Natural pearls are an extremely difficult kind to come by nowadays. You have to slaughter thousands of pearl oysters in order to find just one Good quality natural pearl. In the best pearl beds inside the Gulf of California -called "placer" in Spanish- the incidence of natural pearls was said to be in the range of 5 to 12%, meaning that for every 100 killed oysters you would only find some 5 to 12 pearls.
Yet, you would have to take another factor into consideration: of those pearls, only 30% would be of good quality. So, out of those possible 12 pearls, only 3.6 good pearls (large and beautiful enough) could be obtained. This intensive fishing effort had its adverse results on the viability of the natural pearl oyster populations throughout the World, most becoming exhausted beyond help.
Natural pearls are formed when the pearl oyster forms something called a pearl sac. This pearl sac is the result of external stimuli (a parasite -mostly polychaete worms- or even other form of mechanical damage) on the nacre (commonly called mother-of-pearl) producing cells of the oyster's mantle. This pearl sac engulfs the foreign body, and starts depositing thousands of very thin layers of nacre over it, encapsulating it to protect the oyster. After some years (2 or more), a Natural pearl of good size (4-12 mm) can be found inside an oyster.
In essence, a Natural pearl is identical to an onion in its inner structure: both are made of overlapping layers.
Natural pearls are -usually- worth around 10 times more than their cultured pearl equivalent.
Cultured pearls are formed by the joint efforts of Man and Mollusk, as opposed to a natural pearl. A cultured pearl is made of the same substance and formed in a manner similar to a natural pearl, but inside a cultured pearl you will have a mother-of-pearl bead, not a parasite. Cultured pearls are produced inside farm-reared pearl oysters (if done in a Sustainable manner).
Note: A cultured pearl must not be confused with a fake or artificial pearl (like "Mallorca" or "Majorica" pearls). Imitation pearls are not real pearls but man-made products.
To grow a cultured pearl, you require a Pearl Oyster or Pearly Mussel. These animals are induced to produce a pearl -taking advantage of their own natural pearl production schemes- so this results in an man induced pearl, with all the traits of the natural one, except for its "core" and the fact that it was not spontaneously produced by a natural ocurrence.
This procedure to induce the production of a cultured pearl is called pearl grafting (but also known as the "pearl seeding operation") and its scientific basis (the "Pearl Sac Theory") was discovered at the beginning of the 20th Century by Australian researcher William Saville Kent, and his discovery was later put to work in a commercial manner by Japanese Pearl Farming Pioneer and Father of the Cultured Pearl: Kokichi Mikimoto.
So, the main difference between a cultured pearl and a natural pearl is its core, center or "heart": the presence or absence of a mother-of-pearl nucleus. Cultured pearls will have one one of these special beads inside, whereas natural pearls will have a bit of organic matter instead.
The "Problematic Pearls" - Beadless Cultured Pearls
But there are another group of cultured pearls that are more problematic: they cannot be as easily differentiated. They are commonly refered to as non-bead nucleated (or beadless cultured pearls) pearls, such as:
- Keshi Pearls
- Ikecho (or Fireball) Pearls
- Edison (or Souffle) Pearls
We will not go into details as to how these pearls are co-created, but they do not possess a bead or nucleus inside them, yet they are very different from natural pearls due to their more "hollow" interior.