Essentially, there are 3 kinds of pearls: imitation, cultured, and natural.
Natural Pearls will form as an irritant – typically a parasite; not a grain of sand – will work its way inside a clam, mussel, or oyster. A fluid, as a defense mechanism, is utilized to coat this irritant. Layer after layer of the coating referred to as ‘nacre’, will be deposited until a pearl is formed.
Cultured pearls undergo the exact same process. The difference is that an irritant includes a surgically implanted bead or shell piece named Mother of Pearl. These ‘nuclei’ or ‘seeds’ most often are formed from a mussel shell. Cultured pearls of high quality will require a substantial quantity of time – usually at least three years – for nacre to be deposited, and result in a gem-quality, beautiful pearls. Low quality pearls often have been ‘rushed’ out of an oyster too fast (1 year or less) and possess an overly thin nacre coat.
Usually, the culturing process will take several years. A mussel has to get to a mature age– that may take up to three years; only then may it be implanted or receive an irritant naturally. As an irritant is in place, it may take up to an additional three years for a pearl to get to its full nacre thickness and size. Of the produced pearls, only around 5 percent are of substantial real gem-quality for leading jewelry makers, but a pearl farmer may figure on spending more than $100 for each oyster which is farmed, whether or not a gem-quality pearl is produced.
An imitation pearl is a whole different story. In many instances, a glass bead will be dipped inside a solution that is made of fish scales. The coating is thin and might ultimately wear off. Usually, one may tell if the piece is an imitation by rubbing it across his/her teeth: Fake pearls will glide across the teeth, whereas the nacre layers on real pearls will feel gritty. Island of Mallorca is well-known for its industry of imitation pearls, and the words “Majorica Pearls” or “Mallorca Pearls” frequently is used to define these pearl simulants.