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
BlackBerry Pearl and in Canada through Rogers, Telus, and Bell Mobility. The phone has been known by many names, from the original codename BlackBerry "Kickstart" name to the current BlackBerry Pearl 8220 Smartphone name. A CDMA version is available for Verizon and Alltel known as the 8230. The Pearl Flip is very similar to the original Pearl and uses the same predictive text input that the Pearl uses. It has a 2.0-megapixel camera and video recording. It is the first BlackBerry to feature Wi-Fi and mobile calling in a new flip design. This 3G line came with 360 x 400, 2.25" TFT