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
The Pearl-Qatar project was first revealed, the initial cost of constructing the island stood at $2.5 billion. It is now believed the project will cost $15 billion upon completion. The name "The Pearl" was chosen because the island is being built on one of Qatar's previous major pearl diving sites. Qatar was one of the major pearl traders of Asia before the Japanese introduced cheaper more affordable pearls just before Qatar's oil boom. The Pearl Qatar will help represent Qatar's rich past in the pearl industry. Once completed The Pearl will resemble a string of pearls. Residential development on the island is