There are several ways to identify genuine silver coins, based on the physical properties of silver. Common non-damaging methods involve testing the coin with ice or magnets, observing its weight, or identifying the sound it makes when struck. Silver coins may also be identified with acid or bleach tests.
Silver is paramagnetic and exhibits extremely weak magnetism, so one way to test its authenticity is with a very strong magnet, such as a neodymium magnet. True silver will not easily stick to even a very strong magnet. Real silver also exhibits diamagnetic traits, which cause it to repel from magnetic fields. If placed on a magnetic bar held at a steep incline, true silver will slide more slowly than fake silver, due to its diamagneticism.
Silver can also be identified by its conductive properties. Silver is the best heat conductor of all metals. To test the genuineness of silver, place a piece of ice on the metal. If the silver is real, the ice will start melting immediately, and will fully melt much more quickly than ice placed on a non-silver metal in the same environment.
When two authentic silver coins are tapped together, they produce a high-pitched bell-like chime at a frequency of approximately 6145 Hz. One can test the authenticity of a coin by tapping two known silver coins together, and then tapping a known coin with the coin that is being tested and comparing the resulting sounds.
Silver coins can also be tested with bleach or acid, though doing so may harm the patina of the coin. Authentic silver tarnishes rapidly when exposed to bleach. If a silver coin is touched with a drop of bleach, the bleached area will rapidly turn black. However, this test only verifies the coin's plating and does not verify the silver content of the coin's core. Silver coins can also be tested with an acid test, in which the coin is scratched and a drop of acid is applied. The acid will change color, revealing which material the coin is made of.