While most of the world’s jewellery is fashioned from gemstones and precious metals mined from the earth, there is one special exception that is created by a living creature- the iridescent and mysterious pearl! Pearls are formed by a biological process inside the craggy shells of oysters.
To understand how the precious natural spheres that Pearl Jewellers in Australia use to create such beautiful necklaces, earrings, and bracelets are formed, we must first understand the workings of the oyster’s unique anatomy!
The oyster is a type of mollusc, a cousin to muscles and clams, and like them it is a bivalve, meaning that its shell is composed of two halves, which are called valves. The oyster shell’s valves are held together and sealed by a strong elastic ligament, which can be quite difficult to open, a process that usually requires an oyster knife! This ligament keeps the valves open when it is submerged so the oyster can feed on tiny organisms floating in the water.
As oysters grow larger, their shells must also grow by adding new material to the edges of its shell produced by the mantle, a thin tissue layer lining the shell’s interior. The mantle’s glands extract minerals from the water and convert them into its hard shell, which is mostly composed of calcium carbonate.
The oyster’s shell has three layers. The innermost, is known as the nacre layer, lines the inside of the shell and is called “mother of pearl” thanks its shiny, iridescent, appearance, and is used to make buttons and other ornaments. This nacre layer also forms the pearls!
So, how exactly are pearls formed inside an oyster? The process begins when a foreign substance accidentally enters the oyster, irritating the mantle much like a splinter irritates our skin! The oyster’s natural reaction is to protect its soft insides by covering that irritant with layers of the same nacre substance that creates the shell, continuing until concentric layers of nacre form a pearl. Nacre can also be used as an ingredient in women’s perfumes!
There is a common misconception that pearls are formed by a grain of sand entering the oyster, but this has recently been discovered to be wrong. Technically, it is possible for a grain of sand to reach the centre of a pearl, but the species of oyster that produce pearls live on sandy ocean or freshwater floors and can easily expel sand and other miniscule objects like tiny bits of seashells.
As it turns out, most natural pearls are formed in oysters in response to a parasitic intruder like a drill worm that burrows through the oyster’s hard shell and triggers the mantle to secrete a protective barrier around the nasty little invader! So, the pearl that results is usually really a parasite covered over and smothered in layers of nacre, an ugly centre to such a lovely result!
Most natural pearls can be found in a size range of just 1 millimetre to an average of 7 millimetres. A pearl that grows to a size of 10 millimetres is rare, and the larger the natural pearl is the greater its price!
