Usually the original mineral was aragonite or calcite, and it has been replaced by silica (in ... well-cemented sediment in the middle of a relatively uncemented sedimentary rock). Indeed, the critter ...

Limestone, for example, is a sedimentary rock made exclusively of the mineral calcite (CaCO3). Glacier ice too, is a type of rock composed of crystals of water. In 2014, scientists proposed naming ...