This folder contains correspondence relating to the mining and assaying of gold and other ores. After abandoning his interest in platinum in 1880, Edison attempted to use his ore separation inventions to recover gold from tailings. He also continued to correspond with numerous individuals who were interested in, or knowledgeable about, mines.

Approximately 30 percent of the documents have been selected. Correspondence from individuals associated with Edison, letters containing significant marginalia, and letters that are parts of important chains of correspondence have been selected. Correspondence with routine marginalia or with no marginalia has not been selected. Included in the category of routine marginalia are acknowledgments of the receipt of ores, inquiries regarding lost or unmarked shipments of ores, requests to send ores for assay, and notes about the results of assays (primarily in the hand of Edison's chemist, Alfred Haid).