Some people use the term "black pearl" to refer to any dark colored pearl, dyed or natural color. Black pearls are not necessarily black. More often than not they range from a light to very dark gray, but they may also look green, pink, lavender, blue or brown. It's the oyster source, not color, that determines if pearls are called

black pearls. "Black pearl" is a generic term that refers to pearls from:

• Black-lipped pearl oysters (Pinctada margaritifera), Western to Central Pacific & Indian Oceans.

• La Paz pearl oysters (Pinctada mazatlanica), Eastern Pacific between Baja California & Peru.

• Rainbow-lipped (western-winged) pearl oysters (Pteria sterna), Eastern Pacific between Baja California & Peru.

Some people mistakenly identify all black pearls as Tahitian pearls. Tahitian pearls are found in French Polynesia and they're marketed in Tahiti. Pearls from the Cook Islands are Cook Island pearls, not Tahitian pearls. Black pearls from the Gulf of California can be called La Paz pearls, Mexican pearls, Baja California pearls or simply black pearls. Some sellers call black pearls from the rainbow-lipped oyster "rainbow pearls" because of their natural rainbow-like colors.

If you go to Hong Kong, you may see strands labeled "black pearls" that sell for a couple hundred dollars. They are probably artificially colored Akoya pearls whose natural color was undesirable. In Tahiti, "black pearls" must be of natural color to merit the name of "black pearl" or "Tahitian pearl." The jewelers in both areas are correct in their use of the term "black pearl" as long as the treated pearls are identified as dyed, irradiated or treated black pearls. In other words, the unmodified term "black pearl" implies the pearl is of natural color.

Over 99.9% of the black pearls sold on the market today are cultured. So for the sake of brevity, this book often leaves out the term "cultured" when referring to cultured black pearls. Nowadays, when pearls are natural, they are identified as such. A few natural black pearls have been recently found in the Pteria sterna oyster off of Baja California. Natural pearls (those created without human intervention) are rare, so don't expect to find them in your local jewelry store.

Natural-color black pearls can be confused with natural-color "blue pearls. " Unlike black pearls, whose color is an inherent characteristic of the pearl nacre, blue pearls derive their color from foreign contaminants in the nacre itself or between the nacre and the shell bead nucleus. Naturally colored dark Akoya pearls are good examples of blue pearls. They may be blue, black, gray or brown. Black pearls and blue pearls can look the same but because of the difference in the origin of their color, blue pearls are worth less. The fact that blue pearls might decay or lose their color if holes are drilled through them is another reason for their lower value.

Since there can be a great value difference between black pearls, blue pearls and artificially colored pearls even though they may look the same, consumers need to be concerned about buying black pearls that are misrepresented. In Chapter 12, you'll see how to spot pearls that are not true black pearls. Keep in mind, though, that the only sure way to identify a natural-color black pearl is to send it to a lab and have it tested.