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The production of pearls and their main types
Pearls are found in the shells of mollusks like oysters and clams. They can either be naturally occurring or created in pearl farms. Their ultimate value and price depends upon a number of factors like size, shape and lustre. In the following article, the reasons pearls are produced by mollusks as well as the main method by which cultured pearls are formed are explained. Apart from their types, their importance to the jewellery business is also mentioned.
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A pearl is a smooth spherical object obtained from inside mollusks like oysters and clams. Pearls are known for their translucent white or the rare, more expensive, black shiny coating. These tiny globes are made up of the same matter as the mollusk's shell – calcium carbonate - only they are round in shape and may not initially appear to be the same. While most mollusks may be able to produce pearls, not all are considered of gemstone quality.
How Pearls are formed
As mentioned above, a pearl is produced within the shell of a mollusk. This beautiful object is formed when something in the water (parasites usually) gets into the mollusk's shell while it is open (for obtaining food or breathing). This becomes an irritation for the mollusk who in turn starts to produce a pearl sac to protect itself from the invader. It is widely believed that sand gets inside the shell to start off the pearl production process. This actually happens very rarely. With the passage of time, the pearl sac will harden and become a pearl. The shiny shell-like surface of the shell is made up from a combination of minerals collectively termed as nacre resulting in 'nacreous pearls'. The calcium carbonate found in nacre will easily dissolve in any acid solution, like vinegar which contains acetic acid. Pearl lustre depends on the number of layers in the pearl. It is not uncommon for any type of pearl (natural or cultured) to be dyed other colours – black, purple, green, yellow, blue and pink.
In the past, the only way to obtain pearls was to capture and kill a large number of these pearl-producing mollusks to see whether anything was inside. As a result, pearls were once extremely expensive to own.
Different types of Pearls
The most valued and sought after pearls are those found naturally. However, the world market is filled with a number of possibly cheaper (in both price and quality) pearls.
1. Natural Pearls - These are the rarest of all pearl types – the ones found in nature and not assisted in any manner by mankind. These pearls can be any shape, but exact round ones are extremely rare and hence very pricy. Natural pearls are produced either by freshwater inhabitants like freshwater mussels in ponds, lakes and rivers or by saltwater creatures like the pearl oyster which lives in the sea. Like other precious gems, the value of a pearl depends on factors like shape, size, colour, quality and lustre. In expensive jewellery, the pearl will usually be accompanied by other precious stones. Natural pearls are identified though X-ray examination. Other mollusk species may be capable of producing pearls, but these have little or no value at all because they lack lustre and durability. There are other species that produce blue, pink and orange pearls. However, these are very rare and are greatly valued as they are naturally lustrous. Giant clams have been known to produce large pearls – the largest one ever seen came from the Philippines (1934) and weighed a whopping 6.4 kgs!
2. Cultured Pearls - Cultured pearls make up a majority of the current world pearl market. These pearls are cultivated or 'grown' in pearl 'farms', where human intervention mixes with natural production. Here, a small part of the tissue producing the pearl sac is placed into another mollusk shell. Sometimes a round bead (made from shell material) may be added to the new shell. The layers of nacre are then produced by the oyster around this bead, thereby following its shape. Most Black Pearls, cultivated from the black pearl oyster are not really black and may be purple, green, blue, grey or a mixture of colours.
3. Imitation Pearls - This cheapest variety of all pearls is simply manufactured from shell material or glass which is then covered with a fish-scale solution. They are usually easy to identify if placed next to a real pearl and studied under a microscope.
The importance of Pearls in society
1. Jewellery - Pearls are of special importance in the jewellery industry, where only the most lustrous ones are valued. Size and shape of the pearl also matters. Round pearls are given greater consideration, but other shapes also figure commonly in pearl jewellery. These include the flat round button pearls, the ones shaped like drops, oval pearls and most recently 'rice' pearls (similar in shape to grains of rice). Pearls were once also incorporated into fancy (and expensive) clothing.
2. Religion – Pearls are symbolic of many deities and events occurring in a number of religions. They are of significance and sometimes even directly referred to in Hinduism, Judaism, Christianity and Islam. Pearls can stand for something pure and rare, as well as a symbol of someone's vanity and pride. The gates of heaven are also popularly known as the "Pearly Gates".
3. Other uses – In the cosmetic and medicine industry, sometimes crushed pearls are used.
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