The nacre of the pearl is the build up mainly of Calcium Carbonate or Mother of Pearl on the seed that is inserted into the pearl shell. These are called cultured pearls. The seeding of a pearl is a very specialised technique. Pearls are farmed in Broome, Western Australia and they are from large shells. The Chinese have developed a large fresh-water pearl industry but the shells are much smaller and so is the pearl. They are usually spherical but can be other shapes as well.
How do you tell pearls from imitations? Because the nacre forms in layers when you rub the pearl with your front teeth they feel gritty. By comparison imitation pearls feel smooth when rubbed against the front teeth.
The shells are clamped into a bracket that houses 6-10 shells depending on their size and inserted on racks that are lowered into the sea to a depth of 2-6metres. These are inspected regularly for cleaning and to check the development of the pearl. They are harvested after 12 months in Australia when the nacre has reached a certain thickness.
And then the fun begins as the pearls are sorted into sizes and then graded for quality and colour. And only then can the process of collecting matching pearls to form a necklace start! It is a very labour-intensive industry which explains why those lovely South Sea pearls cost so much.
Pearls do not like perfumes, cosmetics and hair spray or perspiration. They have a life expectancy of 100-150 years. The quality then deteriorates with time. They are such a special organic gemstone.