By Lauriane Lognay

The pearl is among the oldest known gems of our world (not the absolute oldest, but humanity has certainly known the pearl longer than our dear old zircon). The earliest mention of them is around 4000 BC, with the Persian Gulf considered one of the most ancient sites.

Historically, pearls have been considered divine gifts, rich with love and royalty. Kings and crowns harboured natural pearls as a sign of power, purity, and wealth—almost as though the gems would bring prosperity and long life to those who possessed them.

Meanwhile, in the New World, these beauties, which are largely comprised of calcium carbonate (CaCO₃), were considered to be the most precious and expensive export (this was before the development of different mines in Mexico and Peru for gold and silver). Indeed, their value exceeded that all of all exports, such as spices.

Early, pearly days

The first notable sources of pearls were in the Gulf of Mannar, located between the west coast of Sri Lanka and the southeastern tip of India, and the Persian Gulf. In the centuries to follow, sites began to pop up around Panama and Venezuela, with written proof of findings noted around the 15^th century by Christopher Colombus and Vasco de Balboa. Unfortunately, due to overfishing, these sites are, for the most part, no longer viable pearl sites.

In modern jewellery, cultured pearls are commonly used in place of their natural counterparts (with a few exceptions, such as conch pearls, which are still used in high-jewellery pieces). Cultured pearls have nearly the same composition as natural ones and, thanks to advances in technology and thorough research on pearls’ growth, these gems offer a wider variety of colours and shapes than ever before.

Pearls, unlike gemstones, are rarely touched by humans; their beauty and softness makes them one of the few things humans simply leave alone and opt to put in jewellery in a natural state. This has been true since ancient times. Today, the round wonders can be dyed, shaped with new types of nucleus, and even sometimes faceted, but the grand majority of them remain untouched.

Pearls are vastly sensitive creatures; you will often hear dealers refer to them as ‘alive’ or ‘dead’ depending on their state, as growing and caring for them is tricky business. It’s not uncommon for farms to use classical music to open the mollusks, so as not to stress them out. Other farmers insist on complete silence, while others still sing and play instruments—to each their own, I suppose.

Sharks, sand, natural pearls, and heaven

When describing natural pearls, some poets refer to them as tears of the gods that have fallen from heaven, while others still regard them as a piece of the moon that ended up in the ocean. Indeed, when it comes to these beautiful gems, there are countless stories of kings and queen speaking of divine gifts.

Reality, of course, is a bit different. Some natural pearls were simply formed from a grain of sand that ended up in the mollusk and irritated it, causing the phylum to activate its defence mechanism and secrete the nacre to envelop the intruder.

In gemmological studies, there are also cases where sharks create natural pearls, as their excrement in the ocean causes some live parasites, developed in dung, to enter mollusks and irritate them. They then die in the mollusk’s ‘body,’ all while being circled in countless layers of nacre.

Thankfully, today’s cultivated world means we no longer need shark poo to create the calcium and aragonite beauties we know as pearls—likewise, we also don’t need the tears of gods.

How to calculate value

When it comes to determining a pearl’s value and durability on the market, there are many factors to consider.

Lustre

A pearl’s lustre refers to the way light reflects on its surface and back at you, representing the gem’s brilliance—the higher its lustre, the more valuable the pearl. A high lustre is the sharp contrast in colour on the pearl, from the dark saturated colour of the pearl to the whitish appearance of a high lustre on its surface.

Pearls of low-quality lustre do not shine much and appear chalky or milky white on the surface. Of course, the pearl’s surface quality also contributes to its lustre. If the surface is too full of imperfection, the lustre won’t have a chance to show its full potential. The same can be said for the thickness of the nacre on the pearl.

Nacre

The quality and thickness of the nacre on a pearl are imperative when judging its value. The nacre is the result of the mollusk (often oysters or mussels) secreting a substance to combat intruders in their shells, which results in the formation of pearls. (A significant percentage of pearls formed are not considered saleable, which is why the round treasures have always had a certain value throughout history.)

