M & M Gold Exchange notes that jewelers and others have long used the same tests, including applying nitric acid and attempting to attach a magnet to a metal piece, to verify an item is made of real gold. In the United States, anything less than 10 karats is not considered real gold.
According to M & M Gold Exchange, the simplest way to test a piece of metal to see if it is gold is to attempt to attach a magnet to it. Gold is not magnetic. However, many of the metals used in fake gold jewelry and other objects are magnetic. Bear in mind that clasps and other parts of certain gold jewelry are often made of magnetic metal. Apply the magnet to the main portion of the piece to avoid making a mistake.
Hosts of the PBS television show "Antiques Roadshow" and their various experts frequently help guests determine whether family heirlooms and estate sale finds are real gold. They recommend applying nitric acid to residue from the object to check its authenticity. Do this by rubbing the object onto a piece of slate. Next, apply a small amount of nitric acid to the residual on the slate. If the acid completely dissolves the residual, the object is not likely gold. If any residual remains, it most likely is gold.