Pearls are organic gems and are given to us by nature, with a perfection and beauty upon which man cannot improve.
Pearls are classified as Natural or Cultured. Until Kokichi Mikimoto created cultured pearls, all pearls were natural. Nowadays, over 95% of the world pearl production is cultured.
A pearl’s structure comprises mostly CaCO3 calcium carbonate and a little water.
Natural pearls can be further divided into saltwater pearls (gulfs, bays, seas, oceans) and freshwater pearls (rivers, lakes etc.), although these are mostly saltwater.
The mollusc secretes layers of nacre (pronounced “NAY-KER”) around an irritant (which becomes the nucleus) to protect itself. This irritant enters the mollusc by an act of nature. Most people describe the irritant as a grain of sand, but it can be many things such as very little animals, snails, worms, particles of seabed debris, shell bits, clay, but not usually sand as is so often thought.
Natural pearls are much rarer nowadays and very expensive, mainly due to the many pearl farmers who have turned their attention to cultured pearls.
Cultured pearls can also be further divided into saltwater and freshwater varieties, and account for over 95% of world production.
Both freshwater and seawater cultured pearls are hugely popular. Typically, saltwater pearls are rounder and more expensive than freshwater pearls but the freshwater pearls are cultured in a huge variety of shapes and colours, adding more interest and versatility.
With cultured pearls, man has introduced an irritant into an oyster or mussel and then ‘cared for it’ until the pearl or pearls are ready to be harvested (removed from the shell).
For freshwater pearls, the irritant/nucleus is usually a piece of shaped mantle (mollusc tissue that secretes nacre) from another mollusc. The shape of the inserted mantle tissue determines to some extent the final shape of the pearl. However, it is the mollusc that makes the final shaping decision and man cannot change that! Freshwater pearls are grown in mussels, each of which can grow between 10 to 20 pearls. That is one main reason why freshwater pearls are relatively inexpensive.
For saltwater pearls, the irritant is usually a shell bead nucleus as well as a piece of mantle tissue. One of the most widely used shell beads comes from the American freshwater mussel shell. Saltwater oysters tend to die either when the nucleus is inserted (result – no pearl) or when the pearl is harvested. Oysters only grow one pearl at a time and with only one oyster in five providing a saleable pearl, this accounts for the higher price tag. However, Japanese seawater pearls tend to be more expensive than Chinese seawater pearls mainly due to the higher labour cost and the higher quality produced.
In both cases, the shape and size of the irritant, as well the length of time in the shell, will, to a greater extent, determine the shape and size of the pearl.
Imitation pearls are not grown in an oyster/mussel or living creature host and therefore are not considered as pearls.
Perliculture is the art of growing the pearl, much as viticulture and viniculture refer to the arts of wine-making.
The cultivation period of pearls typically ranges from six months to five years.
- Freshwater pearls have fairly long culturing periods (2-5 years) as they are all nacre.
- Saltwater pearls are sometimes cultured for only 6 months; this results in a thin nacre which will not last a lifetime but can be sold more cheaply due to the shorter investment.