Green'sānd, n.

n. (Geol.) A variety of sandstone, usually imperfectly consolidated, consisting largely of green particles of a mineral called glauconite.

Greensand is often called marl, because it is a useful fertilizer. The term is also applied to beds of the lower and middle part of the cretaceous formation in England, which include among them some of the green-sand layers. The greensand beds of the American cretaceous belong mostly to the upper cretaceous. Green-sand occurs also in rocks of other ages, from the Silurian to the Tertiary, and has been found in Rhizopod and other shells of modern date, obtained from the bottom of the ocean. The forms of the grains of glauconite, both in ancient and modern deposits, are often casts of the shells of Rhizopods. Dana.