A bead, known as the ‘nucleus’, is inserted inside the Akoya oyster. The nucleus stimulates the secretion of milky fluid called nacre (more commonly known as ‘Mother of Pearl’).
The nacre covers the nucleus thus forming a pearl. This process is known as ‘culturing’ and takes approximately three to six years. This time allows for the creation of a greater lustre than found in freshwater pearls.
Freshwater pearls are produced within a mussel without a bead inside. As they are non-nucleated, they are lighter in weight than saltwater pearls. The culturing process is far quicker: about twelve months, and this is invariably reflected in the price when compared to Akoya pearls.
PEARLS: SHAPE & COLOUR
Akoya pearls are spherical in shape. Irregular or semi-round pearls are often referred to as baroque.
Their natural colour is white, but they can have a pink or cream lustre. They can also be dyed with silver nitrate to produce black or grey pearls. Tahitian Pearl’s colour is influenced purely by diet and environment and not through any staining process.
Freshwater pearls can be produced in many shapes: round, oval, disc, rectangular.
The colour and shape of freshwater pearls are determined by the mussel’s diet and environment. They can be white or shades of pink, peach and mauve. They can otherwise be stained black and grey or heat treated for the chocolate and pistachio hues.
PEARLS: SIZE & VALUE
Cultured saltwater pearls are measured by the diameter. They are mainly produced in twelve different sizes: from 3 – 3.5mm to 8.5 – 9mm. Like diamonds, the larger the size, the greater the value. Pearls that are larger than 9mm and of high quality are scarce and therefore very expensive.
As freshwater pearls come in so many different shapes, the sizes can vary greatly. Oval shaped pearls can be as large as 15mm, although they are generally used for drop earrings and pendants rather than necklaces.
N.B. China are becoming evermore successful in their cultivation of round, freshwater pearls (some of which are also nucleated) but they are still, as yet, not on a par with the best Japanese Akoya cultured pearls.