Gould & Curry Mill, Virginia City, Nevada, in 1868 photo by Timothy O'Sullivan. By the...

Gould & Curry Mill, Virginia City, Nevada, in 1868 photo by Timothy O'Sullivan. By the 1870's, precious metal ores were crushed and processed to extract the silver and gold in various 'amalgamation' processes. The most common 19th century method did not work on the Comstock silver sulfide ores. Instead, it required an old Spanish process, in which crushed ore was mixed with salt, water, copper sulfate, and mercury. The was then given additional grinding, during which the silver sulfides oxidized. The silver could then be recovered with the common amalgamation process using mercury (BSLOC_2020_1_43)