Your sweetheart just gave you a brand-new gold heart pendant and chain and told you that it costs hundreds of dollars and is made of pure 14 karat gold. You really appreciate the gift, but somewhere in the back of your mind you wonder, "How do I know that this chain isn't just gold-plated?" There are many ways to tell. Try out these methods (some will require you to handle the chain a bit roughly) and put your mind at ease.
Look for the letters G.P. or G.E.P. embossed somewhere on the chain. These letters stand for "Gold Plated" and "Gold Electroplated," respectively. According to Antoinette L. Matlins in the book "Jewelry and Gems: A Buying Guide," by law, a legitimate gold jewelry manufacturer must indicate whether the jewelry is gold-plated somewhere near the manufacturer's trademark.
Observe any skin discoloration that you may experience. Gold that has been mixed with large amounts of nickel or that is plated over nickel can eventually cause the skin to become discolored because many people are allergic to nickel and other metals. Pure gold is hypoallergenic and does not cause this reaction.
Observe any change in the color or brightness of the chain over time. Gold is heavier than most metals and over time, the gold plating of a piece of jewelry does not "wear off," as is commonly thought, but instead recedes into the jewelry as other metals rise to the top.
Hold a magnet up to the gold chain. Observe the reaction of the chain to the magnet. If the chain is attracted by the metal, then it is most likely gold-plated. Pure gold is not magnetic.
Have your chain professionally tested. This will require some expense, but it is the surest way to know if you have high quality gold. Take the chain to a jeweler and ask to have it tested and examined. The jeweler can perform numerous tests, including weighing, plate testing and nitric acid assay (the most accurate test. The jeweler should be able to perform any test without noticeable damage to the jewelry.