Most people when they imagine a pearl are picturing perfectly round, smooth spheres, with an iridescent creamy white appearance. The reality is that pearls are usually irregular in shape, each one is different and to find one that is completely round is almost unheard of, not to mention trying to make a whole necklace of pearls that are all more or less the same. Natural pearls are the rarest and most highly valued variety, but nowadays most pearl jewellery is made from cultured or farmed pearls, which are grown on pearl farms across the world by inserting a bead nucleus inside an oyster or mussel shell to encourage the formation of a pearl.
Aside from whether a pearl has formed naturally or been farmed the other major varieties are the saltwater or freshwater pearl, which both have their own different properties.
Saltwater pearls are found in pearl oysters which live in the ocean, and produce the classic round white or cream pearls that have remained so desirable and sought after throughout history. Comparing farmed pearls, saltwater pearls are often rounder than those from freshwater molluscs because they are made by inserting a bead into the oyster to encourage the shape. The popular Japanese Akoya pearl is a cultured saltwater pearl and is highly desirable for use in jewellery because of its large size and rounded shape, making them more expensive than the freshwater variety. It is still possible to find natural saltwater pearls in the ocean, but they are becoming more and more rare because of increased levels of pollution.
The most common type of pearl available today are freshwater pearls, which are mostly produced in China using freshwater mussels and come in a huge variety of shapes, sizes and colours. The natural colours of freshwater pearls are various shades of white, pink, cream and lilac but they are available as jewellery dyed in every colour of the rainbow. It is easier to farm freshwater pearls than saltwater, making them cheaper to buy as jewellery, though it is rare for them to be perfectly round and a necklace of cultured freshwater pearls will hardly ever be all the same size and shape.