Molluscs that mature in lakes & ponds (as opposed to salt water) produce nacre. 'Nacre/mother of pearl', is an organic material formed by molluscs when creating shells or pearls.
Fresh water pearls, also known as 'cultured pearls' can come in all shapes and sizes. Irregular shaped pearls are plentiful making them affordable for jewellery makers, where as the rounder more uniform natural pearls are more expensive due to their rarity.
*this product is not suitable for vegans