Most people when they imagine a pearl are picturing perfect large round spherical gems, creamy white in colour with a shimmery iridescent surface. In fact pearls come in many different shapes, sizes and colours 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. Apart from whether a pearl is cultured or natural the other major varieties are the saltwater or freshwater pearl, each of which have their own qualities.

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. Cultured saltwater pearls are more likely to be round than those from freshwater molluscs because they are made by inserting a bead into the oyster to encourage the shape. The Japanese Akoya is the most popular type of cultured saltwater pearl and is highly desirable for use in jewellery because of its large size and rounded shape, meaning that this type usually costs more than cultured freshwater pearls. It is still possible to find natural saltwater pearls in the ocean, but they are becoming more and more rare due to pollution in the seas.

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. Freshwater pearls come in the natural colours of whites, pinks, creams and lilacs but they are often dyed to produce a whole rainbow of other colours for jewellery. Freshwater pearls are easier to farm succesfully than saltwater pearls, and for this reason they are slightly cheaper to buy, 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.