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
Pearl Krabs Grandma's Apron, a store for elderly residents on the ground floor of the shopping center. Beatrice, her boss at Grandma's Apron, is voiced by actress Betty White. The disparity in species between Pearl and her father has never been explained directly in an episode, but merchandise makers and production crew members have stated that Mr. Krabs was once married to a whale who gave birth to Pearl. A trivia book penned by former "SpongeBob" writer David Fain in 2000 states that Pearl "takes after her mother," implying that she is the biological offspring of Mr. Krabs and a whale. According