One of the oldest prized gems is the pearl. What most people don’t realise is that every bivalve mollusc has the ability to produce a pearl. It is nature’s way of covering an irritant so that the creature can live more comfortably. Of all the molluscs only a handful produce a pearl that has the lustre and orient of pearl to be considered gem quality.

These are the South Sea oyster Pinctada Maxima, (produces the white and golden colours) The Akoya oyster Pinctada Fucata, (produces the white and rarely the grey), the Pinctada Margaritifera, known as the black lip oyster that produces the queen of the sea; the black South Sea pearl. Also fresh water mussels produces pearls (white and often dyed to a variety of colours).

I am Australia’s representative on the World Jewellery Congress (CIBJO) commission for looking into creating the pearl classification system. This will be based on the 5S system.

The 5S (size, shape, sheen, surface and source) is what we experts use to distinguish not only the origin of the pearl but its quality and value. This criteria is used for both the natural and cultured pearl. In recent years the double culturing process used on the freshwater pearl has made them as round as its saltwater counterpart, however the lustre of the Akoya and south seas pearls are still superior.

In the pearl world, the natural pearl is the most sought after. This pearl has been produced with the interference by man. All other forms of pearls produced are called cultured pearls. That is where a bead is placed into the oyster or mussel to stimulate pearl production.

Due to the size of the south sea oyster compared to the Akoya oyster pearls produced by south seas oysters are much larger than their Akoya counterpart. The average size of the cultured south seas pearl is 12mm.-14mm. ø whilst the Akoya cultured pearl average from 4mm.-8mm. ø. Fresh water pearls have a variety of shapes from very irregular called rice pearls to round. They can range from an average of 3mm -10mm. ø.

It must be noted that there are other kinds of sort after pearls including the rare pink conch pearl, the abalone pearl and the paua shell pearl from New Zealand known as the Empress pearl. 

- Ronnie Bauer