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) day, Kino goes to sell his pearl. Unknown to him, the pearl dealers in La Paz are in cahoots with each other, secretly conspiring to make it appear as though the prices offered are competitive when they are defrauding the natives. They offer Kino a thousand pesos for the pearl when Kino believes that it is worth fifty thousand. Kino refuses to sell to the pearl dealers and decides to go to the capital instead. That night, Kino is attacked by more thieves, and Juana once again reminds him that the pearl is evil. However, Kino vows that he will