Pearls occur naturally when certain mollusks are infected with parasitic organisms or other such irritants, usually when they burrow through the shell into the tissue underneath. The mollusk’s immune system triggers the secretion of a mucus like substance called nacre, which coats the irritant to protect the mollusk from damage. Over time, the layers of nacre coating build up, resulting in the formation of a pearl within the shell. Pearls tend to retain the shape of the original irritant, and so most natural pearls are not round.
Naturally occurring pearls are rare, and many thousands of mollusks can be killed in the search for one pearl. This is why natural pearlsmand the highest prices, as the yield is unpredictable. As pearls are so desirable and so rare, pearl farmers have worked out ways to stimulate the pearl formation process, greatly increasing the yield of pearls. Originating in Japan in the early 20th century, pearl farming involves the artificial introduction of an irritant to the pearl yielding mollusk, followed by its return to its aquatic habitat. The pearls are then given between 2 and 6 years to grow, depending on the size of pearl required, before harvest. Each mollusk can produce up to 32 pearls.
Types of cultured pearls
Freshwater pearls are cultured in a freshwater environment, as the name suggests. Grown in lakes, ponds and rivers, freshwater mollusks are nucleated by inserting a small piece of mantle tissue into a young mollusk’s valve. This can be done up to 25 times per valve, although it is usual to limit insertions to 12-16 per valve. After the growth period the pearls are harvested,Replica Alain-Silberstein Watches, dyed (if required), drilled and strung for sale. Freshwater pearls are generally low quality, irregularly shaped and with a lesser luster than their saltwater cousins. As such, they fetch a much lower price, and so are in demand for costume jewelery.
Saltwater pearls are grown in marine mollusks, and are usually rounder and of a higher quality than freshwater pearls. This is because marine mollusks are nucleated with a small bead nucleus as well as the piece of mantle tissue which forms the bead sac, and having a round nucleus to form the scaffolding for the pearl reults in a round pearl being grown. There are multiple types of saltwater pearls available, which explains the confusion around what the various names for pearls actually mean.
Akoya pearls are grown in the akoya oyster, which s the smallest of the saltwater pearl oysters. As a result, akoya pearls are some of the smallest saltwater pearls available, and are rarely seen at more than 8mm. Akoya pearls were traditionally farmed in China and Japan, although these days most Japanese Akoya pearls are actually imported from China. Akoya pearls have a deep rich luster, and are generally round or near round, and either white or cream with rose pink overtones. They are extremely desirable for matching with existing jewelery due to their consistency of shape, colour and quality, and canmand fairly high prices.
Tahitian pearls are formed in the black lipped oyster in and around the French Polynesian Islands. The black lipped oyster is one of the largest pearls producing mollusks, and so the size of the resulting Tahitian pearls is larger than Akoya Pearls. Tahitian pearls are much darker than other saltwater pearls, and naturally occur in a range of colours, often touted as black, although a true black pearl is quite rare. Most have hues of other colours, usually green.
South Sea Pearls
South Sea Pearls are cultured in the waters between Australia and China, using the Pinctada maxima oyster. South Sea pearls can be between 9 and 20mm, some of the largest cultured pearls in the world. South Sea Pearls have a much thicker layer of nacre than other cultured pearls, up to 6mm thick, and have a satiny lustre. Theye in a range of pale hues and are very desirable.
Farmed in the sea around California, Cortez pearls are also referred to as New World Black Pearls. Cortez pearls are produced in the Panamic Black-Lipped Oyster and the Rainbow-Lipped Oyster, which produces highly iridescent pearls. Most Cortez pearls are baroque, with round pearls forming less than 3% of normal yield. Cortez Pearls are the only Fair Trade pearls.
Mabe pearls are the semi-round pearls often seen in jewelery. They are often used in making earrings and rings, and are formed by using a hemi-spherical nucleus during nucleation, and implanting it against the shell of the oyster. When harvested they are referred to as blister pearls, and are worked into Mabe Pearls by cutting away the shell and filling the back with resin. This is then mounted on a mother of pearl back.
