Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3 (the other form being the mineral calcite). It is formed by biological and physical processes, including precipitation from marine
Calcite with quartz from Huanggang Mine, Inner Mongolia, China. The pictured specimen is 7cm tall. The quartz at the center of the stacked calcite disks is better exposed in some of the specimens that they have at the show. Photo credit: Jeffrey A. S