Tagged with 'How pearls are formed'

A Mabe pearl is a composite cultured blister pearl, a large half pearl of glorious nacre that is popularly used for making pearl pendants and pearl earrings.

The Chinese are considered to be the true inventors of the blister pearl, which is a type of cultured pearl. The earliest finds in China of a nacreous layer of pearl grown around a lead image of Buddha have been dated to as far back as the 12th century.

Mabe pearls became better known in the 1950s as an affordable and fashionable way to wear large pearls, for the white South Sea cultured pearls that we have today were widely unavailable. Japanese companies started to produce blister pearls on the Ryukyu Islands between Japan and Taiwan. The word Mabe possibly comes from an old dialect spoken on those islands. Today Mabe pearls are still produced in Japan and China, but also in Indonesia, the Philippines, Thailand and French Polynesia.

Using an adaptation of the process for culturing pearls, a rounded or shaped nucleus is glued onto the inside of the shell of a nacre-producing mollusc. Nacre is the iridescent organic substance that gives pearls their unique properties. The mollusc covers the nucleus as shown in the image above and, after up to two to three years of culturing, the Mabe blister pearls are cut from the shell.  The nucleus is removed and the resulting space is filled with resin, or sometimes a bead, and the back of the pearl is sealed with a piece of mother of pearl. The final result should be a beautiful silky pearl of between 12 and 25mm in size.

Mabe pearls are often associated with a traditional style of round pearl earring such as those seen in Meryl's Streep's publicity images for the film 'The Iron Lady'. They are also used by designers to make imaginative pieces of distinctive and contemporary pearl jewellery, with their colour and inexpensive sizes being two major factors in their continuing popularity.

Have you wondered how long it takes to grow a real cultured pearl? Is it a month, a year or perhaps longer? The answer? Of course it depends...

The delicate process of culturing pearls

Pearl farmers start the process of producing a cultured pearl in an oyster or mussel by delicately implanting a small piece of mantle tissue, the part of a mollusc that secretes shell-like material. Farmers might also add a bead of shell, typically from a freshwater mussel to help provide a nucleus for the pearl.

If this complex procedure is successful, the mollusc will start to deposit iridescent layers of nacre, slowly creating a cultured pearl.

One of the first factors that influences the growth of a cultured pearl is how quickly the mollusc recovers from the implantation procedure itself. This is a particularly sensitive time. Before the growth stage of a pearl, the operated mollusc will need care and attention from the pearl farmer.

Image: Cultured pearls

In the case of Japanese Akoya oysters, this care period lasts up to six weeks, as much as three months for a large Tahitian and South Sea oyster, but for Freshwater pearl mussels this care period can be as short as about two weeks.

If you are interested in the differences between the different types of pearls, learn more in our Buying Guide here.

Nacre growth rates

Once the mollusc has recovered, it is returned to the pearl farm population, where the main period of growth of the cultured pearl will take place.

Depending on the type of mollusc, the water cleanliness, temperature and the time of the year will all influence the rate at which the mollusc deposits its nacre to grow a cultured pearl.

During this time, the molluscs will be regularly inspected by a pearl farmer, checked for sickness and cleaned of parasites. The farmer will also closely monitor environmental factors such as water temperature, food quality and any risks of pollution.

The growth rate of nacre can vary widely with around 0.3mm of nacre a year for Akoya pearls, up to 2mm a year for Tahitian and Australian South Sea pearls and as high as 5mm per year for Chinese freshwater pearls.

Nucleation is also a factor in a pearl's size

For non nucleated pearls, which did not initially have a bead of shell implanted, a simple rule is that the longer a pearl is grown in the mollusc the larger the pearl.

Typically, non nucleated Chinese freshwater pearls can quickly grow to maturity over periods as short as 6 months, reaching sizes up to 9mm in diameter within 24 months.

Image: An operation by a pearl farmer to culture a pearl

This simple rule may not be true for nucleated pearls, however, as their size is also influenced by the diameter of the implanted shell bead and how many culturing operations the oyster has had.

Typically, an Akoya pearl will grow between 10 to 14 months before reaching a size of up to 9mm in diameter, a Tahitian pearl may grow for 18 to 24 months to reach a size of 10mm and a South Sea pearl will grow between 2 and 3 years to reach diameters of up to 15mm.

For nucleated pearls, the thickness of the nacre is often a reliable measure of how long each pearl has been cultured and its quality.

A complex partnership with nature...

So to answer the question, there are many factors that determine the size of a real cultured pearl and how long it will take to grow in an oyster or mussel. It is an amazing and complex process that relies on the skill and expertise of the pearl farmer and their partnership with nature.

