email him at