Black Pearls
Pearls are usually thought of as being creamy-white in appearance, however they also come in a variety of other colours, including black (or at least near-black).
Natural vs Cultivated
Natural black pearls are very rare and have great value - the black-lipped pearl oyster Pinctada Margaritifera rarely produces pearls at all under normal conditions. If we ignore pearls that have simply been dyed, the majority of black pearls you can buy in jewelry today are cultivated. This is actually true for all pears, black or otherwise; natural pearls created spontaneously with no human intervention are too expensive for most of us to buy.Cultivation is the norm with pearls you can buy today, even more so for the black variety. Cultured pearls are still natural in the sense of being formed by a living sea creature, however the natural pearl formation has been "bootstrapped" artificially.
Black pearls can be very striking and are used today in all forms of jewelry including necklaces, earrings, pendants and rings. Even though the cultivated black pearl is more affordable to buy today than the natural variety of old it still carries an almost mystical aura of wealth and exotic treasure.
Tahitian Black Pearls
The main source of cultivated black pearls is the Polynesian lagoons of the South Pacific islands, in particular Tahiti. The name "black pearl" is sometimes used to refer to any pearl formed by Pinctada Margaritifera, regardless of colour, however in common use most people expect a Tahitian Black Pearl to be black or at least a very dark shade.Although cultivated South Sea pearls have been sold since 1917, the commercial cultivation of the Tahitian black pearl began relatively recently in the 1960s.
Symbolism
As a rare and difficult to find object the black pearl is frequently used as the treasure at the end of a quest - whether it's an actual pearl or whether it's a metaphor for something less substantial.These romantic dark stones are frequently associated with pirates, especially since the movie Pirates of the Caribbean: Curse of the Black Pearl. For the metaphorically minded the black pearl might have represented his black heart, this being one of many meanings they're sometimes given.
Black pearls are also associated with Sherlock Holmes, through the story The Six Napoleons where Holmes locates "the famous black pearl of the Borgias".