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 Harbor and the Explosions Pearl Harbor and the Explosions Pearl Harbor and the Explosions was a musical act from San Francisco, California. Forming in 1978, the new wave band had limited success in the late 1970s and early 1980s, with their debut single, "Drivin'", reaching the lower end of the American top 40 charts in 1980. That same year, they released a self-titled LP which included the song "Shut Up and Dance", which received considerable airplay, particularly in the Bay Area. The vocalist, Pearl E. Gates (also known as "Pearl Harbor", and later "Pearl Harbour" (British and Canadian spelling), would eventually marry Clash bassist