Not only is pearl the birthstone for June, but it is also the gem representing the 3rd and 30th anniversaries. The main types of pearl used in jewelry are Akoya, Tahitian, South Sea, and fresh water.
Pearls of decent quality are seldom found naturally. The rate of them being found in nature is less than 1 in every 10,000 wild oysters. Very rarely, some varieties of mollusk can create a pearl by coating an irritant (usually a foreign organism) in the same material it uses to make its shell -- nacre (aragonite) -- which is also called mother-of-pearl.
Nacre is a smooth, shiny substance that is made of layers upon layers of aragonite (alternating with conchiolin). Nacre is what gives a pearl its unique appearance. It can come in a wide range of natural colors, such as gold, black, and white. These colors are determined by the mollusk’s inner lip.
The hardness for pearls ranges from 2.5 to 4.5 on the Mohs hardness scale, so care should be taken to avoid scratching them. Since pearls are the only organic birthstones, they are also susceptible to damage from chemicals in cleaning solutions, cosmetics, and hair sprays. Pearls should not be put in an ultra-sonic device nor should they be cleaned with a steamer. Gently wiping after wear will remove the body’s naturally acid oils which will help the luster stay high and extend the life of a strand of pearls.