Sunday, April 15, 2012

How to make iron (2) Iron on planet Earth

Mineral photos: Hematite

Mineral Information Institute from where the above image of a block of hematate is has web pages full of educational resources for students and teachers. Among other things, they have the following to say about iron:

Iron (Fe) is a metallic element and composes about 5% of the Earth’s crust. When pure it is a dark, silvery-gray metal. It is a very reactive element and oxidizes (rusts) very easily. The reds, oranges and yellows seen in some soils and on rocks are probably iron oxides.

The inner core of the Earth is believed to be a solid iron-nickel alloy.

Iron-nickel meteorites are believed to represent the earliest material formed at the beginning of the universe.

Studies show that there is considerable iron in the stars and terrestrial planets: Mars, the "Red Planet," is red due to the iron oxides in its crust.

Iron is one of the three naturally magnetic elements; the others are cobalt and nickel. Iron is the most magnetic of the three. The mineral magnetite (Fe3O4) is a naturally occurring metallic mineral that is occasionally found in sufficient quantities to be an ore of iron.

The principle ores of iron are Hematite, (70% iron) and Magnetite, (72 % iron). Taconite is a low-grade iron ore, containing up to 30% Magnetite and Hematite.

Hematite is iron oxide (Fe2O3). The amount of hematite needed in any deposit to make it profitable to mine must be in the tens of millions of tons. Hematite deposits are mostly sedimentary in origin, such as the banded iron formations (BIFs). BIFs consist of alternating layers of chert (a variety of the mineral quartz), hematite and magnetite. They are found throughout the world and are the most important iron ore in the world today.

Their formation is not fully understood, though it is known that they formed by the chemical precipitation of iron from shallow seas about 1.8-1.6 billion years ago, during the Proterozoic Eon.
Mineral Information Institute

It is quite amazing to my mind how things come together, Geology and the history of Earth's crust, formation of planets, production of iron in giant stars...

Amazing and fascinating!

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