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 Street Schoolhouse Pearl Street Schoolhouse The Pearl Street Schoolhouse, also known as District 11 Schoolhouse, is located south of the junction of Awosting and Decker roads in the Town of Shawangunk, New York, United States. It was built around 1850. The schoolhouse name is derived from the tendency of the Jansen family to speak often of Pearl Street in what is today Lower Manhattan. The homes of early settlers Thomas and Johannes are within a mile (1.6 km) of each other. Eventually, the whole area they lived in became known as Pearl Street. The building, now a private home, was added to