Thulium is the 2nd rarest rare earth elements, only next to the man-made Promethium.
Its primary uses are in making crystal and lasers.
Another viatal application of thulium is in the Medicine area, It has been used for portable X-ray sources. Besides medical applications, the x-ray devices can be used to detect defects in mechanical and electronic components that is not conveniently accessible. least amount of protection is needed, only a small cap of lead is enough.
Thulium can also be used in magnetic and ceramic materials for microwave applications.