On the inside of an oyster’s shell, there’s a layer called the mantle that safeguards its vital organs. When a grain of sand sneaks its way between the mantle and the shell — as is bound to happen in the unruly current of the ocean — the oyster produces a protective substance called nacre, which coats the grit to reduce irritation. Little by little, layer by layer, it wraps around and around the discomfort until it forms an iridescent gem.
Sometimes, this process takes six months. Larger pearls can take up to four years to develop. Only the oysters whose first pearls prove to be well-formed — the ones that are particularly good at gently transforming their unease into art — repeat the process.