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n. 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.

n. A greenish form of mica found in greensand

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.

n. 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.

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

"Iron likewise combines with a considerable variety of substances other than oxygen; and some of these compounds, as for instance iron carbonate (siderite), iron silicate (chamosite, glauconite, etc.), and iron sulphide (pyrite), are locally mined as iron ores."

mineral   

greensand