Sterling silver is an alloy, typically formed from 92.5% pure silver and 7.5% pure copper. Sometimes called “standard silver,” this alloy is the traditional metal from which useful and ornamental silver items are made. Products made from sterling silver include tableware and jewelry, which if made from pure silver would be too soft to use for the purposes for which they were intended. This characteristic malleability of pure or “fine silver” make it unsuitable for many purposes.
Fine silver is 99.9% pure silver and is regarded as pure silver. Used in silver bullion bars, fine silver may bear the stamped marking “999” or “.999 fine silver.” The number indicates the silver’s purity, according to a system developed for grading the purity of precious metals used as alloys. The “Millesimal Fineness System” is how precious metals, like silver, are identified in alloy mixtures. The number indicates the percentage of pure metal contained in the alloy by mass. So-called “three nines fine” silver is more valuable than any other type of silver, since it is the purest form of silver and, for all practical purposes, contains no other metals.
By contrast, sterling silver may be identified by the marking “.925,” showing the lower silver content that it contains. 92.5% silver items are still valuable, but their lesser silver content makes them less precious than pure fine silver. Additionally, sterling silver items may be plated with a coating of either .999% fine silver or the more expensive metal, rhodium. Rhodium is used to prevent the item from tarnishing, since items made from either pure or sterling silver will eventually acquire a blackened finish due to surface oxidation.
