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 Black Pearl (play) The Black Pearl (play) The Black Pearl () is a three-act comedy by the 19th-century French playwright Victorien Sardou that was first performed in 1862 in Paris. The play is based upon a story written by Sardou and first published in December 1861 under the title The Medallion. In 1825, in Amsterdam, Messieurs Balthazar and Cornelius sit down to supper during a particularly strong thunderstorm. Balthazar informs Cornelius that he is aware that Cornelius is in love with Christiane, who had been raised by Balthazar’s mother, and is practically his sister. He gives his blessing to a marriage between Cornelius