Types of Pearls
Types of Pearls by George Collins
There are several types of pearls that differ greatly in colour, size, shape, and place of origin. Not all types of pearls are perfectly round and creamy. Pearls are mainly classified two types: natural pearls and cultured pearls. Over the history, natural pearls have become increasingly rare as they have been harvested at an incredibly rapid rate. In fact, the most types of pearls sold nowadays are “cultured pearls” – they have formed only due to human intervention. They are real pearls, but they’ve not occurred naturally.
Natural pearls grow without any human intervention, whereas cultured pearls form when a farmer inserts a mollusk into the oyster shell. For natural types of pearls, the mollusk is an organism in the water. For cultured pearls, the mollusk is usually a tiny bead. Natural pearls look more “organic” than cultured pearls. For instance, they may not be as well-shaped or as round as their cultured pearl counterparts. Natural pearls are extremely rare and most of them have already been harvested. That’s why natural pearls are very expensive and almost impossible to locate—with most being sold at antique auctions.
Cultured pearls, on the other hand, are not incredibly rare. Cultured pearls are the types of pearls used to make almost all jewellery on the market today.
To begin growing a cultured pearl, technicians must implant a small section of shell along with mantle tissue from similar molluscs into an oyster. They are then carefully returned to the ocean in individual mesh pockets and left to secrete layer after layer of glossy nacre that eventually forms the pearl. The oysters are periodically brought onto land for cleaning and a health assessment. Pearl technicians take every conceivable measure to protect the oysters from disease and damage.
Cultured pearls are a beautiful gemstone and are produced in both freshwater and saltwater. Freshwater pearls grow in rivers, lakes, reservoirs, and ponds. Most of them come from China. Saltwater pearls are grown across Australia and Asia. There are three main types of saltwater pearls: South Sea pearls, Tahitian pearls, and Akoya pearls. Saltwater pearls are usually considered more valuable than freshwater pearls. Cultured pearls can be a variety of shapes, including oval, round, semi-round, pear, baroque, button, drop, and circle. Most pearls are white or black, but you can find pearls in other colours such as pink, green, and silver.
Types of pearls
CULTURED SALTWATER PEARLS
Cultured saltwater pearls are grown in saltwater when a mollusk is implanted in a saltwater oyster shell. Saltwater pearls are grown across countries and islands in Asia and Australia. There are three types of saltwater pearls: Tahitian pearls, South Sea pearls, and Akoya pearls. These types of pearls range in size from 2mm to 15mm diameter. They’re most often round and white but can be black or pastel colours.
In general, saltwater pearls are more expensive than freshwater pearls because they take longer to cultivate. A saltwater mollusk only produces a single pearl at a time, whereas freshwater oysters can grow up to 30 pearls at once. Saltwater pearls make for beautiful jewellery—particularly earrings, necklaces, and bracelets. Because pearls are less durable than diamonds and coloured gemstones, pearl engagement rings are rare.
As the name suggests, this type of pearl is grown inside freshwater mussels as opposed to ocean molluscs. They are the most affordable and common type of pearl on the market, although the finer specimens can still reach a hefty price.
Freshwater pearls hail primarily from China and can vary greatly in colour. Typically, they come in pastel shades of peach, lavender, pink, and white. They are often treated with special dyes to enhance or change their colouring. Freshwater pearls dyed black are known as “Peacock pearls” due to their shimmering violet iridescence. Freshwater pearls can range in diameter from 2mm to 12mm, with some new types reaching up to 15mm. Let us talk about how to identify different types of pearls and how to distinguish them from one another.
The image that comes to mind for many people when thinking of pearls is likely that of the Akoya pearl – the characteristic luxurious white sheen is exclusive to this type of pearls. Akoya pearls are farmed using the Pinctada fucata martensii saltwater oyster found in the colder coastal waters of Japan, Vietnam, and Southern China.
Japan has long been the world leader in the cultivation of Akoya pearls, producing the most consistently high-quality specimens in the world. While Akoya pearls are typically white, some may possess golden or silvery-blue undertones. Akoya pearls usually are found in white, gray, green, pink, and blue (although rare). Most Akoya pearls are round. Akoya pearls are known for their bright luster and elegance. Akoya pearls typically range in size from 2mm to 9mm, with the biggest and most valuable reaching up to 10mm (although this is exceedingly rare).
