Uranium - 92U: 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.
| 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 |
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.