Until as recently as a few years ago, Tahitian pearls had to follow a strict code for nacre thickness in order to be sold or exported out of the country. Although this is no longer the case, generally speaking, the thicker the nacre is, the better the pearl.

While saltwater pearls have a nucleus, freshwater wonders often don’t require cores to form. This often results in thick coats and a longer gestation period as compared to other types of pearls.

The durability of a pearl is directly related to the thickness of its coat—if it’s too thin, it will crack or be brittle. Uneven distribution can cause some ‘dead zones’ on the surface where it doesn’t shine and instead is milky and/or matte.

Colour

When it comes to a pearl’s value, uniformity in colour is important, and is often a major factor in determining its value on the market. A pearl may have high lustre and no blemishes on its surface, but if it’s not pleasing to look at, it won’t be expensive. What we’re looking for are deep saturated colours. A light, yellowish white, for example, will not be as pleasing to a client as a deep golden (untreated) pearl, or a white pearl with pink overtones.

When considering a pearl’s colour, you will notice three things:

1. The main colour of the pearl (the ‘body colour’)
2. The iridescence or orient (akin to a rainbow of colours that travel and change as you move the pearl)
3. The overtone (the colour tone overlaying the main colour of the gem)

For example, you can have a black Tahitian pearl with green overtones and some iridescence on it, or a ‘purple’ Tahitian pearl (a black pearl with purple overtone). Pearls can be many different colours, including pistachio, pink, purple, yellow, green, and even blue in some rare occasions. Regardless, the more vivid the body colour and overtone, the more valuable the pearl. Iridescence is a great bonus.

Shape

Cultured pearls come in a variety of shapes, the main of which are:

• round;
• half-round;
• button;
• baroque;
• keshi;
• pear;
• egg;
• circled; and
• rice-shaped.

You can also find some stars, moons, and even crosses. Thanks to new techniques developed after years of research, today’s pearls can have shaped nuclei (or cores), which allow them to grow in specific forms.

Nonetheless, the most valued shape for a pearl remains the perfect round. This shape is the hardest to obtain, which makes it the most expensive (and, generally, the most sought-after).

Baroque pearls, depending on their shape and size, can be quite desirable and valuable, too. Some artists use them in jewellery, and are able to transform the stone into an animal, object, or even a person. When imagination is applied, the general shape of the baroque pearl can resemble an elephant, a mermaid tail, or even the beginnings of a palace—that’s where the jeweller comes in to complete what would be a masterpiece with a uniquely shaped pearl.

Origin

Some countries where cultured and natural pearls can be found include Indonesia, Vietnam, Tahiti, Japan, China, Philippines, United Arab Emirates, Myanmar, Australia, Micronesia, Fiji, French Polynesia, Germany, Russia, Scotland, New Zealand, and Mexico. Anywhere in the world you can find cephalopod, shells, oysters, or mussels, there is a slim chance pearls can be found there as well.

Surface quality

The less imperfection a pearl has on its surface, the more valuable it will be. These imperfections can range from undesired line formations within the pearl, small dots (or ‘spotting’) on its surface, protrusions, or dents. Other times, there are sections on the pearl where there is not enough nacre and discolouration is visible. Some also consider surface irregularity to be an imperfection in the pearl (scratches and cracks also enter in this category).

As a rule of thumb, anything that can be observed either inside a pearl or on its surface without employing a loupe will impact its price. Unlike other gems where imperfections can help identify a stone or even enhance its beauty, pearls need to be as perfect as nature can make them to achieve their best value.

That said, some pearls with small imperfections and/or bumps are likely to be more accepted when incorporated into a piece of jewellery with stones of similar appearance. Likewise, if you have some big, single pearls with small imperfections, a good way to sell the perceived flaw is to call it ‘the personality’ of the gem. After all, if the blemish or welt is miniscule and doesn’t compromise the durability of the pearl, than the quality just makes it more unique for the customer. Some of today’s shoppers even like it when bumps and welts are evenly distributed throughout the pearl.