Tahitian pearls are harvested from black-lipped oysters in the temperate coastal waters of French Polynesia. They are known for being the only naturally occurring “black pearls” – typically sporting a glossy, metallic, grey colouring. Darker pearls are less common than lighter once and therefore fetch a higher price. This type of pearls are prized for their size as well as unique colouring, ranging from 8mm to 18mm. Tahitian pearls that exceed 15mm are quite uncommon and fetch outrageous prices. Any Tahitian pearl under 0.8mm is too small for export. Tahitian and South Sea pearls are the only types on the market that never receive any form of colour treatment after harvest. Their exceptional colouring and lustre are what makes them so popular.
South Sea Pearl
These highly sought-after treasures are typically the largest and most expensive type of pearls. Part of their mystique is the fact that they are grown in the infamous “coral triangle” – a section of treacherous water that lies between Australia, Indonesia, and the Philippines. South Sea pearls range in size from 8-20mm, with pearls larger than 15mm going for tens of thousands of US dollars. Depending on the type of oyster they form in, they can be a silky white (similar to an Akoya), a sleek silver, pastel pink, or a rich gold.
Large, perfectly round South Sea pearls are unquestionably the most prized and valuable types of pearls on the market, which is why people are prepared to go to drastic lengths to farm them.
Baroque pearls come in different shapes and sizes. Pearls are assessed by numerous factors, the key one here being shape. There are two primary shape categories that all pearls fall into: traditional and baroque. Traditional pearls are round, while baroque pearls are virtually anything else. Some prefer baroque pearls for their unique shapes, although traditional pearls are generally more valuable. The price of a traditional pearl depends on its size – the bigger, the better. Baroque pearls fetch higher prices based on colour and sheen. Since the white and pink baroque pearls are far more common, patrons will spare no expense to obtain the darker ones.
Baroque Pearls Are Further Classified By Their Shapes:
As the name suggests, two pearls have fused to form one. They can be symmetrical or mismatched, and they are favoured among jewellers for crafting stud earrings.
This type of pearls are characterized by their flat, round shapes and smooth, reflective surfaces. They are used in all sorts of jewellery, from necklaces, to earrings, to bracelets and beyond.
This type of pearls are typically small, rounded specimens that do not meet the strict spherical dimensions of traditional pearls.
Resembling the shape of an eggshell, these bottom-heavy pearls are generally used in hanging jewellery. The jeweller will drill down through the centre of the egg pearl to best display its unique shape.
Like coin pearls, heart pearls are flat, reflective specimens that have also formed into the shape of a heart. They are popular when creating romantically themed pieces of jewellery.
One of the rarest types of baroque pearls is Keshi pearl. Keshi pearls occur when the oyster rejects part of the seed but carries on developing the specimen. They are typically elongated pieces of nacre that bear a remarkable lustre.
Pearls are fabulous and fascinating, and they make wonderful gifts, either for someone else, or if you want to spoil yourself. They’re especially suitable for 30th anniversary gifts, also known as the pearl anniversary. Now that you know more about the different types of pearls, you can choose the ones that appeal to you most.
Factors that affect pearl quality
There are three main types of pearls used in jewellery:
South Sea (White, Golden and Tahitian)
Each type of pearl is produced by a different species of oyster and each oyster lives in a different region of the world under very specific climatic conditions.
Pearls are unique among gemstones in that they are natural, organic products of living creatures, so they have different grading standards. Seven factors determine the quality, value and beauty of pearls: size, shape, colour, lustre, surface quality, nacre quality and matching. A pearl’s ultimate size and quality can depend on several variables – the size and health of the mollusk that produced the pearl, the size of the nucleus and the amount of time the mollusk spent underwater adding layers of nacre to build the pearl. Other factors also include the climate and the nutrient conditions of the mollusk’s growth environment.
Keshi pearls are a shape rather than a type of pearl as is commonly believed. They are formed when the oyster rejects and spits out the implanted nucleus before the culturing process is complete, or the implanted mantle tissue fractures and forms separate pearl sacs without nuclei. These pearl sacs eventually produce pearls without a nucleus. Keshi pearls can form in either saltwater or freshwater mollusks.
