Thulium (Tm)
Thulium (Tm) is contained in the following rare earth mineral:
Fergusonite
Area of application: A silvery-gray metal, thulium is one of the least abundant rare earths. Its isotopes are widely used as the radiation device in portable X-rays, making thulium a highly useful material. Thulium is also a component of highly efficient lasers with various uses in defense, medicine and meteorology.
References
https://en.wikipedia.org
http://images-of-elements.com/thulium.php