Thulium is a bright silvery metal, which slowly tarnishes in air and is reactive in water. It is extremely soft and can be cut with a knife. Thulium is an extremely rare chemical element (symbol Tm and atomic number 69) and it is never found in pure form in nature. It is found in small quantities in certain minerals, along with other rare earth elements. The occurrence of thulium in the crust of the earth is about 0.5 mg per kg. It is mostly extracted from the monazite ores, which are found in river sand. Due to its extreme rarity it is also very expensive (in 2005 a gram of pure thulium cost $70). Due to these factors it has only a few applications in the world today.
- It is used in certain types of powerful lasers and these are commonly used in the military, meteorology (the study of weather/atmosphere) and health. They are popular with laser based surgery because they are able to remove tissue without causing other damage.
- Thulium obtained from a nuclear reactor can be used as a radiation source for certain portable X-ray machines. The thulium in the devices is usable for about a year.
- A certain isotope of thulium (170T) is being used for a type of cancer treatment where the source of radiation is placed inside or near the area that requires treatment.
- Thulium can also be used in high-temperature superconductors.
- Thulium is used in Euro money to prevent counterfeiting. When exposed to UV light the thulium shows up as a blue fluorescent color.
- Thulium is also used in certain types of dosimeters, which measure a person’s exposure to radiation.
Did you know?
We ingest a small amount of thulium in our diet each year. It is not thought to serve any biological purpose. In certain forms thulium can be toxic to humans.