Pearls, natural and cultured, occur in a wide variety of colors, with white and cream being the most familiar.
Natural pearls form around a microscopic irritant in the bodies of certain mollusks. Natural pearls can be separated from cultured pearls by taking X-rays to reveal their inner structures.
- Cultured pearls are the result of the deliberate insertion of a bead or piece of tissue that the mollusk coats with nacre. The growth of cultured pearls requires human intervention and care.
- Imitation pearls are smooth when rubbed against your teeth, while natural or cultured pearls have a slightly rough texture.
There are four major types of cultured whole pearls:
- Akoya: Japan and China produce saltwater Akoya cultured pearls.
- South Sea: Australia, Indonesia, and the Philippines are leading sources of these saltwater cultured pearls.
- Tahitian: French Polynesia (the most familiar of these is Tahiti) is the most common source of these saltwater cultured pearls which usually range from white to black.
- Freshwater: China and the US freshwater lakes and ponds are the leading sources for these. They’re produced in a wide range of sizes, shapes, and colors.
The qualities that determine the overall value of a natural or cultured pearl or a piece of pearl jewelry are size, shape, color, luster, surface quality, nacre quality, and matching.
Size: Cultured pearls range from 2-16mm in diameter, depending on the mollusk used.
When other value factors are equal, larger pearls are more rare and valuable than smaller pearls of the same type.
Shape: Spherical pearls are the most valued but symmetrical drops are also sought.
Round is the most difficult shape to culture, making it the rarest cultured pearl shape and—if all other factors are equal—also generally the most valuable.
Color: Although white is most classic, appreciation has grown for more unusual natural colors.
Natural and cultured pearls occur in a broad range of hues. There are warm hues like yellow, orange, and pink, and cool hues like blue, green, and violet. Pearls have a wide range of tone from light to dark. Pearl colors tend to be muted, with a soft, subtle quality.
The law of supply and demand determines the value of certain pearl colors at any given time; other complex factors, like fashion trends and cultural traditions, can influence color preferences.
Luster: Luster results from reflection of light rays off the pearl’s surface, and from concentric inner layers of nacre, like light bouncing off a convex mirror. Pearls with high luster have sharp bright reflections on the surface.
Of the seven pearl value factors, luster might be the most important; within a pearl type, when other value factors are equal, the higher the luster, the more valuable the pearl.
Luster is what gives a natural or cultured pearl its unique beauty.
- Excellent – Reflections appear bright and sharp
- Very Good – Reflections appear bright and near sharp
- Good – Reflections are bright but not sharp, and slightly hazy around the edges
- Fair – Reflections are weak and blurred
- Poor – Reflections are dim and diffused
Surface quality: The number of blemishes on a pearl’s surface is evaluated to judge quality.
Like colored stones, most pearls never achieve perfection. Some may show abrasions that look like a series of scratches on the surface, or a flattened section that doesn’t affect its basic shape, or an irregular ridge that looks like a crease or wrinkle. If surface characteristics are numerous or severe, they can affect the durability of the pearl and severely depress its value.
Nacre quality: Nacre thickness is evaluated to make sure that cultured pearls are durable as well as beautiful.
Luster and nacre quality are closely related. If the nucleus is visible under the nacre, or if the pearl has a dull, chalky appearance, you can assume that the nacre is thin. This affects the luster as well as the durability of the pearl.
For pearl strands and multi-pearl pieces, how well the pearls match affects the value.
Jewelry designers sometimes deliberately mix colors, shapes, and sizes for unique effects, but for most pearl strands and multiple-pearl jewelry, the pearls should match in all the quality factors.
(Pearl Gemstone / Pearl Stone / Pearl Gem / GIA)