Per Theodore Cleve of Sweden
Not necessary for life.
Named from Thule, an ancient name for Scandinavia, thulium is a soft, silvery-gray metal, soft enough to be cut with a knife. It is the rarest of the lanthanide metals, excluding radioactive promethium. Thulium is an active metal, reacting with air, water and acids. When thulium is irradiated, it gives off X-rays. Consequently, it is used in portable X-ray machines that do not need external power. It is also used to produce magnetic ceramics and alloys with other metals. It serves as a medical isotope.
Thulium has no known biological use. It does act to stimulate the metabolism.
Role in Life Processes
No known benefit for life processes in plants and animals.
Thulium is chiefly obtained from bastnasite and monazite, where it occurs as an impurity. It is mined in the USA, China, Russia, Australia, and India.