Those lucky enough to be born in June can claim pearls as their official birthstone. Here, Gem-A gemmology tutor Lily Faber FGA DGA EG, looks into the history and nature of these treasures from the sea.
When thinking of pearls, one conjures up images of perfectly round, white gems with a subtle iridescence. Pearls, in fact, come in many colours from white to pink to grey to blue to green, with varying colours of iridescence like pink and green, and can form naturally or can be cultured.
Most pearls that are sold on the market today have been conjured into existence with the aid of human hands.
Cultured pearls have dominated the pearl market since the early 20th century, ever since Kokichi Mikimoto began to mass-produce, successfully market and sell them.
The History of Pearls
Going back in history, natural pearls were once so coveted that in 55 B.C., Julius Caesar attempted to invade Britain for its copious supplies of river pearls (he did not succeed!).
Pearls were seen not only as a symbol of wealth and exclusivity, but also of purity, integrity and wisdom. In ancient Japan, it was believed that pearls were formed from the tears of mythical creatures such as angels and mermaids. Often worn by 17th, 18th and 19th century European aristocracy both in daily life and in painted portraits, a strand of pearls represented unimaginable wealth.
Pearls photographed by Gem-A's Pat Daly.
Prior to a crash in pearl prices in 1930 and the predominance of cultured pearls, good quality natural pearls were highly valued and exceedingly rare.
They were so sought after, in fact, that in 1917, a double strand of 128 natural, graduated pearls, was traded by the jewellery house Cartier for a large mansion on 5th Avenue in Manhattan, New York (still their flagship store in the US), owned by American industrialist Morton Plant.
The necklace, given to Plant’s wife Maisie, was worth just over £1 million at the time, but when it was sold 40 years later, it made a mere £100,000. To compare, the building today is worth millions of pounds.
Formation and Shapes
Contrary to popular belief, pearls are not formed when a single grain of sand irritates an oyster’s flesh, as it would simply eject the sand.
Instead, a parasite or tiny irritant that invades the mantle causes the oyster to cover it with successive layers of nacre, or mother-of-pearl, which is a combination of calcium carbonate in the form of aragonite platelets, and conchiolin. Saltwater oysters and freshwater mussels form these natural wonders with their pearly lustre. Conch and melo snails can also create a marine pearl, without the iridescence known as a pearl’s orient.
When cultured, pearls are formed with a bead nucleus (nucleated cultured pearls) or without one (non-nucleated cultured pearl). It is not always easy to recognize whether a pearl has a bead nucleus, but one test that can be used is known as candling.
Cultured Akoya Pearls photographed by Pat Daly.
Shine a strong light through the pearl, and you should see the bead in the centre, surrounded by concentric rings of nacre. You may also be able to see the delineation between the bead and the outer nacre layer if looking down the drill hole of a bead with a 10x loupe.
It is considerably more difficult to recognize if a pearl is natural versus non-nucleated, and you will need to send it to a lab for further, advanced testing such as an x-ray.
Pearls can come in any shape or form. The most coveted shape is round, however, they can be off-round, oval, flattened, an indefinable shape only known as baroque, or anything else you can imagine. Beaded cultured pearls with take the shape of the nucleus. In fifth century China, they were using small Buddha medallions for their nuclei.
Care and Caution
Pearls are an extremely soft gem material and are susceptible to damage. They have a hardness of 3.5 to 4 on the Mohs’ scale, which, compared with gemstones like sapphires, is relatively very soft.
Pearls also have a small percentage of water in their structure and they can crack or craze as a result of heating or dehydration. Pearls can chip and fracture in addition to being easily scratched by other jewellery and even each other, resulting in a powdery-looking surface.
The calcium in their composition can easily be attacked and damaged when put into contact with chemicals of varying acidity from soaps, detergents, perfume and even your skin.
Abalone Pearls photographed by Gem-A's Pat Daly.
The rule of thumb, when wearing pearls is to keep them high, in earrings or necklaces, and they should be the last things you put on and the first things you remove at the end of the day.
While pearls are beautiful, they are not meant to for daily wear, especially not in jewellery like an engagement ring due to their fragile nature. Wash only with warm water and dry with a soft cloth.
Pearls can be a beautiful addition to your jewellery box, particularly if you were born in June. Ensure that you care for them properly and they will be a source of joy for years to come.
Interested in finding out more about gemmology? Sign-up to one of Gem-A's courses or workshops.
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Cover image: Pearls photographed by Gem-A's Pat Daly.
Featured in the Spring 2018 issue of Gems&Jewellery, Rui Galopim de Carvalho FGA DGA explores how ‘alternative facts’ have resulted in an informal nomenclature that permeates the world of gemmology. Here, he offers some examples of these long-standing quirks in terminology.
From the the Spring 2018 issue of Gems&Jewellery, here Harold Killingback FGA explores chatoyancy in sillimanite cabochons, an optical phenomenon where a band of light, known as a 'cat's eye', appears to hover above the surface of a stone, resulting in a striking lustre and colour.
Every year Gem-A gives its members and students the chance to show off their skills with the camera through the Gemstone Photographer of the Year competition. Have you got what it takes to be Gem-A's best photographer of 2018? Entries are open now and close on August 31, 2018.