Pearls are gems formed in the living haven of both marine and fresh water mollusks. Responding to an irritant within its system, a mollusk coats a particle with the same two substances it uses to build its shell. This build up of material in alternating layers forms a composite material called nacre. The thickness of the luminescent nacre determines the luster of the pearls. Natural pearls, called ‘oriental pearls' are rare; the chance of their formation is only about one in every 10,000 mollusks.
The culturing of pearls, the intrusion of a rounded piece of shell into an oyster to spark the pearl formation, has only been accomplished in the last century. However, top quality pearls remain rare. Even with today's methods, only 5% of the cultured pearls produced are top grade, gem quality.
Pearls are soft and can be damaged by careless cleaning and scratching. They should be kept separate from other jewelry in their own soft cases or bags. While wearing pearls keeps them from drying out and losing their luster, perfumes, makeup, hair products, chlorine, household cleaners, and even perspiration can have a damaging effect. Pearls should be wiped gently with a very soft damp cloth after wearing. Never use an ultrasonic cleaner on pearls or have them steam cleaned. Abrasive materials and household cleaners should not be used to clean pearls. The only jewelry cleaners that should be used are those labeled as being safe for pearls.