Karat: A unit of fineness that measure the percentage of gold in 24ths. Pure gold is designated 24K and is much too soft to be used in jewelry except as a decoration. If your jewelry is 14K gold (the standard fineness in the U.S.), it means that it is 14/24 parts gold and 10/24 parts base metal. Rings, particularly men's rings, are often 10K gold due to it's higher durability. The purest form of gold used in jewelry is 18K. It was often used in ancient cultures as a symbol of wealth and royalty.