Planchas de Plata, Sonora

Planchas de Plata (Spanish for slabs of silver), sometimes called Bolas de Plata (balls of silver) is a historic silver-mining district near Nogales, Sonora, Mexico, and a few miles south of the border with the US state of Arizona.

Native silver was discovered here in 1736 by Antonio Siraumea, a Yaqui Indian, on the Rancho Arizona of Bernardo de Urrea.

Toward the end of last October, between the Guevavi Mission and the ranchería called Arizona, some balls and slabs of silver were discovered, one of which weighed more than one hundred arrobas (2,500 pounds), a sample of which I am sending to you, Most Illustrious Lord.

--Captain Juan Bautista de Anza to Bishop Benito Crespo, January 7, 1737.Prospectors and miners rushed to the area of the great silver discovery of October, 1736.

It was given the name San Antonio de Padua by Justicia Mayor Juan Bautista de Anza when he arrived on the scene in November and ordered that all the silver that had been taken from the site be impounded and brought to Urrea's Arizona Ranch, some fifteen miles down the canyon.