Mother of Pearl
Mother-of-pearl is the basic substance which is secreted by oysters and molluscs to form the inside of their shells.
It is the same substance which forms pearls. Until it was replaced by plastic in the mid-20th century mother-of-pearl was also used to produce shiny buttons for clothing. This was the case in Broome Australia, a well-known South Sea pearl producing area. Before South Sea pearls became the main product of the area, this small town thrived on the Pinctada maxima mother-of-pearl business.
Mother-of-pearl is now used extensively as the nucleus in pearl cultivation. The shell of a mussel is cut into squares and then run through a process which rounds the pieces into beads. These beads are then implanted into the oysters which will respond to the irritation by secreting nacre upon the mother-of-pearl beads to form the cultured pearl.