Pearl

Pearl is an organic gem, a biomineral grown inside mollusks from nacre, alternating microscopic layers of aragonite (a form of calcium carbonate) bound by the protein conchiolin. Pearls form when an irritant (a parasite, not a grain of sand - the sand myth is wrong) becomes lodged in a mollusk's tissue. The animal coats the irritant with nacre - alternating microscopic layers of aragonite (calcium carbonate) platelets and conchiolin (organic protein). These layers build up over years, eventually creating a pearl.

Nacre's beauty comes from its layered structure. The aragonite platelets are roughly the same thickness as the wavelength of visible light, so they act as a natural diffraction grating - splitting and reflecting light to create the luminous, iridescent quality called 'orient.' The more uniform and numerous the nacre layers, the finer the pearl's luster.

Natural pearls (formed without human intervention) are extraordinarily rare today. Virtually all pearls on the market are cultured - a technician surgically inserts a bead nucleus into the mollusk, which then coats it with nacre over 1-5 years. Kokichi Mikimoto patented the cultured pearl process in 1893, democratizing what had been the world's most exclusive gem.

Pearls are identified by their characteristic pearly luster, organic origin, and the 'tooth test' - rub a pearl gently against the biting edge of your front teeth. Genuine nacre feels slightly gritty (the edges of aragonite platelets), while plastic or glass imitations feel smooth.

Distinguish from shell pearls (coated glass beads - too perfect, too heavy), plastic imitations (smooth tooth test, lighter), and Majorica pearls (high-quality glass imitations from Mallorca). Under magnification, genuine nacre shows overlapping platelet edges; imitations show paint or coating layers.