Arlington & Co. Hatton Garden – Pearls.
It is a myth that a pearl is created by grains of sand penetrating the shell of an oyster. Most pearls have at their centre a tapeworm larva that the oyster has inadvertently consumed. It deals with the parasite by spraying it with the same excretion , nacre, that it uses to coat the inside of it’s shell. The oyster then continues to spray and coat the larva for the rest of it’s life, so the larger the pearl the longer it’s host has lived.
Only one in 10,000 oysters will yield a pearl of good quality, sufficient enough to count as a jewel.