Last modified on 12 July 2016, at 22:56


Objects which are calcareous in nature are composed of or contain calcite or calcium carbonate. Chalk and limestone are calcareous, being composed of calcium carbonate. Certain groups of sea creatures (calcarea, phytoplankton, and sea urchins for example) have calcareous skeletal structures, which accumulate on ocean floors, and is a major factor in how coral is formed.