Bite gently into the material. Gold is a soft metal, while fool's gold is very hard. If you can easily leave an indention, the substance is most likely real gold.
Hold a magnet up to the material. Pyrite contains a high amount of iron, which will be attracted to the magnet. Pure gold will be unresponsive to the magnet.
Rub the material along an unglazed, porcelain tile. Fool's gold will make a black streak. Pure gold will leave a yellow or gold color.
Perform a density test by measuring the mass of the material on a mass scale. Then measure the volume by dropping it in a graduated cylinder half filled with water. The difference between the initial volume and the volume with the material added is the material's volume. Divide the mass by the volume to calculate density. Gold should have a density of 19.7 g per cubic centimeter. Fool's gold will be considerably less. This is also a good test to determine the purity of gold, as any deviation from 19.7 g/cm3 indicates the existence of other elements.