It's a common misconception that pearls create other pearls. In reality, pearls are not living organisms and do not reproduce or create other pearls. Instead, pearls are made by marine oysters and freshwater mussels as a natural defence mechanism.
The Biological Process of Pearl Formation
Pearls are formed within certain mollusks, specifically oysters and mussels, as a protective response. This process is initiated when an irritant enters the mollusk's shell or its delicate body sustains damage.
What Triggers Pearl Growth?
Based on natural processes, pearl formation is typically triggered by:
- An irritant: Such as a parasite entering the shell.
- Damage: Injury to the mollusk's fragile internal body tissue.
Layers of Defense: How the Pearl Grows
As a natural defence against this intrusion or damage, the oyster or mussel isolates the irritant or damaged area. The mollusk's mantle tissue, which is responsible for shell growth, begins to secrete layers around the irritant.
The materials secreted are:
- Aragonite: A form of calcium carbonate, which is crystalline.
- Conchiolin: An organic protein substance that acts as a binding agent.
These are the very same materials that the mollusk uses to build its own shell. The mollusk slowly and continuously secretes these layers, one upon the other, surrounding the irritant. Over time, these concentric layers build up, creating the luminous object we know as a pearl.
This slow, layer-by-layer process is what gives pearls their unique depth and iridescence, often referred to as orient. The longer the layers are secreted, the larger the pearl becomes.
While this describes natural pearl formation, most pearls today are cultured pearls, where humans initiate this same biological process by intentionally introducing an irritant (like a bead or tissue piece) into a mollusk. However, the fundamental biological mechanism by which the mollusk creates the pearl layers remains the same.
