Pearl
Pearl
Pearls are gems of biological origin: they form inside certain mollusks (pearl oysters and mussels) in response to irritation. To protect themselves, the animal deposits layer upon layer of nacre, a material composed primarily of aragonite crystals (calcium carbonate) bound together by an organic matrix called conchiolin. This architecture of fine, microscopic "tiles" acts as a stack of interfaces that diffuse and reflect light, creating the silky luster and sometimes the iridescence (orient) of the finest pearls. Visual quality depends greatly on the thickness and regularity of the nacre: the more uniform the layers, the more luminous and deep the pearl appears.
There are natural pearls (rare) and cultured pearls, where human intervention involves inserting a nucleus or graft to guide formation, while the mollusk then performs all the work of nacre deposition. Saltwater and freshwater pearls are often distinguished by their internal structure and shapes, ranging from perfectly round to baroque, each with its own charm. The color—white, cream, pink, gray, black, champagne—depends on the species, the environment, and the pigments present in the nacre. Unlike most gemstones, pearls are relatively soft (approximately 2.5 to 4 on the Mohs scale), which explains why they scratch more easily.
They are also sensitive to acids and chemicals: perfume, hairspray, chlorine, or vinegar can dull their surface. It is therefore advisable to apply them last, after cosmetics, and to gently wipe them with a cloth after use. For storage, it is best to keep them separate from harder jewelry to avoid micro-scratches. At the crossroads of biology, carbonate chemistry, and optics, the pearl is a natural marvel: a “living” gem, slowly shaped, layer by layer, by time and the care of the mollusk.