Even tough Thulium is rare as well,
it is less rare than gold in the continental shell.
One of the Lanthanides, a greay metal,
in ultraviolet light, a difference you can tell.

Per Teodor Cleve could measure its spectrum,
but finding turned out a big tantrum.
Almost twenty years later to German scientists,
Bommer and Klemm could add it to the elements list.

Hiding in Erbium and Ytterbium nearly to good,
Thulium only as minor part in rare earth ore include.
The seperation is after a proper oxidation,
a reduction and a sublimation.

Expensive but still with a unique use,
Thulium contains in secret a truth.
If enlighted with ultraviolet light,
its shine gets blue and bright.

Therefore on Euro notes, the metal stripe,
should do this trick very right,
Otherwise it is fake,
a good prove to take.

Another unique application,
is its ability to help measuring low dosage radiation.
So it protects peoply in radiochemistry sector,
with a Thulium dosimeter detector.

It is doped here and there enhancing some material,
some uses after all,
This is Thulium., a metal, a lanthanoide,
with some purpose, but no essential need.