Answer: The kind of test that can be performed to make sure that you are not accidentally trying to sell a fool's gold (iron pyrite) is called the Acid Test.
Explanation: This Acid test is performed by making a little scratch on the gold and adding drops of a liquid nitric acid on that spot, after adding the nitric acid, if the spot turns green it is a fake gold but if the spot is unaffected, it is a real gold.