All About Pearls ( Glossary A – C )
A – AAA Grading system
Essence pearls are exceptional pearls, selected for highly metallic lustre, clean surface and shape, in that order. Usually only found by selecting in person. Probably under 1% of pearls will show the mirror metallic lustre we look for.
AAA: The highest-quality pearl, virtually flawless. The surface will have a very high lustre , not necessarily metallic, and at least 95% of the surface of each pearl is free of flaws. Any flaws are very small and hardly noticeable.
AA+ Nearly as good as AAA but perhaps slightly off round when rolled and a few more flaws although these will still only be visible on close inspection.
AA Average to good lustre, off round, blemishing to 20% of surface
A: This is the lowest jewellery-grade pearl, with a lower lustre and/or more than 25% of the surface showing defects. Probably a round pearl will be egg shaped, even from a distance Any website or other seller which talks about
AAAA+++ grade pearls is talking rubbish and this should be queried.
Tahitian pearls have a distinct and separate system, established by GIE Perles de Tahiti, and the Ministere de la Perliculture of Tahiti which grades from A (finest) to D ( poor) but to avoid confusion Miss Joaquim Pearls uses only the A to AAA gradings throughout the website.
Abalone blue pearls
Just being developed in New Zealand. The abalone produces a distinctive and stunningly iridescent blue pearl but is very hard to nucleate as its blood does not clot, so any damage will kill it.
A pearl from the akoya oyster (Pinctada Fucata Martensii). This is a salt water mollusc. Most cultured sea pearls are akoya pearls which are made with a bead nucleus, so that they usually have a good round shape. Big irregularities tend to be tails while less than perfect pearls have nacre with pits or convolutions. Good akoya pearls have a sharply reflective metallic lustre. Smaller (under 8mm) akoya pearls tend to come from China (although chinese production has dropped with the recession) while Japanese akoya pearl farmers are concentrating on producing larger high quality pearls (made-up necklaces marked Made In Japan may have been made with Chinese pearls if under 8mm) akoya pearls are harvested after only 9-16 months.
The problem is in obtaining pearls with sufficient nacre. Pearls with very thin nacre may even ‘blink’ which means that when rolled the nacre blinks to show patches where there is no nacre and you can see the nucleus. Below is a very bad example – the cream colour is nacre and the white is nucleus. Even when the nacre appears solid it can be very thin: peer closely and you can just about make out the thin line of the black nacre on the akoya pearl on the left (which split in half) The nacre on the pearl on the right is so thin the pearl is said to be blinking – if you roll it around it appears to blink, with sight of the nucleus.
Baroque pearls are strictly all non-round pearls but the term is usually applied to pearls which are not round but which nevertheless have a good rounded surface all over. Freshwater pearls are most commonly baroque as freshwater pearls are mantle-tissue nucleated instead of bead nucleated. So round pearls are the exception, although more are being produced as techniques improve. The most valuable baroque pearls are South Sea and Tahitian pearls which are produced by Blacklipped and White-lipped oysters (Pinctada margaritifera, and the Pinctada maxima). Commercial baroque pearls tend to be bigger pearls – there is a balancing act for the pearl farmer between leaving the pearl in the mollusc with the chance of a big round pearl and the likelihood that the pearl will go out of round and become baroque and therefore less valuable
All sea pearls are grown around a bead. It used to be that beads were not used in the production of most freshwater pearls (exceptions include coin pearls for example) However the last couple of years have seen the development of bead nucleation in freshwater pearls, producing second or third graft round pearls of stunning colour, lustre and shape. High quality bead nuked pearls are still exceptional and unusual and therefore very expensive, but can be up to 14mm. These freshwater pearls have been bead nucleated, and you can see the thick layer of nacre surrounding the nucleus
Or sometimes biwi-A freshwater pearl grown in lake Biwi in Japan. Not in the present as the pearl farms were closed due to pollution. Now often applied to any stick pearl
White pearls are colour treated by bleaching. This applies to both Akoya and Freshwater pearls. Black-lipped Oyster Pinctada margaritifera This oyster produces the Tahitian black pearl
Term to describe poor quality bead nucleated pearls where the nacre does not even fully cover the nucleus. When the strand is rolled the pearls look as if they are blinking.
