When shopping for precious stones, it is important to keep in mind the specifications which are used to judge the quality of the stones. Diamonds and gemstones are evaluated by a universal standard that is known as the "Four C's." Cut, clarity, color, and carat weight are the most important technical features of any precious stone. A certified jewelry dealer should reveal all of this information to customers. Without specialized optical equipment, it is difficult for a person to judge a diamond or gemstone and use the Four C's standards. Additionally, a GIA certification implies that a precious stone is authentic and meets the criteria that is used to market such jewelry.