Size

As a general rule, the bigger the pearl, the more expensive it will be. Depending on availability, sizable pearls are not easy to obtain in a cultured environment, and this is even more challenging in nature.

Treatment

Predictably, any treated pearl is less valuable than its untreated counterpart. These days, pearls can be dyed, irradiated, bleached, buffed, coated, filled (with epoxy), silver-salted, heated, and injected with metal fluids. Some of these treatments can be seen directly; others are only apparent once the pearl is pierced; and others still have to be tested in a lab. Indeed, treatments are becoming more difficult to detect as these techniques become perfected and practiced. As such, visiting a local gemmologist or sending an expensive pearl to a reputable lab to ensure it hasn’t been treated is a safe way to buy. An authentic pistachio-coloured, Tahitian pearl would be up to 10 times as valuable when compared to a dyed or treated one, for example.

Matching

‘Matching’ refers to strands or pairs of pearls; not standalone stones. The more pearls you have in your possession that are of similar lustre, shape, colour, size, etc., the most valuable they will be.

A whole strand of vivid yellow South Sea round pearls with no surface imperfection, for example, would be far more expensive as a whole than any standalone pearl of this type. Matching, however, does not always refer to the same colour; sometimes (particularly in cases of Tahitians), pearls are matched by their lustre, body colour, and colour intensity, but have a rainbow of different overtones and orient. Such strands are as difficult to harmonize as any white pearl strand.

Pearl types

Alongside natural pearls, cultured varieties can be divided into two main groups: saltwater (from oysters) and freshwater (from mussels).

For saltwater pearls, common types include akoyas, South Sea pearls, blue pearls, blisters (including mabe pearls), rainbow pearls, akoya keshi, and black Tahitian pearls.

Meanwhile, freshwater varieties include Biwa pearls, Kasumiga pearls, and keshi (or ‘reborn’).

Finally, natural pearls are comprised of blisters, seed pearls (or keshi), abalone, scallop pearls, conch pearls, melo pearls, and quahog pearls.

Some standalones

‘Mother-of-pearl,’ known as the interior shell of a mollusk, is often carved into cabochons, small sculptures, and more. It is considered less expensive than pearls in general.

Meanwhile, abalone is, in reality, from a snail. Though not from any oyster or mussel, the powerful iridescent nacre it sometimes produces is typically enough for it to be considered a ‘pearl.’

And, of course, let’s not forget the lesser known pearls out there, which are just waiting to be brought to the jewellery world, including the non-nacreous natural ones (such as Hexaplex Erythrostomus; jellybean pearls from Queen conch shells; Horse conch [Triplofusus giganteus, the melo snail pearl], porcelain pearls from different clam species, Spondylus pearls, nautilus pearls [from a cephalopod], and so on), and the nacreous ones (such as turbo pearls, Oriental pearls [natural pearls found in the Persian Gulf], and pipi pearls from Cook Island).

Conclusions

The pearl universe is ever-expanding, and describing the shells, mollusks, and even snails that can produce pearls and how this is achieved could easily fill a 500-page book. That said, I do hope you’ve learned a few things about these ancient treasures. 

Lauriane Lognay is a fellow of the Gemmological Association of Great Britain (FGA), and has won several awards. She is a gemstone dealer working with jewellers to help them decide on the best stones for their designs. Lognay is the owner of Rippana Inc., a Montréal-based company working internationally in coloured gemstone, lapidary, and jewellery services. She can be reached via email by contacting rippanainfo@gmail.com.

References

• CIBJO Pearl Book (2015) by Shigeru Akamatsu
• Pearl Buying Guide: How to Identify and Evaluate Pearls & Pearl Jewelry, 6^th edition (2017) by Renée Newman, GG
• The Gemmological Association of Great Britain (Gem-A) Diploma, Fellow of the Gemmological Association (FGA) notes on pearls
• “Sustainable Pearls,” found online at
  www.sustainablepearls.org.