Glauconite

[glɔ:kәnait]

(noun.) a green mineral consisting of hydrated silicate of potassium or iron or magnesium or aluminum; found in greensand.

Editor: Samantha--From WordNet

(n.) The green mineral characteristic of the greensand of the chalk and other formations. It is a hydrous silicate of iron and potash. See Greensand.

Checker: Steve

n. the mineral a silicate of iron which gives a green colour to some of the beds of the greensand strata whence their name.—adj. Glauconit′ic.

Checker: Velma