Iron: geological information

Iron is not found as the free metal in nature. The most common ore is haematite (iron oxide, Fe203). Iron is found in other minerals such as magnetite, which is seen as black sands along beaches. The core of the earth, more than 2000 in radius, is composed largely of iron. The metal is the fourth most abundant element by weight in the earth's crust.

Iron is found native in meteorites known as siderites.

Abundances of iron in various environments

In this table of abundances, values are given in units of ppb (parts per billion; 1 billion = 109), both in terms of weight and in terms of numbers of atoms. Values for abundances are difficult to determine with certainty, so all values should be treated with some caution, especially so for the less common elements. Local concentrations of any element can vary from those given here an orders of magnitude or so and values in various literature sources for less common elements do seem to vary considerably.

Abundances for iron in a number of different environments. Use the links in the location column for definitions, literature sources, and visual representations in many different styles (one of which is shown below)
Location ppb by weight ppb by atoms
Universe 1100000 20000
Sun 1000000 30000
Meteorite (carbonaceous) 220000000 77000000
Crustal rocks 63000000 23000000
Sea water 3 0.33
Stream 670 12
Human 60000 6700

The chart above shows the log of the abundance (on a parts per billion scale) of the elements by atom number in our sun. Notice the "sawtooth" effect where elements with even atomic numbers tend to be more strongly represented than those with odd atomic numbers. This shows up best using the "Bar chart" option on the chart.

cartogram depicting abundance of elements in the earth's crust
A cartogram depicting the abundance of elements in the earth's crust. Squares for each element are distorted in proportion to the numerical value of the abundance.

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