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
Cora Pearl In his biography of Pearl, "The Pearl From Plymouth" (1950), author W. H. Holden writes that there is evidence that Pearl regularly sent money to both her mother in England and father in America. For Cora Pearl, money was for spending, for accumulating the luxuries of life and buying her way to a coveted perch in the upper echelons of society. Her jewel collection alone was valued at some one million francs; at one point, she owned three homes, and her clothing was made for her by the renowned couturier Charles Frederick Worth. As her career prospered, the gifts from