Pearl Buying Guide

Pearls are the only gem that grows naturally in a living organism. Any mollusk with a shell -- oyster, clam, mussel, snail -- can produce a pearl, but pearls mostly grow in oysters. Pearls grow when a small irritant is caught in the oyster's tissue. The oyster covers the irritant with nacre, also called mother-of-pearl; thus, the small invader becomes the nucleus of a lustrous pearl. The layers of nacre keep accumulating as long as the pearl stays in the oyster.

Natural and cultured pearls

Mollusks are found in all oceans and many rivers and lakes, but freshwater and saltwater pearls that are good enough to be included in jewelry are so rare that, historically, they've been limited to the wealthy or the royal. Today, the farm grown or cultured pearl is affordable to almost anyone who wants a pearl necklace, ring, even a tiara.

Most modern pearl jewelry uses cultured pearls; they are genuine pearls, just made with a little help from humans. The process begins when a "nucleus" is implanted inside a pearl oyster, instead of waiting and hoping for it to happen naturally. Since mollusks simply can't keep up with the demand for pearls, growing cultured pearls is now a major industry. Natural oyster pearls are still available, most often in vintage estate jewelry.

Types of pearls

Akoya: This is the original cultured pearl, farmed in the coastal waters of Japan and China. They measure 2-10 mm in diameter, averaging 6-7 mm. These cultured pearls are consistently round, so a cultured pearl necklace is very likely made of Akoyas.

Freshwater: Farmed in lakes and rivers, most freshwater pearls on the market originate in China. The size range is 2-13 mm, averaging 6-7 mm. Freshwater pearls are white when harvested, but jewelry manufacturers dye the pearls in many colors. The dyed black pearls can have rainbow iridescence, a unique characteristic of freshwater pearls.

Keshi: When an oyster spits out the nucleus, it might still produce a pearl. Because it's an accidental by-product of the cultured process, it is still considered a cultured pearl, even though it's solid nacre. Keshi pearls come from saltwater or freshwater farms and, though formerly common, modern farming techniques have made keshis rare.

Mabe (pronounced MAH-BEE): Mabe pearls grow against the oyster shell. This "blister" pearl is hemispherical in shape. Once harvested, the nucleus is replaced by resin and the flat back covered in mother-of-pearl. Mabe pearls have very high luster and are less expensive than rounds.

South Sea: Cultured in the waters between Australia and China, these are among the largest cultured pearls, ranging from 10-20 mm, averaging about 13 mm. The colors for South Sea pearls are beautiful (and completely natural) white, cream and gold.

Tahitian: Actually cultured all over French Polynesia but traded from Tahiti, a Tahitian pearl is a naturally grey, silver or black pearl that measures 8-16 mm in diameter. The most sought after Tahitian pearl is black with peacock green overtones.

Pearl quality

The jewelry industry grades pearl quality using these factors:

Size: Pearls are measured in millimeters (mm); 25.4 millimeters equals 1 inch, so a 6-mm pearl is just under one-quarter-inch in diameter.

Color: The natural pearl colors feature various shades of white, gold and black, with creamy shades of white being the most common. Some special effects of color are overtone, a translucent color that lies over the main body color of the pearl and orient, iridescent colors in the pearl.

Shape: Spherical pearls are the most sought-after for elegant pearl bracelets and pearl necklaces. Pearls, however, come in many shapes, including drop, button, oval and seed pearls, baroque (asymmetrical) and coin (flat); all are great for decorative pearl rings, pearl earrings and other jewelry items. Shape depends on the oyster, its health, the temperature and chemistry of the water and other factors. Pearl farmers stack the odds by placing round nuclei into their oysters.

Luster: This is the way light travels through the pearl and reflects back to the eye. Because pearls are round, the layers act like mirrors, making pearls appear to glow from within. The luster grade depends on the sharpness of the reflected images.

Surface quality: Like diamonds, few pearls are perfect; blemishes on a pearl can be spots, pits or scratches. The highest-quality pearls have very few blemishes.

Nacre quality: This is the mother-of-pearl layers that form the pearl. The thicker and more even the layers of mother of pearl, the higher the quality.

Matching: This is important when considering a group of pearls for a pearl necklace, bracelet or jewelry set. Consistency in color and size of the pearls creates a more beautiful the appearance for jewelry and increases the value.

Pearl grading

Saltwater pearl grades

This grading system applies to all the akoya, South Sea and Tahitian pearls sold on Overstock.com. Please note that there are variances in the grades. For example, a pearl can have a shape other than round and still have an AAA grade.

AAA: Pearls have a high luster and graceful shape. They are precisely matched in size, color and overtone relevant to the piece. The pearls can have minute differences that are barely visible for most people.
AA: Pearls have a nice shape and a medium to high luster. These have good uniformity in size, color and overtone. Pearls can have slight blemishes on the surface that are noticed only when looking closely at the pearl.
A: Pearls have an even shape and a low to medium luster. These are nearly uniform in size, color and overtone. Pearls may have blemishes and/or wrinkles on the surface.
B: Pearls have uneven shapes and a low to poor luster. The size, color and overtone may vary within each strand. Pearls may have blemishes and wrinkles on the surface.

Freshwater pearl grades

AAA: Pearls have uniformly round shape and a high luster. These pearls are carefully matched in size, color and overtone when appropriate for a piece of jewelry. Pearls can have slight blemishes on the surface that are noticed only when looking closely.
AA: Pearls may have a potato shape and a medium luster. These are fairly uniform in size, color and overtone. Pearls may have some blemishes on the surface.
A: Pearls have irregularly formed potato shapes and a low to medium luster. These pearls can be noticeably inconsistent in size, color and overtone. These pearls may have noticeable blemishes and wrinkles on the surface.
B: Pearls have low to poor luster and great variance in shape, size, color and overtone. These pearls have obvious blemishes and wrinkles.

Costume pearls

There have always been people who want pearls but could never afford them. From the Roman Empire through Queen Elizabeth I, whose passion for pearls created the artificial pearls industry in England, to the 21st Century, ingenuity has supplied what nature could not. Manmade pearls are called faux, artificial, imitations, manufactured, created or simulated. Manmade pearls have no value as gems, even though modern technology gives these fakes a realistic appearance at vastly lower cost. All faux-pearl jewelry sold at Overstock.com is identified in the product description.

Caring for pearls

Keeping your pearl jewelry in pristine condition requires a few preventive measures. Pearls are vulnerable to damage by the chemicals in cosmetics and hair products, so put on pearl rings and other jewelry last when you are getting dressed. Wipe them with a slightly damp, lint-free cloth after every wearing. Wrap the pearls in a soft cloth (damp linen prevents dehydration) and place them in a box set aside just for pearls.

Occasionally clean pearls with water mixed with a few drops of a mild dish soap, but don't soak the jewelry. Wipe the pearl jewelry with a soft cloth dipped in the solution, rinse the cloth in fresh water and wipe the pearls again. Then dry the pearls. Avoid cleaning pearls in an ultrasonic jewelry cleaner as the process is too rough for the delicate gems.