Imagine you are eating at a fashionable restaurant in the 1950s. You have ordered a plate of fresh oysters, and your wife is very excited. She always hopes that one of the oysters will contain a pearl. It doesn’t seem to matter how often you explain that eating oysters don’t contain pearls, she always gets her hope up. Imagine your surprise though when you see that one of the oysters has indeed been growing something which resembles a basic pearl. It is not round, or indeed something which could be used in jewellery, but it is fascinating none the less.
When I showed the children this oyster shell they were intrigued and surprised by it. Many of the children were aware, because of past discussions, that eating oysters are not the sort from which pearls are harvested, and assumed that eating oysters did not have the ability to grow pearls of any sort. They were amazed to see the start of ‘something which looks sort of pearly’ growing in this ordinary oyster, and became rather hopeful that one day they really would be able to find a pearl!
Pearls are an amazing thing, unlike any other precious materials like metals and stones. They don’t have to be cut, polished, shaped or worked - pearls are grown by oysters and when they are harvested they are, essentially, ready to wear. So how are pearls created? Essentially, a foreign object of some sort becomes stuck inside the shell and becomes an irritant which the soft oyster cannot get rid of. They have to do something to protect themselves from the irritant, which could be anything from a parasite to a tiny piece of shell. As a defence, the oyster begins to cover the irritating object with a substance called nacre. This substance is hard but smooth and over time layer upon layer of nacre will build up over and around the irritant. This makes the irritant, in essence, disappear and what is left behind is a pearl.
Making a pearl is a natural process, and in fact, almost all living shelled molluscs are able to make them. This includes not only oysters, but also mussels and even snails! However, not all pearls are created equal. Although many different molluscs can make pearls, a lot of these do not have the lustre or iridescence which is so attractive in a pearl and many are also too fragile to be used in jewellery etc. These pearls have little to no value, and can be found in edible mussels, oysters, escargot snails and other edible molluscs. The oyster shell which I showed the children, which comes from a Sydney Rock Oyster, is an excellent example of such pearls. The most valuable and sought after pearls come from species which are not eaten at all, but are cultivated specifically for their ability to make beautiful pearls in various colours (ranging from the well known white to black and even red!)