Because of their beauty, rarity and difficulty harvesting, pearls have been called the "diamonds of the ocean." They are considered a gem, in the precious category. Pearls are amongst the oldest and most universal of all gems. They are the oldest jewels known to man, and the only gem made by a living animal. The oldest surviving pearl necklace is nearly 2000 years old, found in the sarcophagus of a Persian princess. There are many references to pearls in the Bible and its comparison to great value.

In any discussion about pearls, assume the pearls being discussed are cultured pearls, as natural pearls are extremely rare and expensive and not typically found for sale in the retail jewelry market.

Types of Pearls

If you are considering purchasing pearls, whether in a string or as an ornament in jewelry, become familiar with the different types of pearls.

Japanese Akoya Cultured Pearls: These are investment-grade saltwater pearls with a symmetric round shape and sharp reflection.

Chinese Akoya Cultured Pearls: These are saltwater pearls cultured in hybrid oysters. Their reflection is rather dull and they are not investment grade. They are typically used for jewelry in lower-end stores.

White South Sea Cultured Pearls, Black South Sea Cultured Pearls and Golden South Sea Cultured Pearls: Like the Japanese Akoya, these are also investment-grade saltwater pearls with symmetric round shape and sharp reflection. The difference in appearance refers to the color of the pearl, with white being a classic pearlescent white, the black being a luminescent black and the golden having a distinctive yellow gold hue.

Freshwater Cultured Pearls: These are not investment grade and are used to create jewelry for lower-end stores and boutiques. That's not to say they aren't beautiful - but they are not investment quality. They have a sharp reflection and irregular shapes that make them quite unique.

High Grade Freshwater Cultured Pearls: These freshwater cultured pearls are from China and although not investment grade, have a round shape and sharp reflection. They can be found in lower-end jewelry stores and departments.

Determining Quality

Luster: Luster is the amount of light reflected from the pearl's surface. Pearls with sharp reflection have more luster than pearls with dull reflection. Luster manifests in the surface glow so characteristic of pearls, as well as the mirror-like reflection of light. When buying pearls, you look first for this distinctive pearlecent luster.

Surface perfection: Tiny marks found on pearls are part of their natural texture and are proof of the genuineness of a cultured pearl. These blemishes are produced by outside sea particles and objects that find their way into the oyster and brush against the pearl. Although surface imperfections are expected - indeed, looked for - the more minimal the surface imperfections, the greater the value of the pearl.

Color: Pearls have a wide spectrum of colors, including cream, gray, green, blue and pink. The most popular colors are pink and rose, as they flatter the widest range of skin tones. Obviously, black pearls should have a deep, rich black color and golden pearls should have the luster of yellow gold.

Shape: Perfectly round pearls are the rarest and most valuable. Button pearls are round on one side and flat on the other. Other shapes, such as teardrop and baroque, are prized for their uniqueness. Freshwater pearls are irregularly shaped, so shape is not a factor in determining quality.

Size: The larger the size of the pearl, the higher the price. Large pearls are more difficult to cultivate. Pearls are measured in diameter increments of millimeters (mm).