A pearl is a gem that grows inside certain mollusks from layers of nacre. Natural pearls form with no human help; cultured pearls need human care.
In more detail
To culture a pearl, a technician inserts mantle tissue, often with a shell bead, into a host mollusk. Akoya, South Sea and Tahitian cultured pearls are saltwater; freshwater cultured pearls are the most produced. Labs traditionally separate natural from cultured pearls with X-radiography. Pearl is very soft, and acids, cosmetics and perfume can damage it; never use ultrasonic or steam cleaners.
Related terms
- Dyeing: Dyeing is adding a colored substance to a gem's fractures or pores to change its color.
- Coating: Coating is a thin film, paint or ink on the surface of a gem that changes its color or look.
- Hardness (Mohs): Hardness is a gem's resistance to scratching. Gemologists rank it on the Mohs scale, on which diamond is 10.
- Treatment: A treatment is any process, other than cutting and polishing, that changes a gem's color or apparent clarity. Anyone who sells a treated gem must disclose the treatment.