Freshwater Pearls
Freshwater pearls come from freshwater mussels and are primarily produced by China. Freshwater pearls come in various pastel shades of white, black, pink, peach, lavender, plum, purple, and tangerine, depending on the type of mussel. The typical size of freshwater pearls is 2mm - 16mm with 7mm - 8mm being the most common.

Akoya Pearls
Akoya pearls are the classic white pearls and typically have the highest luster and greatest shine of all cultured pearls. Typical Akoya pearls range from 5 mm to 11 mm, with the 10 and 11 mm sizes rare finds. The most common size and the best value is between 7.0mm - 7.5mm with a sharp jump at anything 8.0mm and above. The Akoya pearl is either white or cream in body color and typically have a rose, cream or Ivory overtone; Akoya pearls may also be treated to achieve a black body color.

Tahitian Pearls
Tahitian Pearls come from the warm waters of the South Seas and are grown in a Black-Lipped oyster. They are the only pearl to achieve a black body color naturally and are typically very large(9mm - 16mm). Tahitian pearls although mostly dark can come in a wide range of hues, including black, gray, silver, green, blue and purple.

South Sea Pearls
South Sea pearls are saltwater pearls cultivated from the oyster, found in the South Seas centering on Northern Australia and South-East Asia including Myanmar and Indonesia. They produce 10-20 mm pearls of silver or gold color the largest of any cultured pearl. South Sea pearls are also the most expensive pearl on the market, due to thier rarity and thick nacre.

Each type has its own characteristics due to the specific forming condition. We normally classify pearls by origin, then grade them within the types they subjected to by luster, shape, surface quality, size, color, etc.

Luster

Pearls produce an intense, deep shine called luster. This effect is created when light reflects off the many layers of tiny calcium carbonate crystals that compose the pearl. This substance is called nacre. When selecting a pearl, consider that the larger the pearl, the more nacre it has, so it will also exhibit even more luster. Compare a 5mm Freshwater cultured pearl with a 10mm South Sea cultured pearl and the difference in the amount of nacre is obvious. The difference in luster is as clearly visible as the difference in the pearl sizes.

Shape

Shapes that are not spherical or even symmetrical are considered lower quality. Akoya, Tahitian, and South Sea pearls found in jewelry have a tendency to be the roundest, while Freshwater pearls can be oval or slightly off-round.

Surface
As a mollusk creates a pearl, the layers of nacre do not always adhere smoothly. Sometimes spots and bubbles can appear in the layering process. Pearls with the smoothest surfaces are the highest-quality, most sought-after pearls.

Size

Pearls are measured by their diameter in millimeters. Tiny seed pearls can be smaller than 1 mm, while South Sea pearls as large as 20 mm have been found. If all other quality factors are equal, the size of a pearl will determine its value. Only a 1 millimeter increase in pearl size is a substantial jump in both appearance and value. The importance of a pearl's size to its ultimate value depends on the pearl type.