Editing Oyster (section)

===Pearl oysters===

[[File:Pearl Oysters.jpg|thumb|right|Removing a [[pearl]] from a pearl oyster|alt=Photo of opened oyster in bowl with person using a knife to remove the pearl]]
{{Main|Pearl oyster}}
Almost all shell-bearing mollusks can secrete pearls, yet most are not very valuable. Pearls can form in both saltwater and freshwater environments.

[[Pearl oyster]]s are not closely related to true oysters, being members of a distinct family, the feathered oysters ([[Pteriidae]]). Both [[cultured pearl]]s and [[natural pearl]]s can be extracted from pearl oysters, though other molluscs, such as the freshwater [[mussel]]s, also yield pearls of commercial value.

The largest pearl-bearing oyster is the marine ''Pinctada maxima'', which is roughly the size of a dinner plate. Not all individual oysters produce pearls.

In nature, pearl oysters produce pearls by covering a minute invasive object with [[nacre]]. Over the years, the irritating object is covered with enough layers of nacre to become a pearl. The many different types, colours and shapes of pearls depend on the natural [[pigment]] of the nacre, and the shape of the original irritant.

Pearl farmers can culture a pearl by placing a nucleus, usually a piece of polished mussel shell, inside the oyster. In three to seven years, the oyster can produce a perfect pearl. Since the beginning of the 20th century, when several researchers discovered how to produce artificial pearls, the cultured pearl market has far outgrown the natural pearl market.<ref>{{cite journal |title       = A History of the Cultured Pearl Industry
 |year = 2013
 |publisher   = [[BioOne]]
 |doi = 10.2108/zsj.30.783
 |last1 = Nagai
 |first1 = Kiyohito
 |journal = Zoological Science
 |volume = 30
 |issue = 10
 |pages = 783–793
 |pmid = 24125642
 |s2cid = 1429376
 |doi-access = free
 }}</ref>