How can I tell if jewelry is gold or not?

In the United States, anything that is not at least 10 karats (42 percent gold) cannot be legally sold as gold. Anything that you purchase that is real gold should have the karat amount stamped into the jewelry. On rings, the stamp will be on the inside; and on necklaces and bracelets, the stamp will usually be somewhere on the clasp.
If the jewelry you are purchasing doesn’t have a stamp stating that it’s 10k, 14k, 18k, or 22k, chances are that it isn’t real gold.
If the jewelry is stamped and you still question whether or not it is real gold, you can take it to certain jewelers to find out whether or not it is real gold. A jeweler will be able to perform a chemical test or look at the piece under a jeweler’s loop to determine the quality of the piece.
If you’re thinking of purchasing a piece of gold jewelry and something is making you question whether or not it’s real, it’s probably best to pass and find another piece that you can feel confident about.
The best way to tell the purity of gold is by purchasing a Nitric acid test kit; such a kit can be found on sites like E-bay for under $30. It will cover karats ranging from 10 karat to 22k karat, as well as silver & platinum! Markings on a piece are usually completely useless — the amount of jewelry that’s improperly marked is absurd. If you’re not buying from a reputable jeweler, I strongly suggest using the Nitric acid test kit.