Thulium is a chemical element with symbol Tm and atomic number 69.
- Radioactive isotope Tm is produced by bombarding thulium in a nuclear reactor. It has a half-life of 128 days and is used as a portable source of x-rays.
- Thulium is used to dope yttrium aluminum garnets (YAG) used in lasers.
- Thulium is also used in alloys with other rare earth metals.
- Thulium is used in euro banknotes for its blue fluorescence under UV light to defeat counterfeiters.
- Thulium is considered to be non-toxic.
Source: Chemicool, http://www.chemicool.com/elements/thulium.html