Abundances In this table 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 much 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 by orders of magnitude.
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Abundance
ppb by weight
ppb by atoms
Universe
2
0.02
Sun
1
0.005
Meteorite (carbonaceous)
100
10
Crustal rocks
8700
1300
Sea water
0.0006
0.000026
Stream
0.03
0.0002
Human
no data
no data
Notes
Praseodymium is never found in nature as the free element. Praseodymium is found in the ores monazite sand [(Ce, La, etc.)PO4] and bastn°site [(Ce, La, etc.)(CO3)F], ores containing small amounts of all the rare earth metals. It is difficult to separate from other rare earth elements.
