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 barley its caloric, protein, vitamin and mineral content, though some varieties are higher in lysine. It is used mainly in soups, stews, and potages. It is the primary ingredient of the Italian dish orzotto. Pearl barley Pearl barley, or pearled barley, is barley that has been processed to remove its hull and bran. All barley must have its fibrous outer hull removed before it can be eaten; pearl barley is then polished to remove the bran layer. It is the most common form of barley for human consumption because it cooks faster and is less chewy than other, less-processed forms of