iron: Natural Occurrence

Iron is an abundant element in the universe; it is found in many stars, including the sun. Iron is the fourth most abundant element in the earth's crust, of which it constitutes about 5% by weight, and is believed to be the major component of the earth's core. Iron is found distributed in the soil in low concentrations and is found dissolved in groundwaters and the ocean to a limited extent. It is rarely found uncombined in nature except in meteorites, but iron ores and minerals are abundant and widely distributed.

The principal ores of iron are hematite (ferric oxide, Fe₂O₃) and limonite (ferric oxide trihydrate, Fe₂O₃·3H₂O). Other ores include siderite (ferrous carbonate, FeCO₃), taconite (an iron silicate), and magnetite (ferrous-ferric oxide, Fe₃O₄), which often occurs as a white sand. Iron pyrite (iron disulfide, FeS₂) is a crystalline gold-colored mineral known as fool's gold. Chromite is a chromium ore that contains iron. Lodestone is a form of magnetite that exhibits natural magnetic properties.

Sections in this article:

• Introduction
• Wrought Iron
• Cast Iron
• Production and Refining
• Natural Occurrence
• Compounds
• Properties
• Bibliography

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