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
Bruce Pearl November 20, 2010, the SEC ordered Pearl to sit out Tennessee's first eight SEC games. After finding out about additional NCAA violations, as well as a violation of the school's substance abuse policy by a player, Tennessee fired Pearl on March 21, 2011—three days after the Vols' blowout loss to Michigan. On August 23, 2011, Pearl was given a three-year show-cause penalty for lying to the NCAA, effective until August 23, 2014. This meant that the sanctions imposed on Pearl would remain in force if he was hired by an NCAA member school within that period. Specifically, he was prohibited