Real or Fake Cultured Pearls
Real pearls are grown within mussel or a like kind of living mollusks and oysters.
Imitation pearls or "false pearls" are made of glass, plastic, or shell beads dipped and coated with ground fish scales. Imitations come in a variety of types. The main ones are:
Hollow glass beads containing wax - likely made by the same process as Jacquin's in antique jewelry.
Solid glass beads - Majorica imitation, for example, is covered with as many as forty coats of pearl essence mixed with other substances and hand polished between each coat.
Plastic beads - sometimes hang poorly due to their light weight.
Mother-of-pearl shell beads - shell or clay beads coated with substances such as plastic and glass and then baked.
Sometimes customers interested in buying pearls are concerned that they won't know the real thing from the imitation. Here are some tests to help you determine if you are looking at well-done 'fakes' or genuine pearls.
An old wives' tale says that if you hold real pearls in your hand, they will be cool to the touch for several seconds before warming up. Genuine pearls tend to warm with contact to the skin much faster than glass pearls. Resin or plastic pearls tend to feel somewhat warm upon first contact. This however is not a sure-fire method for checking authenticity.
The Tooth Test
Rub the pearls lightly along the biting edge of your upper front teeth. If they feel slightly rough, sandy or gritty, it's likely they are cultured or natural pearls because of the layers of nacre that have formed over time. If they feel smooth or glassy, they are probably imitations. That's because the imitations are made by dipping a plastic or glass bead into some sort of paint, sometimes including iridescent fish scales. You will also get the same result (rough, sandy, or gritty) if two pearls are rubbing together.
This test doesn't always work. It is not the most sanitary test. It may scratch the pearls if done improperly. Therefore, don't rely solely on the tooth test. If you use it, combine it with the magnification tests listed below.
Examine the surface of the pearl with a 10-power magnifier such as a loupe. If it looks grainy, there's a good chance it is an imitation. Pearls normally look unusually fine-grained.
Fakes tend to look 'flat' in comparison to the real thing. Characteristics of fakes are the grainy smoothness of surface, 'perfect round' (although expensive genuine pearls may be round) shapes and 'uniform' dull luster.
Real pearls tend not to be perfect and may have bands in their nacre, bumps, ridges, pits, even flaws or blemishes on surface. They vary in size and shape from one to another. They bear rich overtone except their body color. These sorts of imperfections and irregularities characterize genuine pearls.
A surface with tiny, crooked lines giving it a scaly, maze-like appearance is characteristic of cultured and natural pearls. Try using a strong, pure, direct light such as a fiber-optic and shine it on the pearl from various angles to find the scaly lines.
The best way to learn what the surface of pearls and imitations look like under magnification is to examine many examples of each. When you can differentiate their surface textures, you won't need to do any of the other tests to spot an imitation pearl.
Drill Hole Test
Examine the drill hole area with a magnifier of 10-power or above. (On some pearls, it may be hard to see into their drill hole.) Cultured pearls tend to show the following characteristics:
There is often a clear dividing line between the nacre and nucleus.
The edges of the drill holes are often sharp and well-defined. But when the nacre wears away it can leave the holes looking jagged and rough.
The drill holes tend to be like a straight cylinder.
The pearl nacre coating is normally thicker than the coating of imitations.
Imitation pearls tend to show these characteristics:
There is normally no dark dividing line between the coating and the rest of the pearl. Occasionally, one may see a kind of line, but the other characteristics of the drill hole will look like those of imitations. If you are in doubt, look at the drill hole opening on the other side of the pearl and on other pearls of the strand.
The coating around the edges of the drill holes may have flaked off, making it look ragged or uneven.
The drill holes may be angled outward at the surface of the pearl.
Other times the drill holes may round inward at the surface and bow outward inside the pearl.
The coating often looks like a thin coat of shiny paint. The thinness can be seen at the edge of the drill hole or around bare areas which expose the inner bead. Rounded ridges may have formed around the drill hole.
If you are looking at a strand of pearls at an antique store or estate sale, look carefully at the drill holes. The coating over imitation pearls will fade, chip or even discolor over time. You can easily see chips or flakes around drill holes. Examining the hole is also a good way to detect signs of dyeing.
The best way to guarantee that you are buying real pearls is to always deal with a reputable pearl dealer.
Real pearls tend to be drilled from both sides, to meet in the center. If you could see the cross section of the pearl, the hole may appear wider at the outside edge of the pearl than at the center (which can make stringing poorly-drilled pearls very challenging). One reason for this is because a bigger hole means less weight and lower value, since the weight of a pearl affects its price.
The holes of fake pearls often form a shallow bowl shape while the holes of real pearls are more likely to be flat.