noun. A greenish mineral of the mica group, a hydrous silicate of potassium, iron, aluminum, or magnesium, (K,Na)(Al,Fe,Mg)₂(Al,Si)₄O₁₀(OH)₂, found in greensand and used as a fertilizer and water softener.

noun. A mineral which is essentially a hydrous silicate of iron and potassium. It is the “green earth” of the cavities of eruptive rocks, or the substance which gives the color to the grains of greensand and chalk.

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

noun. A greenish form of mica found in greensand

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

"Keller et al. (2004a,b) demonstrated that the impact breccia and the K-T boundary are separated by a 50 cm interval of sediments that contain (1) five thin glauconite clay layers, each of which represents deposition over tens of thousands of years, thus incompatible with tsunami or backwash deposition?"

mineral  

greensand