Some sands contain magnetite, chlorite, glauconite, or gypsum. The green mineral glauconite is particularly common. Quartz dominated with subordinate feldspar, glauconite and sporadic phosphatic grains. It is an inorganic pigment derived from the minerals celadonite and glauconite. It has fine to medium grained sandstones with carbonate cement, glauconite and fossil fragments. Additional constituents include feldspar, glauconite and ferrous minerals of limonite ore. Saponite, talc, talc-saponite, nontronite, glauconite, and serpentine are all common on the seafloors on Earth. Particular minerals that can be used include green rust, magnetite, pyrite, and glauconite. The dominant minerals in the silicate facies are greenalite, minnesotaite, and glauconite. The glauconite "per se" will incorporate electrochemically bound water (CBW) because of the clay types. Thus references to "greensand marl" sometimes refer specifically to glauconite. Greensand glauconite is used as a water softener for its chemical-exchange properties. Glauconite is responsible for the green coloration of the Bright Angel. Glauconite has been called a marl in an old and broad sense of that word. At the broadest level, glauconite is an authigenic mineral and forms exclusively in marine settings.