Rare Earths, Magnets, etc.
High intensity magnets are currently made with rare earth elements. REEs principally occur in monazite. According to this paper, there are 1e9 kg of thorium (and presumably rare-earth bearing) ores. Presume monazite ores, which are 5% to 10% thorium oxide, and 55% to 60% rare earth oxides.
The crustal abundance of rare earths is (presumably ppm by weight):
Element |
ppm |
frac |
AMU |
PO4 |
monaz |
total MT |
Priuses |
Cerium |
60.0 |
0.2946 |
140 |
0.1191 |
0.0979 |
3.2 |
|
Yittrium |
33.0 |
0.1620 |
89 |
0.0836 |
0.0539 |
1.7 |
|
Lanthanum |
30.0 |
0.1473 |
139 |
0.0598 |
0.0490 |
1.6 |
160 million |
Neodymium |
28.0 |
0.1375 |
144 |
0.0546 |
0.0457 |
1.5 |
1500 million |
Scandium |
20.0 |
0.0982 |
45 |
0.0666 |
0.0326 |
1.1 |
|
Praseodymium |
8.2 |
0.0403 |
141 |
0.0162 |
0.0134 |
0.4 |
|
Samarium |
6.0 |
0.0295 |
150 |
0.0114 |
0.0098 |
0.3 |
|
Gd Dy Yb Er |
14.2 |
0.0697 |
157 |
0.0263 |
0.0232 |
0.8 |
|
Eu Ho Tr Tm Lu |
4.3 |
0.0211 |
152 |
0.0081 |
0.0070 |
0.2 |
|
Total |
203.7 |
1 |
|
0.4458 |
0.3325 |
|
|
Fraction metals |
0.5542 |
|
|
||||
Fraction metals 55% RE monazite |
0.3325 |
|
11 |
||||
The mass percentage assumes the mineral is a PO₄ phosphate (95 AMU ).
The crustal abundance is used here as a proxy for relative abundance in REE ores. Most of the REEs are not concentrated into ores, and are not economically recoverable (we cannot afford to run the entire earth's crust through magnetic separation - not enough magnets!). None are concentrated in other solar system objects, none of which have plate tectonics and ocean-driven beneficiation.
Major deposits |
MT |
China |
36 |
United States |
13 |
Australia |
|
India |
|
World |
99 |
A Prius uses 1 kg of neodymium in the motor, and 10 kg of lanthanum in the battery. There are enough reserves of rare earths worldwide to produce only 160 million Priuses of the current design.
Launch loop magnet rails will also require high-strength magnets. Those will be recycled, but some will be lost. Presume that skyrocketing rare earth prices will drive frantic research for clever nanomaterial substitutes; that will allow us to make more high-energy-density magnets.