The mean iron content of the earth’s crust is 5%. Iron is locked in ferromagnesian silicates in rocks at the earth’s surface mostly as green or black ferrous-ferric iron. The black ferrous-ferric form is magnetite, the red ferric oxide, hematite, and the yellow-brass ferrous sulfides are commonly cubic pyrite and orthorhombic spearhead-shaped marcasite. Iron also appears as white to dark brown ferrous carbonate (siderite) and green iron silicate, glauconite, which adds a greenish color to sedimentary rocks (Sect. 4.4).
Keywords
- Metallic Iron
- Iron Mineral
- Pyrite Oxidation
- Ferric Hydroxide
- Stone Surface
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