Sterling silver is a metal alloy defined by its high purity, consisting of 92.5% silver and 7.5% other metals, typically copper. Genuine sterling silver is not magnetic. Since neither silver nor copper are attracted to a magnet, the resulting alloy also lacks magnetic attraction. This non-magnetic characteristic is a reliable indicator that can help distinguish authentic sterling silver from counterfeits or base metals.
Defining Sterling Silver’s Composition
Sterling silver is internationally recognized by its minimum millesimal fineness of 925. This designation means that 925 parts out of every 1,000 parts of the alloy are pure silver, often marked on jewelry as the “925” stamp. The remaining 7.5% is composed of other metals, added primarily to increase the material’s hardness and durability. Pure silver is naturally soft, making it impractical for everyday items like jewelry and cutlery.
The metal most commonly used to complete the alloy is copper, which strengthens the silver without compromising its color or luster. Other metals are occasionally included in the remaining 7.5%, such as zinc, germanium, or nickel. While copper is the standard choice, the overwhelming proportion of pure silver dictates the primary physical characteristics of the final sterling alloy.
The Science of Non-Magnetic Metals
Materials that are strongly attracted to a magnet, such as iron, nickel, and cobalt, are known as ferromagnetic materials. Ferromagnetism occurs when a material contains unpaired electrons that align their magnetic moments to create a powerful overall magnetic field.
Silver and copper do not possess these unpaired electrons, which is why they do not exhibit ferromagnetism. Instead, both metals are classified as diamagnetic. Diamagnetic materials react to a magnetic field by creating a very weak opposing force, meaning they are slightly repelled by a magnet rather than attracted to it. This slight repulsion is so minimal that a silver item will not visibly stick to a standard household magnet.
When Sterling Silver Appears Magnetic
Although genuine sterling silver should never strongly attract a magnet, a piece may sometimes appear magnetic due to manufacturing factors. One common reason is the presence of magnetic metals in small, functional components. Clasps, pins, or hinges often contain steel or other ferrous metals for increased durability, which readily attract a magnet.
Another factor is silver plating over a magnetic core. Items that are not solid sterling silver are made of a base metal, like steel or a nickel alloy, covered with a thin layer of silver. If a magnet strongly adheres to the main body, it indicates the piece is plated and the underlying metal is ferromagnetic. Trace amounts of iron contamination can also be introduced during manufacturing, leading to a weak, localized magnetic response.