Element · Tm

Thulium

The rarest of the stable lanthanides, whose main job is to make X-rays without a power supply.

Thulium is the least abundant of the lanthanides that have stable isotopes, and for most of its history that scarcity meant it had no use at all — the chemistry was known long before there was enough of it to do anything with.

Irradiated in a reactor it becomes an isotope that emits X-rays, and a small sealed source of it makes a portable radiography unit that needs no electricity. That is a genuine advantage in a pipeline trench or on a ship's hull.

Uses

Portable X-ray sources for inspecting welds and castings are the established use, valued for working where no power is available.

Thulium-doped fibre lasers emit at a wavelength strongly absorbed by water, like holmium's, and are used in surgery and in laser rangefinders that need a wavelength safe for the eye.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is produced by

Rare earth separation — process · a heavy rare earth; the separation is the same cascade, run longer because the differences are smaller

is found in

Yttrium aluminium garnet — compound · for a wavelength close to holmium's, in surgical and lidar use

Sources

Material World
Our own writing
Wikidata
Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
PubChem
US National Library of Medicine · Mixed — aggregated third-party content, rights retained by depositors

Where it comes from, and what it becomes

Follow Thulium back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

Thulium → is produced by (a heavy rare earth; the separation is the same cascade, run longer because the differences are smaller) → Rare earth separation → takes as input (the principal ore of the light rare earths, carrying all of them together) → Bastnäsite
Thulium → is produced by (a heavy rare earth; the separation is the same cascade, run longer because the differences are smaller) → Rare earth separation → takes as input (the other feed alongside bastnäsite, bringing thorium into the residues with it) → Monazite
Thulium → is produced by (a heavy rare earth; the separation is the same cascade, run longer because the differences are smaller) → Rare earth separation → takes as input (the heavy rare earth feed, where monazite and bastnäsite bring the light ones) → Xenotime