Carbonate/ˈkɑːrbənət/ Definition 1 of 2Pro Tip 1/3Scientific Usage Often used in science, especially chemistry, geology, and biology. The researcher examined the carbonate levels in the sediment. Pro Tip 2/3Common Substances Carbonates are found in everyday materials, like chalk and limestone. Limestone consists mainly of calcium carbonate. Pro Tip 3/3Environmental Relevance Carbonates play a role in the carbon cycle and climate change discussion. Oceans absorb carbon dioxide and form carbonate compounds.