Orient is the deep inner glow and shimmering irridescent characteristic of sea-grown pearls. The deeper the lustre and irridescence, the more precious the pearl. Size contributes to the price of a pearl. As it is more difficult for oysters to grow large pearls, they are scarcer. But two pearls of different sizes may be valued the same if the smaller pearl is superior in orient to the larger.
Shape determines value, too.
The more symmetrical the shape, the more valuable. Pearls of irregular and asymmetrical shape are termed baroque. Oysters grow pearls in many different shapes, from perfect spheres to long flat angel wing pearls. Surface perfection contributes to value. The surface of a perfect pearl appears satiny smooth.