What are Black Pearls?

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  • Written By: Jane Harmon
  • Edited By: Niki Foster
  • Last Modified Date: 17 December 2019
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A pearl is a hardened 'stone' formed inside certain types of oysters as a protection against grit that has entered their shells. Black pearls are not actually black, but very dark gray, with overtones such as blue, green or purple. For centuries, they were prized for their rarity; most pearls are white, cream-colored or a very pale shade such as pink. White pearls can be stained to appear to be naturally black by dipping them in a solution of silver nitrate. Experts can easily distinguish a phony black pearl from the real thing.

However, real black pearls are becoming increasingly common as cultured, or cultivated, pearls, and their price correspondingly has become much more affordable. Black pearls can vary widely in darkness of color, hue and iridescence. Iridescence is that quality which allows a stone to show different colors when light strikes from different angles.

Culturing pearls is a practice over a hundred years old. To 'grow' pearls, rather than harvest oysters and look for naturally occurring pearls, a tiny bit of grit is introduced into the shell of an oyster. Over two or three years, the oyster secretes a coating over the grit to prevent it from irritating the oyster's soft flesh. The coating is the same shade as the nacre or mother-of-pearl lining of the oyster's natural shell. One species of oyster native to the Polynesian islands, the Pinctada margaritifera or giant blacklipped oyster, will produce pearls of a dark color, or 'black' pearls, when cultured.


Black pearls are quite popular in modern jewelry-making. They are either matched in color and iridescence, or black pearls of different undertones and hues are strung together. Sets featuring perfectly matched pearls are much more costly, due to the difficulty in finding stones that are indistinguishable from one another.


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Post 3

@ Alchemy- Another reason to buy premium cultured pearls is because detection methods for natural pearls are falling behind methods used to create cultured pearls. I was reading an article in Nova (PBS) that talked about a new Chinese technique that used tiny off round natural pearls as the nuclei to create cultured pearls that receive gem lab reports branding them as expensive naturals. These pearls are all-nacre and can be sent to market as premium quality naturals.

Post 2

@ Alchemy- Freshwater pearls are different from saltwater pearls. If you are purchasing a black pearl necklace, you should probably go with a high quality cultured pearl necklace versus a natural pearl necklace because the cost will be very significant, and you will not be able to tell the difference without very expensive machinery.

To tell the difference between cultured and natural pearls you need to use a gemological x-ray. natural pearls have concentric rings that go all the way to the core of the pearl, while a cultured pearl is characterized by a starter bead, or a piece of mantle. Beaded and beadless cultured pearls will both have very different core x-rays from a natural pearl that

started forming mother of pearl rings around a microbial parasite or piece of organic matter.

If you need to tell the difference between an imitation pearl and a cultured or natural pearl, you can use the tooth test. If you rub a pearl against a tooth or another pearl, and it feels silky smooth, you have a fake. Real pearls have tiny bumps and divots.

Post 1

How can one tell the difference between black freshwater pearls and cultured black pearls? My wife likes pearls, and I thought a little necklace with black pearls would be nice for Valentine’s Day.

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