1SizeAll else being equal, a larger pearl is rarer. The longer it grows, however, the more likely surface marks become.
The pearl
Seven things to look for in a pearl
A pearl is assessed on seven factors. None is enough on its own: together they tell how beautiful a pearl is and what it is worth.
2ShapeRound is the hardest shape to culture and therefore the rarest; but well-formed drops, ovals and baroque pearls are also highly prized.
3ColorIt is read in three layers: the bodycolor, the overtone, a translucent veil lying over it, and the orient, a soft iridescent play on the surface.
4LusterPerhaps the most important factor: sharp, bright reflections indicate a quality pearl, dull and blurred ones the opposite.
5SurfaceA few slight marks, perhaps hidden by the drill hole or the setting, matter little; if they are many or deep they reduce beauty, durability and value.
6NacreThe substance the pearl is made of: luster and durability depend on its quality. A visible nucleus or a chalky look indicate a thin layer.
7MatchingIn strands and earrings, what matters is how closely the pearls match in size, shape, color, luster and surface. Intentional designs, such as multicolor or graduated strands, are the exception.