Silver mining in Arizona

Silver mining in Arizona was a powerful stimulus for exploration and prospecting in early Arizona. Cumulative silver production through 1981 totaled 490 million troy ounces (15 million kg). However, only about 10% of Arizona's silver production came from silver mining. More than 80% of the state's silver was a byproduct of copper mining; other silver came as a byproduct of lead, zinc, and gold mining.

Silver ore was first discovered in west-central Arizona in 1583 by Spanish explorer Antonio de Espejo, but no mining resulted. Again in 1598, Juan de Oñate led another expedition searching for Espejo’s silver; many claims were staked, but the expeditioners returned to Santa Fe without mining any silver, and the deposits remained unexploited. Espejo’s silver discovery is thought to be at the site of present-day Jerome, which later became a major copper-mining district.

Father Eusebio Kino, in charge of the Spanish missions in southern Arizona from 1687 to 1711, noted a number of “minas” in the mountains bordering the Santa Cruz valley (present Santa Cruz County, Arizona), but the Spanish word “mina” can mean either a mine or an unexploited mineral deposit. A noted silver discovery in 1736 at Planchas de Plata, Sonora, just south of the present Arizona/Sonora border drew attention to the silver potential of the area. Later Spanish documents record mining in the 1770s in Quijotoa, Aribac, and Arivaca, in southernmost Arizona. Mining was held back because Arizona was the northern fringe of the Spanish frontier, and plagued by guerilla war with the Apaches.

When southern Arizona became a United States possession by virtue of the Gadsden Purchase of 1853, American prospectors and investment started mining silver deposits previously known to the Spanish and Mexicans in present Santa Cruz and Pima counties. The Santa Rita mine in the Santa Rita Mountains and the Heintzelman mine in the Cerro Colorado Mountains both started in 1856, the Mowry mine in the Patagonia Mountains started in 1857, and the Salero mine in 1858.

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