Pearls are made how, I hear you ask?
Pearls are formed inside the shell of particular types of mollusks: as a defense mechanism to a potentially threatening irritant such as a parasite or a foreign body inside its shell, the mollusk secretes a protein which forms around the irritant, which in turn creates a pearl around the irritant to seal it off from potentially causing damage to the mollusks insides.
The difference between natural and cultured pearls focuses on whether the pearl was created spontaneously by nature — without human intervention — or with human aid.
The mantle (or shell) of the mollusk deposits layers of calcium carbonate (CaCO3) in the form of the mineral aragonite or a mixture of aragonite and calcite (both crystalline forms of calcium carbonate) held together by an organic horn-like compound called conchiolin. The combination of aragonite and conchiolin is called nacre, which makes up mother-of-pearl.
The commonly held belief that a grain of sand acts as the irritant is in fact rarely the case. Typical irritants include organic material, parasites, or even damage that displaces mantle tissue to another part of the animal’s body into the inside of the mollusks membrane. These small particles or organisms enter the animal when the shell valves are open for feeding or respiration. In cultured pearls, the irritant is typically a cut piece of the mantle, together with processed shell beads, the combination of which the animal accepts into its body.
Natural pearls are nearly 100% calcium carbonate and conchiolin. It is thought that natural pearls form under a set of accidental conditions when a microscopic intruder or parasite enters a bivalve mollusk, and settles inside the shell. The mollusk, being irritated by the intruder, secretes the calcium carbonate and conchiolin to cover the irritant. This secretion process is repeated many times, forming many layers of nacre thus producing a pearl. Natural pearls come in many shapes, with perfectly round ones being comparatively rare.
The rounder and more perfect the pearl is the more rare and more valuable they become, in a similar way to the way diamonds are valued as they become bigger and better in quality.
Without getting overly technical here, a pearl is basically formed when a foreign body enters the animals membrane while the shell is open for feeding or breathing. The mollusk then secretes a protein called nacre to cover the foreign body, which will help minimise any damage it can potentially do to the muscular structure inside the shell. It does not stop there as the mollusk will continually secrete the nacre to form many many layers over the foreign body, which over time creates the pearl we are after.
Sam Kritsotakis
