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.
Taconite is a silica-rich iron ore that is considered to be a low-grade
deposit. However, the iron-rich components of such deposits can be processed to
produce a concentrate that is about 65% iron, which means that some of the most
important iron ore deposits around the world were derived from taconite.
Taconite is mined in the United States, Canada, and China.
Iron is essential to animal life and necessary for the health of plants. The
human body is 0.006% iron, the majority of which is in the blood. Blood cells
rich in iron carry oxygen from the lungs to all parts of the body. Lack of iron
also lowers a person’s resistance to infection. |
