Natural Pearl Guide
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How are pearls formed?
An oyster becomes irritated by a nucleus often in the form of a piece of shell or sand which it then begins to coat with calcium carbonate in the form of a lustrous nacre hence creating a pearl. The longer the irritation remains the bigger the pearl will become but many pearl farmers tend not to grow pearls over 12mm and put more time into ensuring the pearls are of the highest quality rather than going for a larger size.
What is a nucleus?
A nucleus is the very centre of a pearl and can be natural in the form of some sand, grit or a piece of shell or it can be artificial. Mississippi pig-toe mussel shells are commonly carved into shapes and used as a nucleus which are created by a variety of firms, in particular the Japanese have become renowned for the quality of shell bead they produce.
Has does a nucleus end up in a pearl?
It can either by inserted into the pearl which is not an easy task and requires great skill or with naturally occuring pearls the nucleus whatever it may be finds it wat inside the pearl all on its own.
How are pearls cultured?
First off oysters are gathered in order to be used in creating the pearls. Once prepared a process know as seeding takes place where the nucleus wether it is natural or a bead is inserted into the oysters gonad. This is a delicate process which can take many years to master. A long process of cleaning and servicing the oysters then takes place over what is generally a 2 year period in order to keep the oysters healthy and producing the best pearls possible. Mabe pearls are created in a slightly different way and are grown on the inside edge of the oysters body where a hollow normally plastic shape is attached which then acts as a nucleus.
What makes one pearl better than another?
There are five main factors that determine a pearls quality:
1. Luster - the surface brilliance and shine.
2. Shape - perfectly round pearls are the most valuable and are very rare especially in large sizes.
3. Colour - white/cream are the most common colours but many other colours also occur naturally such as black and pink (this refers only to natural colouring and not pearls which have been dyed).
4. Surface Quality - how smooth the pearls surface is.
5. Surface Thickness - how thick the actual nacre layer on the nucleus is.
There are exceptions with pearls now being grown in a wide range of shapes including crosses, sticks, coins and many more. The best pearls are produced in clean nutrient rich waters with stable temperatures, tides and a good flow of water to wash waste away that is produced by the oysters. All of these things minimise stress which generally results in the pearls produced having only minor flaws or none at all. Another influence on the quality of pearl produced is the pearl farms location with the closer to the equator a farm is the lower quality the pearls they produce. Australia has some of the best pearl farming waters in the world.
There are two main pearls grading systems A-AAA and A-D this can be very confusing for buyers as the lowest grade in one system equals the highest grade in another system. The other major problem is that pearl grading is generally according to opinion. In the first system A-AAA, A is the lowest grade and AAA is the highest grade this is system used by the Chinese although they may occasionally use the A-D system. The second A-D system is generally used in grading saltwater pearls such as Tahitian and South Sea pearls with A being the highest grade and D being the lowest.
Freshwater pearls are grown in rivers and lakes in mollusks such as mussels rather than Oysters and are not bead-nucleated and instead upto 50 small incisions can be made in the fleshy mantle tissue where a piece of flesh from another mollusk is then inserted. Allowing a freshwater mollusk to produce upto 50 pearls at a time. It is because freshwater pearls have no foundation in the form of a nucleus that they are very rare perfectly round. In general freshwater pearls have a lower quality lustre than their saltwater counterparts but the Chinese in particular have really perfected the freshwater pearl culturing process and are now producing perfectly round pearls in very large sizes sometimes over 16mm that are barely indistinguishable from the more expensive saltwater pearls.
Originally farmed primarily in Japan, Akoya pearls are those which are harvested from a particular oyster breed Pinctada fucata martensii and are generally the most consistently round or near round pearls. Due to great competition and improvement in the pearling techniques used by the Chinese the Japanese now focus on producing the larger Akoya pearls around the 8-11mm with nacre 0.35-0.7mm thick which are not commonly seen in China because the Akoya pearls are grown in one of the smallest oysters used for pearling it makes producing larger sized pearls that much harder. The Japanese now import many of the smaller Akoya pearls from China drill them and treat in Japan doing just enough to allow them to label them as Japanese.
Tahitian pearls contrary to popular belief are not actually from Tahiti the Island itself has no Pearl farms whatsoever and instead is the trading capital for Tahitian pearls which actually come from throughout French Polynesia. The black-lipped oyster Pinctada Margaritifera produce the ever popular Black Tahitian pearls, which in most cases are not in fact black instead are shades of grey, charcoal and silver with true Black Tahitian pearls being very rare. The black-lipped oysters are some of the largest used to grow pearls and can measure over 30cm / 1 foot long and can weigh upto 10 pounds / 4.5kg.
South Sea Pearls
South are produced in the waters between the southern coast of China and the northern coast of Australia home to one of the largest oysters used in pearls culturing the Pinctada Maxima which comes in two varieties silver-lipped and gold-lipped. The average sizes pearl produced is 13mm and they generally range between 9-20mm and have a very thick layer of nacre 2-6mm. There are several factors as to why they grow so much bigger than other pearls:
The larger oyster can take a bigger nucleus than its counter parts.
Due to the clean fertile waters the oysters live in they produced nacre at a faster rate.
The oysters can spend a longer period of time growing the pearl - generally around 2 years.
Keshi pearls are generally small in size, very lustrous, irregular in shape and are becoming harder to find. Keshi pearls form when the nucleus is rejected from an oyster or the mantle tissue inserted into a mollusc fractures and causes seperate sacs of nacre to form. As there is no foundation for the nacre to take shape the pearls can come out many different irregular shapes and it is because there is no nucleus that the pearls are normally extremely lustrous as the are made from pure nacre.
How to tell real pearls from synthetic pearls?
One quick and easy test is run a pearl lighter along one of your teeth synethic / manmade pearls will fell silky and smooth where as natural pearls will feel gritty similar to a stone but please be sure if they aren't your pearls to get permission before doing this.
If you have any questions please feel free to contact me and I will do everything I can to help.