When a foreign object, such as a grain of sand, accidentally lodges in an oyster, it is coated with layer upon layer of a smooth, hard crystalline substance called nacre. After a period of time, this natural process produces the luminescent gem called pearl.
Natural, or Oriental, pearls are still cultivated in the Persian Gulf and Indian Ocean. However, most pearls sold today are cultured. The culturing process was developed during the first 30 years of the 20th century by Kokichi Mikimoto, founder of the company that still bears his name.
The quality of pearls varies dramatically, just like other gemstones. Like most of nature’s creations, only a small percentage is beautiful enough for use in jewelry.