Terbium was discovered by Carl Gustaf Mosander in 1843, when studying the ore Yttira. Terbium is a malleable and ductile metal and prefers to exist as a +3 ion. The ion emits a strong green luminescence when excited. Due to its luminescence it is used in colour phosphors in lighting. It is also used in euro bank notes to prevent forgeries. Due to its magnetism it is also used in the electric motors of hybrid cars. It is not found in free nature but found in minerals. It is a solid metal at room temperature with a melting point of 1356°c and a boiling point of 3230°c.
It is used in modest amounts in special lasers and solid-state devices.
Found with other rare earths in monazite sand, which typically contain 0.03% terbium. Other sources are xenotime and euxenite, both of which are oxide mixtures that can contain up to 1% terbium.