Gold is measured in karats, abbreviated by the letter "k." Solid gold is considered 24k which is 24 parts gold. Legally, gold should be stamped with the karat weight. Inner shanks or rings, clasps of neckalces and bracelets, earring posts and backs usually have numbers ranging from 10k to 24k. Legally the lowest karat of gold that can be sold in the USA is 10k which is 10 parts gold and 14 parts other metals (alloys) to add color, strength and reduce price. 14k is 14 parts gold, 18k is 18 parts gold, etc...