Pearls may be a variety of colors, including white, pink and black. Any mollusk can form a pearl, although they are more common in some animals than in others. There are animals known as pearl oysters, which includes species in the genus Pinctada. The species Pinctada maxima (called the gold-lipped pearl oyster or silver-lipped pearl oyster) lives in the Indian Ocean and the Pacific from Japan to Australia and produce pearls known as South Sea Pearls. Other pearl-producing animals include abalones, conchs, pen shells,and whelks.
Pearls may also be found and cultured in freshwater mollusks and are often produced by species collectively called "pearl mussels." Some pearls are cultured - they do not form by chance in the wild, but are helped by humans, who insert a piece of shell, glass or mantle into a mollusk and wait for pearls to form. You can read more about this process here.
These are the parts of an oyster inside the shell:
- Mouth (palps)
- Abductor muscle
As the oyster grows in size, its shell must also grow. The mantle is an organ that produces the oyster's shell, using minerals from the oyster's food. The material created by the mantle is called nacre. Nacre lines the inside of the shell.