Did you know pearls could be cultivated just like any crop.

Does not require vast land or water body either. Pearl are manually induced into oysters and mussels in controlled environment and preserved as well. You can literally cultivate most types of pearls. Visually you can't tell apart naturally wild pearl and a cultivated pearl. However, chemical properties would differ just like a wild salon and farm salmon would. Their natural shape isn't necessarily round, they are cut, polished on various shapes and sizes. 

Swan prey on pearls of all types !! Img courtsey - Avatams.com