Cazo process

This is a variation of the Patio and Cazo processes. Invented around 1860 at the Comstock mines, Nevada, and named after the district where it was developed. Mark Twain described the operations in his autobiographical novel Roughing It (Vol. 1, Chap. 36). 

Cazo [Spanish, a copper vessel] An ancient process for extracting silver from sulfide ores. The ore was boiled in a copper pot with salt and water addition of mercury gave silver amalgam. The copper served as the reducing agent. Described in 1640 by A. A. Barba who claimed that it had been operated since 1590. Around 1800 it developed into the Fondon process, in which the raw materials were ground together. 

Invented by Bartolome de Medina, a Spanish trader, in Mexico in 1554, and used there until the end of the 19th century. The invention changed the course of economic history in all Hispanic America 40 percent of all the silver recorded to have been produced in the world before 1900 was extracted by this process. See also Cazo, Washoe. 

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