Pearls come in a huge range of shapes, sizes and colours. Here we look at how these variations come about to help you find what you’re looking for when buying pearls.

There are a number of factors that effect these changes, primarily the type of mollusk that grows the pearl, but we also need to consider the size of the mollusc, the environment it grows in, the shape of implant used to nucleate the pearls, the location of the implant within the mollusk and of course, the length of time the mollusk has to create the pearl.
Firstly we’re going to give an overview of the different types of pearls; they’re commonly classified as Freshwater, Akoya, Tahitian and South Sea. The nature of the names can be a little confusing as these refer to the type of mollusk, not the geographical location they were grown in. Here’s an overview of each.

Freshwater
Freshwater pearls make up the vast majority of pearls available on the market today; they’re grown in freshwater mussels which are farmed in freshwater lakes, rivers, ponds and streams (i.e. not in the sea) all over the world, but mostly in China. There are different types of freshwater mussels that grow freshwater pearls but the most common is called Hyriopsis cumingi. Freshwater pearls are often non–bead nucleated, this means that they’re cultured using a small piece of another pearl’s soft mantle tissue rather than a bead which is used when culturing other pearl types. We therefore don’t have to worry about nacre thickness and seeing the bead nucleus, as the pearls are all nacre. It also allows for tiny little pearls of less than 1 mm in diameter. Having only reached sizes of around 6mm twenty years ago, freshwater pearls can now grow as large as 11 or 12 mm as a result of improved farming methods. They’re naturally made in a range of lovely pastel colours including pink, white, peach and purple.
A freshwater pearl mussel can grow up to 50 cultured pearls at a time, they’re also a bit more robust than their saltwater cousins (oysters), this accounts for their reasonable price in comparison to saltwater pearls. Freshwater farms initially only produced small rice shaped pearls but through selective breeding of the mussels they’re now producing larger round and near round pearls on a more regular basis.
Freshwater pearl facts:
size: 1-9mm
colour: white, peach, pinky purple
pearls per shell: 30-40
growth period: 2-6 years
common string values: £70-£5,000

 

 

Tahitian
The first thing that hits you when looking at Tahitian pearls is their fantastic colour, they couldn’t be further from what you’d expect, they can also be considerably larger than freshwater or akoya pearls. Their colours are truly remarkable, ranging from black to green to blue to silver and countless shades in between. Tahitian pearls have been growing naturally for millions of years but they only started to be cultured relatively recently. Tahitian pearls are grown throughout French Polynesia, not just in Tahiti, and are made by black lipped, Pinctada margaritifera oysters. As we said, they can be massive, the biggest recorded Tahitian pearl is 26.95mm in diameter and they regularly grow from 8mm-14mm in diameter.
Tahitian pearls are so big because the P. Margaritifera oysters that grow them are huge, regularly reaching 12” in diameter, as well as the fact that after they’ve been harvested the first time the pearls can be reintroduced into a larger, more mature oyster allowing them to be re-covered with nacre and become even bigger. This reintroduction isn’t possible with freshwater or Akoya pearls.
The P. margaritifera is a saltwater oyster, this means that they’re greatly affected by their environment; large, round, blemish free pearls are only found when the oysters live in pristine waters of suitable temperature. Just the slightest increase in temperature, 1-2°C, and the oysters struggle to survive and those that do will produce poor quality nacre. Tahitian pearls are frequently circled, the reason for which is still a mystery to experts but that doesn’t matter because they look beautiful and, as they’re not ‘perfect’, can be bought at a fraction of the cost of circle free pearls.
Tahitian pearl facts:
size: 8-14mm
colour: grey, green, purple, brown, peacock & pistachio
location: grown in French Polynesia, Thailand, Burma, Phillipines, Indonesia
pearls per shell: 1
growth period: 2 years
common string values: £2,000-£20,000

 

 

