Big C, little C, what begins with C? This curving crescent of carbonate and quartz clinging to the coast. There is CloudSat and CALIPSO. Contrails from jets cruising over cumulus clouds. The Corolis force, chlorofluorocarbons, and crafty coccolithophores! An astronaut captured this photograph of an artificial island at the southern end of Bahrain Island on Jan. 23, 2011. The beach sand on tropical islands is mostly made up of calcium carbonate from the shells and skeletons of marine organisms.