Mostly there are 3 types of pearls:
Natural Pearls are formed when some type of irritant, such as parasite (not proverbial grain of sand) works itself into an oyster, clam or mussel. As a mechanism of defense, a fluid is secreted and covers the irritant. This forms layer after layer of a coating, called ‘nacre’, and is deposited until a pearl is lustrously formed.
A cultured pearl goes through the same process. But there is a difference; the irritant is a surgically piece of bead or shell is implanted. It is known as Mother of Pearl. These pieces, nuclei or seeds are usually made from mussel shells. Now cultured pearls of quality need an adequate quantity of time which is usually over three years for a really thick coating of nacre to be set around, resulting in a pearl that is gem-quality and beautiful. Lower quality pearls have been taken out of the oyster too soon (often a year or less) so they have only a thin coat of nacre.
We are all aware of the fact that pearls signify royalty and magnificence. It is also a great gifting option to someone you are close to. Indeed they are expensive but they are worth the money you pay for. During the Roman era, pearls were regarded as a status symbol. They are not produced in the most ordinary of ways in fact they are produced by mollusks. However you need to understand that not every mollusk would be able to produce pearls. The mollusks which belong to the Conchifera class will only be able to cultivate pearls.
Saltwater vs. Freshwater
Pearls come from either freshwater or salt sources and historically saltwater pearls are rounder and have better nacre than pearls that are freshwater. Freshwater pearls has are inclined to be irregular in shape with an appearance that looks like puffed rice. But, improvements in freshwater pearl farming innovations have narrowed that gap with freshwater pearls currently exhibiting deeper luster and greater roundness.
The process of culturing normally takes several years. Mussels need to reach an age of maturity that often can take over 3 years and only then can be naturally or by implantation given an irritant. When that irritant is placed, it takes up to 3 more years for a pearl to get to its complete size and nacre thickness. These that produce pearls, about 5 percent, are going to be known as true gem quality for the top jewelry makers to use. A pearl farmer figures on spending over $100 for every oyster farmed.
For jewelry that is made from pearls, you will find an excellent collection at http://www.pearlsonly.co.uk/