A pearl that is attached to the inner surface of a mollusc shell
Often rounded on one side and flat on the other. Sometimes also called a fastener pearl . Most often used to make stud earrings, because in larger sizes round pearls can be too proud of the earlobe.
Classic term to identify the amount of gold in metal. Different metals are added to gold to harden it and make it more durable. Expressed as a fraction of 24 parts so that 24ct is fine gold or pure gold, down to the lowest standard which is 9ct in the UK, usually 14ct elsewhere.
No one knows exactly why some pearls develop circles. These can be bands of colour or grooves, as if the pearl has gently spun on its axis in the pearl sac. While circle pearls tend not to be the most expensive they are not as yet imitated and have stunning variety
Natural freshwater pearls tend to be shades of white through to pale pinks and peaches and golds The intensity of the colour depends on the species and strain of host mollusc plus the farm water and food. Tahitian and South sea pearls are not usually dyed.
Many pearls are coloured treated as part of the processing between farm and retailer. There is however, now a trend towards completely natural colour untreated pearls. Silver nitrate and gamma radiation are two treatments. (see separate entries) and white bleached akoya pearls are often ‘pinked’ – delicate tinted to a faint pink overtone which softens the colour and is supposedly more flattering and desirable.
Usually a round flat pearl shaped like a coin, also used to describe fancy hearts, squares, lozenge and other shaped pearls
Rarest of the natural pearls, conch pearls look a bit like jelly beans. They are not nacreous but have a distinctive flame pattern on the surface. The colours range from orange, through yellow to pink
Cook Island Pearls
Specific group of south sea islands which produce their own distinctive pearls from Pinctada Margaritifera. The pearls show the same colours as Tahitian pearls but are softer looking in shades
Very rare pearls produced by one farm in the Sea of Cortez, Mexico,from Concha Nácar, Pteria sterna, the rainbow lipped oyster. These pearls fluoresce red under UV light.
Cross can be diagonal or crucifix. Some cross pearls which also have nacre between the limbs have been sold as butterfly pearls
The cockscomb pearl mussel was the mollusc originally used by the Chinese when they started to culture freshwater pearls. The pearls produced are known as rice crispie pearls because of their resemblance to the cereal
A pearl formed after a human puts a bead nucleus or mantle tissue into a mollusc. Any farmed pearl is cultured. Any real pearl feels faintly gritty when rubbed gently on your teeth and the drill hole tends to be very small (usually 0.7mm)(because pearls are still often sold by weight)
Culturing Freshwater Pearls
In freshwater mussels, insertion of only mantle tissue is enough to trigger the making of a pearl sac and therefore pearl production. It used to be that beads were not used. However the last couple of years have seen the development of bead nucleation in freshwater pearls, producing second or third graft round pearls of stunning colour, lustre and shape. High quality bead nuked pearls are still exceptional and unusual and therefore very expensive, but can be up to 14mm. Even larger pearls are being produced with pearls nucleated with a lump of mud (!) these pearls, third graft, are of stunning lustre and a rather keishi appearance so far. When drilled the mud is drained away so that
the pearl is hollow and light in weight. However most freshwater cultured pearls are still solid pearl nacre, even pearls up to 15mm. This means that they are arguably more durable but the chances of non-perfect round shapes are higher
Since so many good quality white fake pearls are now available the trend is for natural colour pearls to remain untreated. Usually white freshwater pearls have to be bleached. There are many natural colours of freshwater pearls; pink, peach, purple, yellow, white, grey, brown, champagne and black. Only freshwater pearls are ever pink, peach and purple.. Black pearls are created by black oysters. The darker the colour is, the more valuable the pearl and black pearls with a little bit of green are the most precious.
Other colours are created artificially by dyeing or irradiating the pearls, or treating chemically. It is quite hard to tell with some colours whether or not a pearl has been treated (although a deep blue or hot pink pearl is never natural). Irradiated pearls are often silver/grey, blue, green, or gold to brown. Most dyed pearls are colourfast, and irradiated pearls won’t lose their colour, and are not radioactive.
