Cultivation
Pearls are produced naturally in the body of saltwater and freshwater mollusks such as oysters and mussels. When these animals sense an irritant, such as a grain of sand, they produce a soft coating of calcium carbonate substance around it. The result is a pearl. Because perfectly round, naturally produced pearls are so rare, a process known as cultivation was developed by Kokichi Mikimoto in the early 1900s. A small bead of polished shell, the nucleus, is used as an irritant. The nucleus is delicately inserted into the mantle of the mollusk. It takes approximately 20 to 24 months of intensive husbandry to cultivate a saltwater pearl and somewhat less time to cultivate freshwater pearls. The harvest usually takes place during the months of June and September.

Color
Image of Pearl Color 

Mollusks produce pearls in a variety of colors, accommodating most personal preferences and budgets. The general color of a pearl is also known as the body color. Pearls typically range from white, cream, and yellow to pink, silver, or black. An overtone of secondary color is sometimes seen. For instance, a pearl may appear to be white, but upon closer inspection a rosy hue is detected. The body color would then be termed white-rosé. Color variation does not affect the quality of the pearl, though it should be noted that color matching is important when choosing pearls for some necklaces, earrings, or bracelets. In fashion jewelry, pearls can sometimes be dyed to achieve the desired color, which should be mentioned in the product description or specifications.

Luster
Image of Pearl Luster 

The appealing, deep shine of a pearl is often what defines its beauty. This is produced by multiple layers of semi-opaque calcium carbonate crystals, called nacre. The nacre reflects light on the surface of the pearl, producing brilliance and sheen. Luster is an integral feature in determining the quality of a pearl. Large pearls have a thicker nacre and, therefore, a higher luster. When comparing a small freshwater pearl to a large South Sea pearl, the difference is clearly visible to the untrained eye and should be considered when purchasing pearls.

Shape
Image of Pearl Shape 

While pearls come in many different shapes, the rarest and highest-quality are round. Akoya, Tahitian, and South Sea oysters tend to produce the roundest pearls, while those of freshwater mollusks can be oval to slightly off-round. When considering a pearl purchase, the shape of each pearl should be consistent in a necklace, bracelet, or earrings. Many of the less symmetrical shapes can be quite beautiful and are used in stylish jewelry: the drop pearl's shape lends itself well to earrings, and the baroque pearl features irregular shapes that work well as necklace accents. In addition, a half sphere pearl called a mabe is often used in earrings, necklaces, and bracelets.

Size
Illustration of Pearl Size 

An oyster's particular type and size has a direct effect on how large the pearl it produces will be, and pearls do come in a wide range of sizes. Round pearls are measured according to their diameter, while baroque pearls are measured by their length and width. A pearl's size does not necessarily affect its quality, but it does affect its price. Large, round pearls are rare and their luster is usually high. This beautiful combination of traits is often reflected in the cost of such pearls. Average pearl sizes (in diameter): Akoya: 6-8mm, freshwater: 5-6.5mm, South Sea: 11-13mm, Tahitian: 11-12mm.

Surface Markings and Blemishes
Image of Surface Markings and Blemishes 

Often when an oyster creates a pearl, the nacre does not develop smoothly. The surface of a pearl is judged by how many marks are visible in the nacre. These imperfections can be small and unnoticeable or quite large and distinct. Like diamonds, pearls are rarely flawless. However, high luster or the way pearls are strung and set can help conceal surface markings.

Akoya Cultured Pearls
 Akoya pearls are produced in several varieties of saltwater mollusks in Japan and China. They were the first to be cultured, in the early 1920s, and are the most popular pearls used in strands and earrings. They produce the most consistently round pearls with high luster and very slight imperfections. Their colors range from cream and white to white-rosé. Initially, they look similar to round freshwater pearls, but compared side-by-side, the difference in luster and color is obvious.

Freshwater Cultured Pearls
 These pearls are gathered from freshwater lake and river mollusks. Most freshwater pearls come from China. They are mostly round to off-round, or rice-shaped to baroque. They appear similar to Akoya pearls but are the perfect gift when shopping on a budget. They might be slightly less symmetrical, smaller, or not as easily matched, but these minor differences provide a major value for the price.

South Sea Cultured Pearls
 South Sea pearls are primarily cultured in the northern waters of Australia, the Philippines, and Indonesia. They are either white or black with silver overtones. Because of their size, high luster, and sensitivity of the oyster to culturing, they are quite valuable and rare. They average from 11 to 13 millimeters but can even be found as large as 20 millimeters. The oyster that produces these pearls is considerably larger than those that produce Akoya pearls and is extremely sensitive to the cultivation process. Gathering acceptable South Sea cultured pearls from these oysters is difficult and makes them more expensive than Akoyas.

Tahitian Cultured Pearls
 The natural black color of the Tahitian pearl comes from the black-lipped variety of the Pinctada maxima oyster. These oysters are farmed on the volcanic atolls of Tahiti, where the mixture of nutrient-rich ocean water mixes with warm lagoons, creating an ideal environment for them--and the only place where Tahitian pearls can be found. Like the South Sea pearl oyster, the black-lipped Pinctada maxima is sensitive to the cultivation process, making the Tahitian pearl rare and expensive. Though they are, on average, slightly smaller than the South Sea pearl, Tahitian pearls are larger than Akoyas, and their black color adds a dramatic touch.

Pearl Care
Taking proper care of your pearls is not difficult if you remember that they are organic--produced by a living thing. Pearls are soft and delicate, but if cared for with common sense, they will maintain their luster for centuries. Pearls should not come in contact with cosmetics, hairspray, perfume, chlorinated water, or other harsh chemicals. To keep them clean, they should be the last item put on when dressing and the first item removed at the end of an evening. The best way to maintain their luster is to wear the pearls often and wipe them down with a soft cloth afterward--pearls absorb the oils from skin, which helps keep them moist. To avoid nicks or chipping, separate pearls from other jewelry by storing them in a cloth pouch or jewelry bag. Pearl strands should be restrung periodically because the silk thread used to tie the pearls together breaks down over time.