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Thulium (Tm, atomic number 69) was discovered in 1879 by Cleve Thulium occurs in small quantities along with other rare earths in a number of minerals. It is obtained commercially from monazite which contains about 0.007% of the element. Thulium is the least abundant of the rare earth elements, but with new sources recently discovered, it is now considered to be about as rare as silver, gold or calcium. Thulium is very difficult to separate from the other elements because it is so similar in size. It can be isolated by reduction of the oxide with lanthanum metal or by calcium reduction of a closed container. The element is silver/grey, soft, malleable and ductile. It can be cut with a knife. Due to the difficulty to separate it is very expensive and is not used often. It has a +2 and +3 oxidation state. Chemists are beginning to find uses for it and uses should increase in years to come. As with other lanthanides, thulium has a low to moderate acute toxic rating. It should be handled with care.

The few known uses for Thulium are as follows:

  • 169Tm bombarded in a nuclear reactor can be used as a radiation source in portable X-ray equipment.
  • 171Tm is potentially useful as an energy source.
  • Natural thulium also has possible use in ferries (ceramic magnetic materials) used in microwave equipment and it can be used in for doping fiber lasers.