There is a lot of confusion about the term "gold karat" when it comes to purchasing gold coins and bars. However, it is not as complicated as it may seem. Put simply, the "karat" of any gold coin or bar refers to the purity of the gold it contains and not the total amount of gold.
For instance, a one ounce Canadian Gold Maple Leaf coin is a 24 karat gold product and a one ounce American Gold Eagle coin is a 22 karat gold product. The purity of the Canadian Gold Maple Leaf is .9999 gold and the purity of the American Gold Eagle is only .9167 gold, but they both still contain one ounce of gold. The American Gold Eagle contains one full ounce of gold and the remaining material is made up of 3% silver and 5.33% of copper resulting in a more durable coin. Thus a one ounce American Gold Eagle's total weight and size is more than a one ounce Canadian Gold Maple Leaf. Also note that there is a distinct difference in the color between pure gold and alloyed gold where the presence of other metals "dulls" the gold luster.
Another good example is the $50 Mexican Gold peso. It is only 90% gold making it a 21.6 karat gold product, but contains 1.2057 ounces of gold because of it's larger size.
Understanding the karat (purity) of gold coins and gold jewelry is important so that you can determine the value of the gold content. For instance, a 10 karat gold ring that weighs 10 grams only contains 4.17 grams of gold where a 14 karat gold ring that weighs 10 grams contains 5.85 grams of gold. The table below shows the most common karats used to produce gold coins and gold jewelry.
||.417 Gold Purity
||.585 Gold Purity
||.75 Gold Purity
||.90 Gold Purity
||.916 Gold Purity
||.999 Gold Purity