Akoya
The cultured pearl story began with Japanese akoya pearls in the 1920’s when Kokichi Mikimoto, Tatushei Mise and Tokichi Nishikawa craftily managed to successfully nucleate the saltwater oysters, Pintada fucata, which then went on to produce the first cultured pearls. Akoya pearls have been farmed off the shores of Japan, China and other Far Eastern countries ever since. The saltwater P. fucata is a bit smaller than freshwater mussels and so the farmers can only grow up to five in an oyster at a time (the more pearls in each one, the smaller they will be) and they’re slightly more restricted in size, topping out at around 9mm in diameter, most are 6mm to 7mm.
The akoya is what commonly springs to mind when we imagine pearls, this is probably because they were first to be cultured and so first to market in large volumes. As with their fellow saltwater pearl making oysters, P. fucata are very sensitive to their environment, and Japanese pearl farmers have had to deal with considerable difficulties when reacting to their crops being killed by pollution. This combined with their smaller yield makes them rarer and often more valuable in comparison to freshwater pearls of similar shape, size and quality.
Akoyas are bead rather than mantle nucleated resulting in a far higher proportion of akoya pearls being of round or near round shape. When the water is clean and the temperature’s right, akoya pearls have outstanding nacre and lustre quality. Their natural colours range from white to yellow to a beautiful blue which is still very rare and difficult to find in the UK.
Akoya pearl facts:
size: 3-8mm
colour: white, yellow, grey, blue
location: grown in Japan, South East Asia
pearls per shell: 1-3
growth period: 1-2 years
common string values: £500 to £10,000

 

 

South Sea
South Sea Pearls are grown in exotic locations such as Malaysia, Northern Australia and Indonesia. They’re made by the largest of all pearl growing mollusks, the Pinctada maxima. The P. maxima can produce pearls which are even larger than Tahitian pearls, up to 35mm diameter, although they generally grow to between 10mm and 15mm. There are two varieties P. maxima, silver lipped and gold lipped, with each variety producing pearls in an array of colours close to their namesake. Silver lipped P. maxima make pearls that are white, silver or cream, whereas the gold lipped variety produces an amazing mix of yellow, gold and blue pearls. South Sea pearls have thick nacre which have a unique, satin-like lustre. As with Tahitian and Akoya pearls, South Sea pearl quality is hugely dependent on the environment the oysters live in. They’re sometimes referred to as the canaries of the sea as any rise in temperature or level of pollution will affect the colours produced, shape of the pearl and quality of the surface. If it’s too warm the pearls have poor quality surfaces with blemishes as the oysters making them aren’t as healthy. When the conditions are right, the quality of the pearls are truly outstanding and can be hugely valuable, well matched, high quality pearls have been known to reach millions at auction.
South Sea pearl farmers go to extraordinary lengths to keep the environment in which their oysters live immaculate. They’re devastated when subjected to rising sea water temperatures, pollution and indiscriminate farming methods such as dynamite and cyanide fishing and so spend a fortune protecting the surrounding areas, patrolling them with armed guards to keep them pristine, the happy side effect of which is hugely positive to the environment around them.
South Sea pearl facts:
size: 10-15mm
colour: golden, white, blue
location: grown in Australia, Phillipines, Indonesia, Burma
pearls per shell: 1
growth period: 2 years
common string values: £3,000 to £100,000

 

 

Other pearls to look out for
We’ve given a bit of an overview of the major types of pearls that are available on the market today. There are others such as non-nacreous “pearls” that are made by conchs and melo melo snails but they’re very rare and hugely expensive (A single 16mm melo melo “pearl” recently sold for £50,000 at auction). There are also keshi pearls which are kind of half way in between a natural pearl and a cultured pearl. Keshis are quite rare and beautifully baroque (randomly shaped), they’re made of pure nacre and so highly lustrous. They come about by accident, being made as a result of a rejected bead nucleus or additional irritant that accidentally gets in during the culturing process.

This article is reproduced by kind permission of Jersey Pearl

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