Keshi pearls are formed when the oyster rejects and spits out the implanted nucleus before the culturing process isplete, or the implanted mantle tissue fractures and forms separate pearl sacs without nuclei. These pearl sacs eventually produce pearls without a nucleus. Keshi pearls are made of pure nacre, which results in their high lustre. They are generally small in size and, because there was no nucleus to guide the ultimate shaping of the pearl, their shapes vary widely. Keshi may form in either saltwater or freshwater pearls.
Pearl Quality Grading
There is not currently a universal pearl grading system, although two widely used pearl standards are known The first it the Tahitian System.
The A-D System (or Tahitian System) This system grades pearls on a scale from A to D, with A being the highest grade. This is the system used in French Polynesia (based on a government standard there) to grade Tahitian pearls, and South Sea pearls only. It is therefore sometimes referred to as the “Tahitian system.” While this system is standard in producing countries, other markets will still utilize AAA-A.
* A: The highest-quality pearl, with very high luster and only minor imperfections over less than 10% of its surface.
* B: High or medium luster. Surface may have some visible imperfections, but over no more than 30% of its area.
* C: Medium luster with surface defects over not more than 60% of the surface area.
* D: May have many slight defects, but no deep ones, spread over 60% of its surface; or deep defects over no more than 60% of its surface; or abination of minor and deep defects over no more than 60% of its surface. In this grade of pearl, the luster is irrelevant. Even the most lustrous pearls will be graded D if their surface is blemished to this extent. Pearls below D grade are considered not acceptable for use in jewelry.
The AAA-A System
This system grades pearls on a scale from AAA to A, with AAA being the highest grade. This grading scale ismon to freshwater and akoya pearls only, but is accepted by many with South Sea and Tahitian pearls as well:
* AAA:The highest-quality pearl, virtually flawless. The surface will have a very high luster, and at least 95% of the surface will be free from any type of defect.
* AA: The surface will have a very high luster, and at least 75% of the surface will be free from any type of defect.
* A: This is the lowest jewelry-grade pearl, with a lower luster and/or more than 25% of the surface showing defects. In many cases, if the pearl is being mounted into a piece of jewelry, it can be mounted so that the defects are hidden – thus providing a lovely jewelry piece at a lower price.
Pearls are reputed to get better with wear, supposedly as they absorb some of the oils from the skin which condition the pearls. However, harsh chemicals such as deodorant and perfume can damage the surface of the pearls, resulting in lost luster. As pearls are an organic gemstone, they are soft and can be easily chipped, scratched or broken. To care for your pearls the following steps should be taken:
1. Put on any cosmetics and allow them to dry before putting on your pearls. This includes perfumes and deodorants.
2. Wipe your pearls with a soft cloth to remove contaminants after wear. They can be periodically washed in a mild soap solution, and should be rinsed after in running water to remove any residues. Allow them to drypletely before putting them away, as damp in the string may cause rot which could result in breakage.
3. Keep your pearls separate from other jewelery in a box with a soft structured internal form, to prevent them rubbing against each other.
4. Keep an eye on the string, and get them re-strung when it shows signs of wear.
Fake pearls are man made, manufactured pearl look a likes.Often sold a real by unscrupulous sellers, they can be made of a variety of materials which are treated to look like real pearls. Often made of glass or shell, they are then painted, varnished or coated with crushed nacre to simulate the appearance of real pearls. You can tell the difference by performing the tooth test. Drag the pearl gently across your tooth. If it feels smooth its probably fake, as genuine pearls gave a gritty texture from the crystalline structure of the nacre.
Sea shell pearls are manufactured from the shell of pearl bearing mollusks. Making use of the years of nacre build up on the shell, the pearls are ground from the nacre layers on the shell, resulting in a high quality, round, realistic fake pearl. When buying pearls, look out for regional names other than those listed above in the genuine pearls section.
Names such as Mallorca Pearls and Red Sea Pearls are often used to try to disguise the man made nature of the pearls. Its always worth asking the seller to clarify if the pearls are man made, cultures or natural, although a truly unscrupulous seller may dissemble or lie when asked. If you are asked to pay a high price for any pearls, get them checked out by an expert first.