Pearls

Pearls fit into two categories: freshwater and saltwater. As their name implies, freshwater pearls are formed in freshwater mussels that live in lakes, rivers, ponds and other bodies of fresh water. Most freshwater cultured pearls sold today come from China. By contrast, saltwater pearls grow in oysters that live in the ocean, usually in protected lagoons. Akoya, South Sea and Tahitian are the three main types of saltwater pearls.

The difference between natural and cultured pearls focuses on whether the pearl was created by nature, without human intervention, or with human aid. Pearls are formed inside the shell of certain bivalve mollusks. As a response to an irritant inside its shell the mollusk creates a pearl as a defense mechanism. The mollusk will deposit layers of calcium carbonate (CaCO3) in the form of the minerals aragonite or calcite (both crystalline forms of calcium carbonate) held together by an organic horn-like compound called conchiolin. This combination of calcium carbonate and conchiolin is called nacre, or as most know it, mother-of-pearl. The commonly held belief that a grain of sand acts as the irritant is in fact rarely the case.

The largest pearl ever found came from the Philippines in 1934. Although referred to as a pearl, it is actually a non-nacreous calcareous concretion - gemologically speaking, it is not actually a pearl. It weighs 14 lb (6.4 kg) and was discovered by an anonymous Filipino Muslim diver off the island of Palawan in 1934. Later, a Palawan chieftain gave the pearl to Wilbur Dowell Cobb in 1936 as a gift for having saved the life of his son. The pearl had been named the Pearl of Allah by the Muslim tribal chief because it resembled a turbaned head. In 1980, Cobb's heirs sold it to a jeweler in Beverly Hills, California, for $200,000. It is now estimated to be worth upwards of $40,000,000! Currently, the Philippines produces both white and black pearls 8 to 20mm. However, they are most known for colors ranging from silvery white to champagne gold. The south sea pearl is the national gem of the Philippines.