MCQ Detailed View

Pearls are organic gems formed inside certain mollusks, such as oysters and mussels, as a defense mechanism against foreign particles. When an irritant, like a grain of sand or a parasite, enters the mollusk’s shell, the organism secretes layers of a smooth, hard substance around it, eventually forming a pearl.

The main chemical component of pearls is calcium carbonate (CaCO₃). In pearls, this calcium carbonate is primarily in the form of aragonite, a crystalline mineral that gives pearls their hardness and distinctive luster. In addition to calcium carbonate, pearls can also contain small amounts of magnesium carbonate (MgCO₃). Magnesium carbonate can be naturally present due to trace minerals absorbed from seawater during the pearl’s formation.

These minerals are bound together by a small amount of organic material, often referred to as conchiolin, which acts like a natural glue. This structure is what we call nacre or mother-of-pearl, which is responsible for the pearl’s iridescent shine.

The exact ratio of calcium carbonate to magnesium carbonate can vary depending on the species of mollusk, its habitat, and environmental conditions. Saltwater pearls and freshwater pearls may have slightly different compositions, but calcium carbonate always makes up the majority of the mineral content.

Because of their mineral composition, pearls are relatively soft compared to gemstones like diamonds. They require special care to maintain their shine, avoiding exposure to acids, chemicals, and excessive heat.

In simple terms, pearls are mainly calcium carbonate with small amounts of magnesium carbonate, arranged in layers that create one of nature’s most elegant and valuable natural gems.