Pearls are produced in a variety of colors, as noted in the types of pearls. Most range from white, cream, and yellow to pink, silver, and black. Most pearls will have both a primary color, the first color you will notice, and a secondary color, the overtone you notice when you take a closer look. Color variation does not decrease the value of the pearl, but is important when matching pearls to be used in strands, earrings, bracelets, etc.
A pearl's luster is the result of multiple layers, also called the nacre (NAY ker), that the oyster or mollusk secreted to make the pearl. The thicker the nacre, the more luster a pearl has. You will notice the luster as the deep sheen that reflects light on the surface of the pearl.
Pearls come in a variety of different shapes. The most coveted of these is round. Akoya, Tahitian, and South Sea pearls are most often the roundest of the pearls. Other shapes can make beautiful jewelry as well, sometimes providing you with different price options.
Because pearls rely on an uncontrollable environment in which to grow, very rarely will you find a perfect pearl. The surface of a pearl may not always be smooth, often including spots, bumps, etc. The beauty of these pearls may be enhanced by the ability to sometimes be camouflaged during the stringing and setting process.
The size of the oyster or mollusk that a pearl is produced within will have a direct effect on the size of the pearl. The size alone may not greatly impact the price of a pearl, but when you combine it with a perfectly round shape and beautiful luster, the value will dramatically increase.