Different Types Of Pearls
The hunt for natural pearls dates back thousands of years to places like China and the Persian Gulf where divers would swim down to the ocean floor or river bottom to hunt for pearls. Diving for natural pearls was the only means of findings pearls until the late 19th and early 20th centuries where Japanese researchers Mise and Nishikawa developed a technique for creating cultured pearls. Both natural and cultured pearls come from Bivalves which are a family of living shelled molluscs of which there are about 20 pearl producing varieties. Of these only a few are used to produce the varying colour pearls we use today:
- Pinctada Margaritifera – Black-Lipped mollusks produce black Tahitian pearls (South Pacific).
- Pinctada Maxima – Gold-Lipped or Silver lip mollusks produce champagne or cream pearls (South Sea Pearls).
- Pinctada Maxima – White-Lipped mollusks produce silver-white, prink or cream tinged pearls (South Sea Pearls).
- Pinctada Fucata – Akoya pearls produce light pink, white or creamy pearls.
- Strombus gigas Linnaeus – Pearls from the Queen Conch are very rare and come in shades of cream, gold, grey, brown, orange, red, pink and white pearls.
These molluscs aside from the Conch are made up of two shell halves that open and close for feeding and depending on the variety can be found in salt water or fresh water. Most people think that oysters are the only shellfish that produce pearls, this isn’t the case as both mussels and clams also have the same capability although it much rarer for it to happen.
How Natural Pearls Are Formed
Oysters have a hard protective exterior shell wall but soft delicate bodies on the inside that need protecting. They live in sandy environments and when they get dirt and bits of sand inside their shell they just spit them out. So when you hear that pearls come from a grain of sand this isn’t strictly true. Parasites will sometimes burrow through the oysters outer shell wall and get trapped or die, other times small bits of shell, fish scales or other foreign bodies get caught on the inside shell wall and are unable to be dislodged. To protect its soft body the oyster forms a blister around the irritant that completely encapsulates the foreign body to form a sac. The pearl sack or epithelial cells as it’s also called secretes nacre and conchiolin which coats the irritant to form a pearl. Nacre is made up of crystallized calcium carbonate that is mother of pearl. This smooth thin coating is attached to the irritant by the conchiolin, which is a dark coloured natural organic protein which acts like an adhesive and is only produced to bond the first layer of nacre to the irritant. Throughout the pearls life the sac continuously expands to form concentric micro-layers of nacre around the irritant which gradually increases the size of the pearl in a process that takes years.
How Cultured Pearls Are Formed
Cultured pearls grow in pearl farms some of which are salt water and others freshwater. Unlike natural pearls where the process of an oyster creating a pearl occurs accidentally cultured pearl development is controlled. A nucleus is inserted into the soft tissue of the mollusc, in the case of freshwater pearls a piece of mantle tissue is used and for salt water pearls a mother-of-pearl nucleus is used. The nucleus is usually round in shape as pearls tend to develop into the same shape as the inserted nucleus which acts as a mould. The artificially inserted nucleus which is basically a round bead is nearly as large as a natural pearl; this is because cultured pearls only have a thin layer of nacre, while natural pearls are mostly made of nacre. Once the nucleus is inserted into the oyster the pearl growing process is the same as that of a natural pearl.
Natural vs Cultured Pearls
The process of culturing pearls revolutionised the pearl industry and meant that pearl farmers could control the cultivation of large numbers of consistently high quality pearls. This allows farmers to produce millions of pearls at a time there bye reducing their market value to a level that is affordable to everyone. Natural pearls have become extremely rare because of the huge volumes that were hunted for in the 1800s, which left the world’s natural supply critically low. Add to that the fact that only one in approximately every 10,000 oysters will produce a pearl and of these only a small amount will be of sufficiently high quality. It can take an oyster 5 years to form a tiny 3mm pearl in the wild where as a 7mm cultured pearl can be created from a 6.5mm nucleus in just 3-5 years.
Consistency is another big benefit of cultured pearls, where it’s extremely rare and difficult to find a string of natural pearls that are the exact same shape, colour and size. If one did exist it would be worth hundreds of thousands of pounds where as the same string of cultured pearls would cost just a few hundred pounds. The most desirable shape for pearls is perfectly round which is easily achievable in cultured pearls but finding one is pot luck in natural pearls.
How Can You Tell The Difference Between Natural And Cultured Pearls?
It’s pretty much impossible to tell the difference between a natural and cultured pearl by just looking at its outer appearance. The only way to make absolute certain whether a pearl is natural or not is to perform an x-ray of the internal structure of the pearl. A natural pearl may show growth lines where concentric layers of nacre have been added. Cultured pearls on the other hand will appear to have a perfectly rounded nucleus that’s surrounded by a halo of conchiolin and finally a thin outer layer. Almost all pearls sold today for jewellery making are cultured pearls and just like natural pearls they come in varying colours, shapes and grades of quality. So when it comes to purchasing pearls you can be sure that they will be of the cultured variety which means that they are real pearls made by oysters and are not artificial as many people think.
Author: Crystal and Glass Beads