Pearls - Natural, Cultured, Freshwater: What is the difference?
A natural pearl is created when an irritant or parasite gets inside a mollusk, such as an oyster. As the oyster finds this irritant uncomfortable, it creates a smooth barrier around the substance called nacre. Over years, the layers of nacre build up to cover the irritant completely and a pearl is created.
Natural pearls like this are very rare and therefore extremely expensive to purchase.
Pearl farmers insert irritants deliberately into the oysters to force them to produce pearls through a process known as "seeding". Cultured pearls are real pearls that were not formed through an accident of nature.
As the name implies, Freshwater Pearls are farmed in freshwater lakes. They are developed inside a mussel rather than an oyster. All mollusks create nacre which forms the pearl.
Pearl farmers may create up to 25 pearls on both sides of the mussel shell, resulting in a potential harvest from one mussel of up to 50 pearls. Many tons of freshwater pearls are produced each year. China is now the only commercial producer of freshwater pearls.
A strip of tissue is cut into 3mm squares which are then inserted into the mussel. When inserting, the technicians will often give the tissue a small twist which is believed to create a higher number of round pearls.
As the nacre slowly builds up around the inserted tissue, the tissue eventually degrades and over time the pearl structure becomes solid nacre - similar to a natural pearl. This formation also means that freshwater pearls are very tough and durable - much more so that some other pearl types. Pearls usually take between 2 and 3 years to grow.
Freshwater pearls are favoured by jewellery designers because they are abundant, good quality and much cheaper to purchase than saltwater pearls.
The quality of freshwater pearls is based on a grading system of a series of "A" values, based on luster, shape, surface defects, colour and matching.
Freshwater pearls typically range from 3 to 12mm. Very large sizes have recently become available using a special technique. These pearls are referred to as "Edison" pearls and are usually between 15 and 16mm.
Very few freshwater pearls result in a perfectly round pearl. The more round the pearl, generally the more expensive it is.
Near round or off-round pearls are more common and offer excellent value for money. These pearls still appear "round" to the naked eye.
Pearls which have an irregular, non-spherical shape are referred to as "Baroque" pearls. They are often lumpy, curved and free formed. They are becoming increasingly popular as each one is unique, they are interesting to look at and they have a more "natural" look to them.
Baroque pearls are the most common pearl shape and account for around 40% of the pearl harvest each year.
Button pearls are usually round in shape
when viewed from above, but from the side are flatter on one side and domed on the other. They are ideal for making stud earrings as they sit closer to the ear than round pearls.
The button shape is created as the
mollusk inside the shell tries to rid itself of the irritant. Tt tends to build up more nacre around the area where it is in contact with its flesh and no so much on the side
which faces the shell. Therefore the pearl which is created is flatter on the side facing the shell and rounded near the flesh of the mollusk. This is one of the most common shapes of freshwater pearls.
Freshwater pearls can come in a wide range of colours including; pink, peach, lavender, grey, white and black.