At least 95% of the surface of the pearl is immaculate, with the remaining 5% having little concentrated flaws. AAAA High-Grade Tahitian pearls account for the top 5-10% of the pearl harvest and may be purchased in premium jewelry retailers. Tahitian pearls account for only 2% of the world's pearl crop. They are known for their rich color, intensity, and durability and can sell for up to $100 per bead. Pearl quality is based on a scale of A to E; the higher the grade, the better the pearl. These pearls are used for jewelry items that will not be worn often or washed frequently. They are most commonly found in strands or pendants but can also be found single. Pearl grades are determined by a grading table developed by the International Pearl Association (IPA). The IPA grades pearls from A to E according to physical defects they contain. Grade A pearls are completely free of defects, while grade E pearls have many large holes or are completely cracked. In addition to being graded by quality, pearls are also classified by shape. There are three main categories of pearl shapes: round, oval, and teardrop. Round pearls are perfect spheres; they cannot be divided into two equal parts without cutting them apart. Oval pearls have two sides that are not exactly alike - one side is usually slightly rounded while the other has a sharper point.