![]() And I thought everyone knew about Aqua-Regia and Gold to form 3HCl+1HNO3 or NOCl+Cl2+H OH pending temperatures, quantities and solution strength. Other reactions that are normal are the formation of AuCl3 or AuCl4 where excessive Chlorine is present. This is common in some areas of the country where high Sulfur Coal is burned such as the steel mills in Indiana. Gold reacts with Sulfur fairly readily to form Ag2S and is usually noted as a Br/Bk discoloration on Gold. It probably is possible to create an "artificial patina" on a pure gold coin, but you'd need (a) some pretty noxious chemicals, (b) some high-tech gear, and/or (c) a lot of very expensive trial and error. Gold so impure that a "real patina" readily forms has rarely been used as a coinage metal. ![]() 900 fine alloy used for American circulating gold coins, can discolour slightly because the copper in the alloy can form a patina. As a result, pure gold doesn't form a patina. Indeed, it is quite resistant to most kinds of chemical attack. ![]() Gold is one of the few metals which is naturally resistant to oxidation at normal atmospheric temperature and pressure. All ancient coins need to be cleaned after they're dug out of the ground, but an ancient coin which has had it's patina completely stripped away to reveal the bare metal underneath is considered to have been overcleaned, and not as desirable as a coin with it's patina intact.Īlso can you get Patina on gold? If so, how do you get it? On ancient coins, patina is inevitable, and depending on the composition of the coin, the patina can be quite thick. On older coins and coins from circulation, patina is considered normal and natural, and it's removal (by "cleaning") is generally frowned upon by coin collectors. On such coins, "patina" would be regarded as a sign of poor storage, environmental damage (such as water or fire) or an attempt at creating artificial toning. On modern proof and uncirculated coins, patina shouldn't have had time to form yet, especially if the coins have been stored properly. That depends on what kind of coin we're talking about. The formation of a patina is the natural consequence when a piece of refined metal (such as a coin) is kept in an oxygenated environment (like the open air) for a prolonged period. Being bright and shiny is not the natural state for most of the metals your coins are made up of.
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