Glauconite, GLAW kuh nyt, is a bright green mineral that looks like tiny flakes of the mineral mica, or small lumps of clay. Nearly pure glauconite, called greensand, is used as a water softener. Glauconite deposits occur in Colorado, New Jersey, and Wisconsin. Chemically, glauconite is a hydrous (water-containing) silicate of potassium and iron. It may have been formed originally from biotite (a dark-colored mica), but other minerals, and even organic matter, may change into glauconite. Glauconite is slowly forming from seawater.