If you are interested in learning more about the different qualities of a pearl, why not read our Buying Guide to Pearl Grading.

Fashioned with oddly shaped pearls, we have just introduced our first Keshi pearl necklace and matching Keshi pearl bracelet to Winterson.

The word keshi or keishi means ‘poppy’ in Japanese. This pretty word perfectly captures the shining lustre, orient and baroque shape of Keshi pearls, which lend themselves to distinctive jewellery.

Keshi are thought to form naturally in a saltwater oyster, as a piece of trapped tissue, shell or a micro-organism causes the growth of a baroque pearl. With no implanted bead nucleus, they are composed entirely of nacre and this gives rise to their beautiful shine.

In recent years with the growth of the cultured pearl industry, Keshi pearls have been produced in saltwater oysters by accident when the inserted nucleus separates from its tissue implant. The term Keshi is also widely used by producers of Chinese cultured freshwater pearls to describe baroque pearls that are produced spontaneously in the mussel after the first harvest of pearls.

Let us know what you think.  We hope you like them !

The astonishing diversity of the pearl has made pearls a versatile gem of choice for all types of jewellery, in fashion and other accessories. But when buying and wearing pearls, should you pay attention to its shape?

The shape of a cultured pearl is determined by several factors when the pearl is developing inside the mussel or oyster. The most important of these are the shape of the nucleus used by the pearl farmer and the position of a pearl that is grown in the mollusk.

Gemmological experts at the GIA describe the shape of pearls using three categories.

1. A spherical pearl has a round or near round shape. This is the classic pearl shape. Perfectly round pearls can be quite rare, particularly with Freshwater pearls that tend to be near round as they are not grown around a bead.


2. A symmetrical pearl has a regular shape so that, if it is sliced in half, each half is a mirror image of the other. These pearls can have an oval, flattened button or drop shape.


3. A baroque pearl has an irregular and non-symmetrical shape. Pearls are described as semi baroque if they are not quite symmetrical.

Certain pearls also have grooves or ridged rings around their entire circumference and these pearls are referred to as circled.

The value of these pearls can vary widely, with a round pearl being generally considered the most valuable shape of a pearl. Perhaps traditionally this was because pearls were considered to be a symbol of the moon. But today, rarity and perfection are key drivers of value in a cultured pearl. For these reasons we would recommend that you buy pearls from a recognised pearl specialist.

Is shape a good guide to pearl quality? Not entirely. We love the quality and look of baroque pearls. Whilst not as valuable as round pearls, they can still make a highly individual and unique piece of jewellery.

There are also other important factors you should consider when buying pearls such as Lustre and Surface.

If you hear a pearl described as real or natural, remember that there is a significant difference in meaning.

A natural pearl is a real pearl formed in a wild mollusc living in its natural habitat and without any human intervention. Cultured pearls are also real pearls, but the pearl farmer stimulates the development of the pearls in the mollusk.

Natural pearls have been collected and used in jewellery for centuries. Until the introduction of techniques for culturing pearls in the early 20^th century, the world’s main natural pearl fisheries could be found in the Persian Gulf, the Gulf of Mexico, the Mannar Straits between India and Sri Lanka, and off the coast of California.

The image of a diver searching for pearls in azure blue tropical waters is a symbolic one, as today there are few fisheries left due to over-fishing, pollution and competition from the cultured pearl industry.

In response to increasing demand and limited supply, the value of rare natural pearls has been rising steadily over the last ten years.  A natural pearl necklace can be priced at between 100 and 10,000 times the value of a cultured pearl necklace of the same size, weight and lustre.

When describing the shape of a pearl, baroque is a term that is used to describe irregular and non-symmetrically shaped pearls that have been formed in freshwater mussels and saltwater oysters. Baroque pearls are not round, drop or button shaped.

The shape of a baroque saltwater pearl is caused by the uneven deposition of nacre by the oyster around its nucleus.

Up to 40% of the harvest of cultured pearls from a Tahitian pearl farm can be baroque in shape. These generally are found to be smaller in size, with true Tahitian baroque pearls greater than 12mm being very rare and sought after.

Larger Australian South Sea baroque pearls are also unusual and particularly beautiful, with a silver blue overtone and beautiful lustre.

Baroque pearls have been used for many years to create wonderful pieces of jewellery. One of the most famous historical pieces of baroque pearl jewellery is The Canning Jewel. To be found today in London’s Victoria & Albert Museum, it is believed to have been made in the 19^th century and uses a number of baroque pearls to create its mythical Merman figure.

