You can also use density to determine the amount of gold found in a piece of jewelry. Gold alone is too soft to use in the making of jewelry, so it is often mixed with copper to make it stronger. This mixture is called an alloy. The gold alloy is not worth as much as pure gold. To determine how much copper is in the gold alloy, you must first find the mass of the jewelry. Then, measure the volume of the jewelry using the water displacement method due to its irregular shape. When the mass is divided by volume, density can be determined. If a piece of jewelry is 50% copper and 50% gold, its density would be 12.22 g/cm³. If its density is less than this, it would have more copper in it than gold and the value would be lower. If its density is more, there is more gold in it than copper and the value would be higher.