Uranium: geological information

The most important uranium ore is uranite, usually called pitchblende. Uranite's formula is roughly UO2. Uranium is surprisingly common and is more plentiful than mercury, silver, or cadmium in the earth's crust, and is about as abundant as molybdenum or arsenic. Much of the earth's internal heat is thought to be attributable to nuclear reactions of uranium and thorium.

Abundances of uranium 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 uranium 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 0.2 0.001
Sun 1 0.004
Meteorite (carbonaceous) 10 1
Crustal rocks 1800 150
Sea water 3.3 0.086
Stream 0.04 0.0002
Human 1 0.03


Log abundance (by atom numbers) in our sun

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.

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uranium atomic number