The term GOLD UNIT refers to a variety of units used to measure gold. An INGOT is a block or BAR of gold that is usually cast into a specific shape for storage and transport. A CARAT is a unit of weight used to measure the purity of gold, with 24 carats being pure gold. An OUNCE is a unit of mass used to measure gold, with one troy OUNCE equaling 31.1 grams. A BAR is a unit of gold that is usually rectangular in shape and is often stamped with its weight and purity. Karat is a unit of purity used to measure gold, with 24 karats being pure gold. Finally, a NUGGET is a small piece of gold found in nature.