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 Qing Ding Pearl The Qing Ding Pearl The Qing Ding Pearl (《慶頂珠》, simplified 庆顶珠) is a Chinese play. It dates to the Song Dynasty and is still performed in adapted forms in the Beijing Opera. The play is known by other titles: Two sections (折 zhe) of the main play are sometimes performed separately as The Fisherman's Revenge《漁夫恨》 or A Fisherman Kills a Family (《打漁殺家》, simplified 打渔杀家 dayu sha jia) also Collecting the Fishing Tax (《討漁稅》 "taoyushui"). The play tells the story of Xiao En (whose real identity is Ruan Xiaoqi from "Water Margin"), a poor fisherman and his daughter who seeks bloody