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The proportions of silver and gold can vary widely. Doré bars weigh as much as 25 kg.
During the nineteenth-century gold rushes, gold nuggets and dust would be melted into crude gold bars mistakenly called "bullion" by miners. They were, more accurately, doré bars with higher contents of silver and other adulterants than mints of the world would accept. Mint and private assayers would then refine the doré bars to an acceptable purity, 999 fine, gold bullion, with the silver and base metals removed. By the time of the California gold rush, mints were moving away from the age-old process of cupellation to "part" bullion and moving toward the acid refining process developed by chemist Joseph Louis Gay-Lussac for the French mint. By the time of the Klondike gold rush, mints were replacing Gay-Lussac's acid process and introducing electrolysis to refine doré bars into 999.9 purity gold bullion.
Associated industry codes
According to the United States Census Bureau, the creation of doré bars is conducted at establishments engaged either in "Gold Ore Mining" (NAICS Code 212221), or "Primary Smelting and Refining of Nonferrous Metal (except Copper and Aluminum)" (NAICS Code 331419).
Derivation of the term
- Metallurgy of Gold, Silver, Lead and Zinc. Scranton, Pennsylvania: International Correspondence Schools. 1902. pp. 87–91. Retrieved 3 April 2020.
- "US Census Bureau". Census.gov. Retrieved 5 December 2018.
- "2002 NAICS Definitions: 212221 Gold Ore Mining".
- "2002 NAICS Definitions: 331419 Primary Smelting and Refining of Nonfe…".
- "Archived copy". Archived from the original on 2007-10-07. Retrieved 2007-01-02.CS1 maint: archived copy as title (link)