Pearl or parasite enters a bivalve mollusk and settles inside the shell. The mollusk, irritated by the intruder, forms a pearl sac of external mantle tissue cells and secretes the calcium carbonate and conchiolin to cover the irritant. This secretion process is repeated many times, thus producing a pearl. Natural pearls come in many shapes, with perfectly round ones being comparatively rare. Typically, the build-up of a natural pearl consists of a brown central zone formed by columnar calcium carbonate (usually calcite, sometimes columnar aragonite) and a yellowish to white outer zone consisting of nacre (tabular aragonite). In a pearl cross-section
The Pearl (novel) The doctor also visits, and although Coyotito seems to be healing, the doctor insists that Coyotito still faces danger and treats him. Kino tells the doctor that he will pay him once he sells his pearl, and the doctor attempts to discern where the pearl is located (Kino had buried it in the corner of his hut). That night, a thief attempts to break into Kino's hut, but Kino drives him away. Juana tells Kino that the pearl will destroy them, but Kino insists that the pearl is their one chance and that tomorrow they will sell it. The next