Genuine silver (also known as sterling silver) is a beautiful and valuable material that will last for years if proper care is taken. Because it is a soft metal, silver alone cannot be used to construct jewelry, flatware or other durable items, so it is mixed with other metals. For an item to qualify as genuine silver, it must be 92 1/2 percent pure. Most sterling silver has 7 1/2 percent of some other metal, usually copper. Sometimes items are made of other metals and have a thin layer of genuine silver on top. This is known as silverplate, which can be rubbed off with use or wear. Like gold, silver must have a trademark noting its purity. Silverplated items do not have a "925 Silver" mark like items that are 100 percent silver.
Carefully inspect your item for a sterling silver notation. If you are looking at jewelry, check the clasp. You should see one of the following markings or something similar: "9.25," "925/1000," "Sterling," "S/S" or "Sterling 9.25." If you do not see any of these markings, it is highly unlikely that the item is genuine silver.
If you do not see the sterling marking, the item is probably silver-plated. Check the coloring of the item carefully. Genuine silver is generally less shiny and colder in tone than silverplate. If you see places where the silver appears to be flaking off or turning green, the item is silverplated.
To investigate further, you can try cleaning the item with a soft cloth: Real silver will usually leave black marks on the cloth. These marks are caused when sterling silver oxidizes. Exposure to air or other chemicals results in tarnishing that does not occur with fake silver.
If you suspect the item is made of stainless steel (as many types of flatware are), you could hold a magnet near the item. The magnet will be attracted to the steel.
If the item does have the sterling marking, yet you still suspect it may be fake, you can take the item to a pawn shop or jeweler for a professional to perform the "acid test." A small drop of nitric acid (a harsh industrial chemical) will turn a non-sterling item green because of its high copper content. Items that are silver-plated brass, nickel silver or low-quality silver will turn green. Be aware that nitric acid will leave a permanent discoloration on your item, so make sure it is applied in an inconspicuous spot.