You can check the density by filling a graduated cylinder with water and checking the volume then adding the unknown metal and seeing the change in volume. make sure you get the mass of the metal in grams first. Calculate the density by dividing the mass of metal in grams by the volume in milliliters.
Compare this number to the standard density of gold, which is 19.32 grams per milliliter. If your calculated density is very close to the standard density.