While Salt water oysters will only manage to make one pearl each (which keeps up their scarcity and value) freshwater mussels are more obliging and will make 20 or more each. Some farms are developing their own strains of mussel, selecting for quality, while other farms will buy in their mussels ready nucleated. This careful breeding is producing more strongly coloured natural colour pearls. After harvest in China pearls go from individual farms to pearl factories where they are bleached to be white pearls, or otherwise coloured or processed, drilled and sorted, and assembled into strands.
Culturing Saltwater Pearls
Several distinct types of pearls grow in salt waters. Farming methods are pretty much the same for all of them
The process of growing sea pearls in oysters was discovered (or re-discovered as there are arguments about this) by Mikimoto in 1893. All pearls which grow in salt water start with baby oysters which are either artificially bred in a
hatchery or spawn naturally then are collected by placing various lures in the water to attract the spats as they are called. The baby oysters are grown on for two or more years until they are big enough to manage to accept a grafted bead nucleus.
With all sea pearls the pearl is grown around a nucleus – a starter bead plus a tiny fragment of mantle tissue which grows to form a pearl sac around the bead. As the mantle tissue is tissue for making nacre/shell it carries on doing this, secreting nacre on the inside of the sac and onto the bead. Mantle tissue makes the pearl sac because its job normally is to secrete the mother of pearl to make the smooth and lustrous lining of the oyster’s shell.
Early in the morning of the day an oyster will receive a nucleus, it is taken out of the water and then left for about half an hour, by which time it should have opened its shell a little. The shells are wedged open. Any unopen shells go back into the water to be left for another attempt in a few days Nucleating oysters is a skilled task – even opening the shell too far can kill the delicate creature. The bead-plus-mantle tissue scrap is inserted into an incision into the body of the oyster, either at its gonad or by the connective tissue. Remarkably having a bead stuck into its sex organ seems to make the oyster more active sexually rather than less!
A nucleus is a (usually) round bead made from shell and cut and polished into a smooth round -usually about 8mm in diameter for first grafting The oyster is secured in a clamping device in front of the operator and either the wooden wedge is left in place or a retractor which allows the shells to be forced further apart is inserted. If the oyster is opened too far it will die. The aim is for this process to take under a minute and it is reckoned that it takes a month at least for the oyster to recover.
The actual process is that the grafter, working through the tiny opening between the two halves of the shell, makes n incision of about a centimeter into the oyster’s gonad or into its connective tissue then places the mantle tissue and nucleus (dipped in water and held by a suction tool) into this slit. The two insertions must be touching, or a pearl sac will not form. Then the oyster is put back into the sea. There are various ways it is held but they all work to allow the oyster to feed happily and grow. No-one knows exactly why some grafts become great pearls and others don’t. It is probably a mixture and combination of genetics, grafting skill, and growing conditions. Many farms keep a record to see who is the best grafter (!)
The implanted tissue forms a pearl sac around the nucleus and starts to secrete nacre. It will take between two and four years for the pearls to form. The tissue implant is only about 1mm square. It will form the pearl, which has no genetic relationship with the host mollusc. Nacre is mostly carbonated calcium. As long as the irritant is present the mollusc continues to add layers of nacre until a smooth lustrous pearl is formed.
Only one pearl per oyster can be produced. Sometimes oysters can be re-nucleated after harvesting to produce a bigger pearl with a bigger nucleating bead, or, if no bead is used a keishi pearl can be produced (think of the inside of an inflated then deflated balloon) Oysters are fairly fussy about their conditions and if forced to open too much they will die, as they will if they are out of the water too long, get too hot or too cold, if the water in which they live becomes too saline or not saline enough (this happens when a river floods and any oysters living in the estuary may well die because of the temporary dilution of salinity. It takes about 18 months to two years to grow tahitian and south sea pearls. Tahitian pearls are required by local law to be x-rayed and have a minimum nacre depth of 0.8mm all round. South sea pearls tend to have much thicker nacre than this.
There is some controversy about how long akoya pearls need to stay in the water. Some are harvested after only six months but these pearls can have gaps in their nacre so the bead is visible (they are said to ‘blink’ when rolled) and they will wear out quickly. But they will, of course, be very much cheaper. The pearls are cosseted. They will be cleaned several times to remove algae, vegetable growths and barnacles, and the farmer must keep an eye on the weather conditions – some akoya farms now monitor temperature and salinity and move the oysters if conditions are not ideal.
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