siderite (sĭdˈərĪt) [key] or chalybite kălˈĭbĪt, a mineral, varying in color from brown, green, or gray to black and occurring in nature in massive and crystalline form. A carbonate of iron, FeCO3, it serves as an iron ore, especially in the British Isles. It is widely distributed, being found also in the United States, Europe, South America, and Australia.
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