greensand
/ˈɡrinˌsænd/
noun
- A greenish sedimentary rock or sand that contains the mineral glauconite, often used as a soil conditioner or water softener.
- Greensand is mined in several parts of the United States.
- Gardeners sometimes add greensand to improve clay soil.
- The cliffs along the coast are made of ancient greensand.