Why are Black Pearls Black?

types of black pearls
From left to right: Black Tahitian Pearls, Black Akoya Pearls and Black Freshwater Pearls

Pearl lovers with a taste for the exotic often gravitate toward the undeniably enchanting black pearl, a mysterious gem if ever there was! Of course, “black pearls” aren't actually black but instead the term is used to describe pearls that have a dark body color, usually green, blue purple or gray. Commercially speaking, there are three types of cultured black pearls on the market; black Akoya pearls, black Freshwater pearls and black Tahitian pearls. Black Tahitian pearls are the only type that occurs naturally. Tahitian black pearls are born with their mysteriously gorgeous body colors and unique coloration that makes them prized as rare treasures around the world. Black Freshwater pearls and black Akoya pearls are also available, but they are dyed or irradiated, a permanent but artificial process.

Black Tahitian Pearls

This organic gem of the sea hails from the black lip oyster, known scientifically as Pinctada margaritifera-cumingi. The oysters make their home in the waters of French Polynesia, taking their name from the island of Tahiti, although no pearls are farmed around the island of Tahiti. While large Tahitian pearls are relatively rare when compared to Akoya or Freshwater pearls and typically much larger. Some Tahitian pearls have been grown as large as 20 mm, however most fall within the 9-15 mm range.

Tahitian Pearl Color

black tahitian pearl colors
The exotic colors of the Black Tahitian Pearl

When culturing a Tahitian pearl, technicians insert a small square of donor mantle tissue with a mother of pearl shell bead. Mantle tissue will influence the pearl's color; depending on colors present in the shell of the donor mollusk. It may lead to shades of plum, green, blue, or gray depending on the tissue used. As well as body color black Tahitian pearls often exhibit strong overtones of green, red, aubergine or peacock. The end result is a pearl that boasts a dark body color and overtones that are only present in black Tahitian pearls.

Black Akoya and Black Freshwater Pearls

Jewelry technicians employ dyes or irradiation to transform light colored pearls into black pearls. One treatment involves an akoya or freshwater pearl that is dipped or soaked in a silver nitrate solution which darkens the pearl's nacre like a dye. Irradiation is also used; this process employs gamma rays that darken the nucleus of the pearl. While these processes are artificial they are considered permanent and often produce fantastic body colors many find appealing.

Is It Possible to Spot the Difference between Treated and Tahitian Pearls?

Yes, but it isn't always easy! Treated pearls tend to be far more uniform in color than Tahitian pearls which typically show some natural variation. Sometimes looking within the drill hole of a pearl will allow the viewer to see a darkened nucleus or signs of dye. Most black Tahitian pearls will be untreated and all black Akoya and Freshwater pearls will have some sort of treatment for color. Watch out for ebay sellers selling dyed Freshwater pearls as Tahitian pearls, this is a very common scam.

Reputable jewelers will disclose whether the pearl is a Tahitian or dyed Akoya or Freshwater pearl, but it's always best to do your own research to better understand exactly what it is you're purchasing.

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