They are generally small in size and because there was no nucleus to guide the ultimate shaping of the pearl, their shapes vary broadly. Keshi pearls come in a wide variety of colours and tend to have high lustre and even orient. This is due to their solid-nacre composition – the implanted nucleus of the pearl has been expelled by the mollusk resulting in 100% nacre. This gives it an especially lustrous and shimmering surface quality. Most keshi pearls, in fact, have a greater lustre than even the best-quality cultured pearls. The fact that keshi pearls are solid nacre does not, however, give them the classification of natural pearls. This is because keshi are a bi-product of the culturing process, not a natural occurrence.
Keshi pearls, especially South Sea keshis, were once quite the bargain yet beautiful and unique pieces. Today South Sea keshi pearls are much rarer. This is because South Sea pearl farmers are now x-raying oysters to determine whether or not the nucleus has been expelled. When a nucleus-free oyster is found they are re-nucleated before a keshi has time to form. This practice has made South Sea keshi pearls much harder to find than was once the case. Keshi means “poppy seed” in Japanese and these pearls are often also referred to as “poppy seed pearls.”
Pearls are measured by their diameter in millimetres. Tiny seed pearls can be smaller than 1mm, while South Sea pearls, as large as 20mm, have been found. If all other quality factors are equal, the size of a pearl will determine its value. Only a 1 millimetre increase in pearl size will be a substantial jump in both appearance and value. The importance of a pearl’s size to its ultimate value depends on the pearl type. If a high quality pearl is larger than usual for its type, it will be worth more than smaller pearls of the same type. The average pearl sold today is between 6.5mm and 11mm.
As pearls are natural organic gemstones, they can occur in a wide variety of shapes, many of which are quite unique and interesting. The round pearls you most commonly see are by no means the only shape in which pearls are found!
Indeed, perfectly round pearls are actually quite rare. This is because the eventual shape of the pearl is determined by a number of highly variable factors which occur inside the oyster as the pearl is developing. For example, the pearl often assumes the same shape as its nucleus (the irritant which was placed inside the oyster to initiate the formation of the pearl which guides the process of the pearl shape). If the nucleus is not perfectly round, the resulting pearl is likely to reflect this irregularity.
In addition, the pearl’s positioning within the oyster also plays a role in determining its shape. If, for example, the pearl develops against the shell it will become more flattened on that side. Some pearls develop with one or more grooves or rings encircling them. These pearls are known as ringed or circled. The primary shape of a pearl is, therefore, described as circled round or ringed oval. These circles or rings may occur if constant pressure is placed against the pearl as it is developing within the oyster.
There are 8 basic shapes:
Round pearls are perfectly spherical – the shape most people think of when they think of a pearl. Due to their relative rarity and “classic” nature, they are highly desirable. Round pearls fall into the spherical category.
These pearls are not perfectly round. Instead, they are slightly flattened or elongated rather than being a perfect sphere. Nonetheless, they are so nearly perfect that they, too, are classified as spherical.
This type of pearls are semi-round, similar to near round.
These pearls are shaped like an oval – narrower at the ends than they are in the centre. Ovals are categorized as a symmetrical shape.
Button pearls are flattened to some degree, making them resemble a button or perhaps a disk rather than a perfect sphere. These pearls are often used in earrings where the flattened side can be attached to the setting. Buttons are also categorised as symmetrical.
Drop shaped pearls are pear or teardrop-shaped. The drop can either be “long” or “short” depending on its proportions. These pearls make attractive earrings or pendants. This is also a symmetrical shape.
This is a pearl which is both non-symmetrical and irregular in shape. The baroque pearl can be purely abstract in its shape or it can resemble a cross, stick or some other shape. Baroque pearls fall into the baroque category.
These pearls are slightly irregular in their shape. For example, a pearl which might otherwise be considered an oval, button or drop pearl but which is not symmetrical in nature, would be considered semi-baroque. Semi-baroque pearls fall into the baroque category.
The shape of the pearl is one of several factors which goes into determining its quality and, therefore, its value. In general, round and near-round pearls are the most valuable due to their rarity. Symmetrical shapes are generally considered to be more desirable than baroque shapes. Baroques, however, can be extremely unique thus increasing their desirability more than might be expected based on their shape alone. A perfectly round pearl is very rare. The rounder the pearl, the more valuable it is. Baroque pearls are not symmetrical in shape and can be lustrous and, therefore, just as appealing as their round counterparts.
