Definition of "calcium carbonate" []

• A colorless or white crystalline compound, CaCO3, occurring naturally as chalk, limestone, marble, and other forms and used in a wide variety of manufactured products including commercial chalk, medicines, and dentifrices. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Several hoses did reach through the air lock, but their inner ends entered tanks in which pseudolife forms precipitated carbon dioxide as calcium carbonate — they simply provided fertilizer for the oxygenmakers."