Pearls, natural or cultured, are formed when a mollusk produces layers of nacre (pronounced NAY-kur) around some type of irritant inside its shell. In natural pearls, the irritant may be another organism from the water. In cultured pearls, a mother-of-pearl bead or a piece of tissue is inserted (by man) into the mollusk to start the process.
For both, the quality of the nacre dictates the quality of the luster, or shine of the pearl, which is very important to its beauty and its value. The surface of the pearl should be smooth and free of marks while the overall shape could be round, oval, pear-shaped, or even misshapen. Misshapen pearls are called baroque pearls.
While shopping for pearls, there are various lengths available:
A collar fits directly against the throat
A choker rests at the base of the neck
The princess length reaches near the collarbone
A matinee length is usually 20-24 inches
The Opera length is 30-36 inches
The longest length, known as a rope, refers to all strands longer than 36 inches