A pearl’s colour contains three basic components – hue, the colour’s first impression; tone, its lightness or darkness; and saturation, its strength or intensity. Pearl colours tend to be muted displaying a broad range of subtle hues. A pearl’s colour can have three main characteristics:
Body-colour – the dominate overall body colour of the pearl.
Overtone – one or more translucent colours that appear over a pearl’s body-colour.
Orient-iridescent – rainbow colours shimmering on or just below a pearl’s surface.
Pearls come in a variety of colours from white to black and every shade in between. All pearls display body-colour but not all pearls will display overtones or orient. It is important to distinguish between colour and overtone. For example, some naturally occurring colours are white, champagne, aqua, green, golden and black. Within each colour category there are a number of common overtones or subtle variations in the surface iridescence. Overtones are translucent colours which sometimes appear over top of a pearl’s main body-colour. These overtones tend to alter the body-colour somewhat as well as adding depth and glow. For example, a pearl may be white with rose overtones.
Some pearls have no overtones at all while some display an orient that shows a rainbow iridescence which is an incredibly rare factor only seen in approximately .01% of pearls produced today. The term orient refers to the shimmering, iridescent colours which appear to move and glitter when the pearl is turned. This phenomenon is caused by the way in which light is reflected through the various thin layers of nacre which make up the pearl.
Lustre is the most important of all the value factors when considering the beauty of a pearl. Lustre is more than a combination of surface brilliance and a deep glow. It is caused by light travelling down through the translucent layers of nacre and reflecting back to the eye from deep within the pearl.
The translucence and arrangement of the overlapping nacre plates are more important influences on whether or not a pearl will have high lustre. With a good quality pearl you should be able to feel the difference and see your reflection on the surface. Growth conditions can influence the lustre of a pearl, for example, the quicker the nacre is produced, the less translucent it is likely to be. As a result, the nacre may be thick but not lustrous.
There are four categories of lustre:
Excellent – reflections are bright, sharp and distinct.
Good – reflections are bright but not sharp and they are slightly hazy around the edges.
Fair – reflections are weak, hazy and/or blurred.
Poor – reflections are dim and diffused.
The highest quality pearls have a sharp, mirror-like lustre showing a high level of reflection.
Pearl surface quality
Pearls are organic so it is not surprising that they show surface qualities. The cleaner the surface of the pearl, the more valuable it is.
There are four classifications:
Clean – pearls can be blemish free or contain minute surface characteristics that are very difficult to see.
Lightly Blemished – minor blemishes or surface irregularities.
Moderately Blemished – noticeable surface characteristics.
Heavily Blemished – obvious surface irregularities.
pearl nacre quality
Nacre is the very essence of the pearl itself. It is the natural substance that the mollusk secretes to protect its sensitive flesh from irritants such as shell fragments or implanted beads. Nacre is made up of thousands of layers of thin overlapping crystal plates with irregular edges. This is the same beautiful iridescent material that lines the inner surface of the oyster shells. A pearl’s appearance helps determine its quality which has a lot to do with whether the nacre is thick or thin, although thick nacre does not always indicate a highly lustrous pearl.
Nacre quality can be classified in three ways:
Acceptable – nucleus not noticeable, although slight blinking might be present. No chalky appearance.
Nucleus Visible – the pearl shows evidence of its bead nucleus through the nacre.
Chalky Appearance – the pearl has a dull chalky appearance.
The lustrous outer surface, or nacre, of natural and cultured pearls is made up of the same nacreous material. Its chemical composition is about 90% calcium carbonate; the rest is water and organic materials.
Pearl nacre is composed of microscopic crystals. The crystals are aligned perfectly so that light passing along the axis of one is reflected and refracted by the others to produce a rainbow of light and colour. The iridescence that we commonly associate with pearls is produced by the particular arrangement of the nacre layers. The size and shape of a cultured pearl is determined by the size, shape and position of the implanted nucleus. The size, shape and colour of a natural pearl is determined by the type of irritant, the water condition and food supply. The general health and wellbeing of the oyster will also determine how lustrous the nacre of the pearl will be when harvested.
Pearl matching is more important when considering a strand of pearls. Minor variations between pearls within a strand should be expected as no two pearls are identical. When considering pearl matching, uniformity of pearl factors such as size, shape, colour and lustre should be taken into account.
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