Baroque pearls today are less extravagantly worn, but are still highly sought after for their individual shapes and colours. Today, baroque pearls are inspiring a new generation of contemporary fine jewellers, from Melanie Georgacopolous to Mizuki, drawn to their unique forms.

At Winterson, we stock a range of necklaces, baroque pearl earrings, sautoirs and bracelets made from Tahitian baroque pearls. Each pearl is unique and its contours, circles and peacock colour creates a sophisticated and highly contemporary look.

The commercial sale of fake, faux and artificial pearls is quite common and many customers ask us about pearls that they have seen or been offered on holiday. For example, no pearls are cultured in Mallorca.

The techniques for creating imitation pearls were first developed in 17^th century France and the basic procedures are still in use today. A fish paste called ‘Essence of the Orient’ was made from salmon and herring scales, mixed with varnish and used to coat a hard bead such as alabaster or glass.

The resulting ‘pearl’ was dried and polished, before the process is repeated many times to form imitations of the layers of nacre that are found in a natural and cultured pearl.

Typically, these ‘pearls’ are uniform in appearance and don’t have the unique characteristics of colour, shape and blemishes that you will find in natural or cultured pearls that have been grown in a mollusc. More recently, better examples of fake pearls can be found.

We love the deep lustre of natural and cultured pearls. None of the pearls that we sell at Winterson are made using these imitation techniques.

If you have any questions about our jewellery, please do contact us.

A pearl's iridescence is known as lustre and is absolutely unique to pearls, different to any other gemstone. When grading pearls, highly prized pearls will have strong depths of colour and a shiny lustre. Without lustre, pearls can be dull, opaque and lifeless.

The factors that determine a pearl’s lustre are highly complex, being determined physically by the way that light diffracts through the physical structure of the layered nacre of the pearl. The thickness of the nacre is caused by how long the pearl is left in the oyster. Generally, pearls with the greatest thickness of nacre will have the deepest lustre.

The colour of a pearl mainly reflects the type of oyster or mussel that the pearl was cultured in.  However, a pearl’s complex overtones of colour can also be due to the temperature of the water, its cleanliness and even the plankton that the oyster feeds on. For example, colder water can introduce a light grey colour to a pearl and dirty water will create a brown overtone.

Unfortunately once the pearl is removed from the oyster, lustre doesn’t improve with age like a fine wine.

By selecting good quality pearls, and with careful cleaning, the lustrous qualities of a beautiful pearl can, however, be maintained over time. For more information, read our Buying Guide on how to take care of your pearls.

Following the invention of the cultured pearl, a revolution began to take place in the world of pearls. Pearl diving and over-fishing in the late 19th century had driven prices of natural pearls soaring.

The advent of techniques for culturing pearls in saltwater oysters brought these fabulous gems within the reach of many, without depleting further the world’s natural mollusc beds. The method used for the creation of a cultured pearl is still widely used today.

A small round bead of shell material from a mussel and a piece of nacre-producing tissue from another oyster is inserted into a saltwater member of the Pintadine shellfish family. This highly skilled procedure is called a graft.

The nacre-producing tissue forms a small pearl sac around the bead and then gets to work covering the irritant with layers of nacre. Once the process has started, the pearl farmer has little control over of the final size, shape and colour of the pearl produced.

Once grafted less than 5% of these Pintadine shellfish, commonly referred to as oysters, go on to produce the best quality cultured pearls. Each pearl is unique and individual.

Today these grafting techniques are used in countries such as Japan, Indonesia and Australia to produce a wide variety of cultured pearls in both saltwater and freshwater molluscs.

This amazing diversity has inspired new directions of pearl jewellery and fashion beyond the classic white pearl necklace.

The next articles in this series will look in turn at the many different types of cultured pearl, in particular Freshwater, Akoya, Tahitian and South Sea pearls.

A natural pearl might start with an itch, although most pearl experts now agree that the 'grain of sand' is nor more than a myth.

When a small seed of material such as a parasite becomes trapped within an oyster or mussel's shell, nature gets to work. The shellfish slowly deposits layers of organic material called nacre around the source of its irritation.

Nacre is made from two forms of calcium carbonate called Aragonite and Calcite, which are found in the interior lining of shellfish that is often called ‘mother-of-pearl’. These are linked together by a little organic protein called Conchiolin, which is identical to that found in human hair and fingernails. Together these substances form the nacre.

Over time, layering of this nacre by the shellfish forms a smooth surface around the foreign material slowly transforming it into a beautiful pearl, unique in its shape, size and colour. The difference from one pearl to another lies in the shape and placement of crystals of Aragonite and Calcite that are being held in place by Conchiolin.

In our next articles we shall look at the differences between natural and cultured pearls.