Solvent extraction dominates rare earth separation globally, with China controlling 90%+ of refining. Learn why Western challengers are rebuilding—not
Element Profile
Thulium
Symbol
Tm
Atomic number
69
Group
Heavy rare earth
Properties
Density
9.32 g/cm³
Melting point
1545 °C
Boiling point
1950 °C
Crustal abundance
0.52 ppm
Supply Risk
Supply risk
Medium
Geological scarcity
Extreme
Primary economic driver
Medical lasers and portable X-ray sources
Overview
About Thulium
Thulium (Tm, atomic number 69) is a heavy rare earth metal and, by U.S. Geological Survey figures, the scarcest of the rare earths found in nature in measurable amounts. Its best-known jobs are medical: a reactor-made thulium isotope powers small portable X-ray sources, and thulium lasers cut soft tissue and break up kidney stones. Demand is small. China added thulium to its export-control list in October 2025, then suspended the rule in November 2025 before it took effect.
What thulium is
Thulium is a bright, silvery-gray lanthanide and one of the heavy rare earth elements. Los Alamos National Laboratory describes it as soft enough to cut with a knife. It tarnishes slowly in air and reacts with water. Its average crustal abundance is 0.52 parts per million, the lowest of the rare earths listed in USGS Professional Paper 1802-O. That table leaves out promethium, which is extremely rare in nature.
The physical properties listed on this page are from the Royal Society of Chemistry periodic table.
Discovery and name
Swedish chemist Per Teodor Cleve discovered thulium at Uppsala University in 1879. He found it as an impurity in a sample of erbium oxide, known as erbia. Cleve named it after Thule, an ancient name for Scandinavia, according to the RSC. Los Alamos reports that American chemist Theodore William Richards obtained pure thulium in 1911 after recrystallizing thulium bromate 15,000 times.
Portable X-ray sources start in a nuclear reactor
Natural thulium consists of a single stable isotope, thulium-169. Irradiating it in a nuclear reactor turns it into thulium-170. Thulium-170 has a half-life of 128 days and gives off X-rays as it decays. A small "button" of this isotope is used to make lightweight, portable X-ray machines for medical use, according to the RSC. The RSC notes these sources have also turned up in dental equipment and in engineering crack detection. The device needs no electron beam, because the radiation comes from the isotope itself.
Thulium is sometimes described as a reactor neutron absorber or shielding material, but REEx found no authoritative source for either use.
Why surgeons use thulium lasers
Thulium-doped yttrium aluminum garnet, a synthetic crystal made with yttrium, is used in surgical lasers, according to Los Alamos. The RSC says these lasers work at a wavelength of about 2,000 nanometers, which suits laser surgery.
A newer design, the thulium fiber laser, uses thulium-doped silica fiber instead of a crystal. It works at 1,940 nanometers, close to a water absorption peak at 1,910 nanometers, according to a 2022 systematic review in Frontiers in Urology. The review describes its superpulsed mode as effective on kidney stones and its quasi-continuous mode as suited to cutting soft tissue. It found the laser comparable to standard surgery for removing enlarged prostate tissue.
Other uses
- Lamps. Thulium iodide has been used to add a bluish-green color to lamps (LANL).
- Banknote security. Los Alamos says euro banknotes contain thulium, which glows blue under ultraviolet light.
- Specialty optical fiber. Thulium is one of the rare earths doped into optical fiber for mid-infrared, surgical and sensing uses, REEx reported in July 2026.
- Superconductor research. Korean researchers grew superconducting thin films of a thulium-barium-copper oxide in a 2007 study. REEx found no commercial use.
Where thulium comes from
Thulium is recovered as a byproduct. It comes out of ore mined for the more common rare earths, mainly monazite and bastnaesite (RSC, LANL). Heavy rare earths are also enriched in ion-adsorption clays, according to USGS. It is separated from its neighbors by ion exchange and solvent extraction (RSC).
The RSC, using British Geological Survey data, lists China as the top producer, with 97% of output, followed by Russia and Malaysia. A 2018 review in the Journal of Sustainable Metallurgy found that thulium has no large-volume uses and that no production data exist for it as a single element. A 2015 paper by the same research group reported that thulium was produced in excess of demand and stockpiled.
China's export controls (as of October 2026)
Thulium was not among the seven rare earths China placed under export licensing in April 2025 (USGS). On October 9, 2025, China's Ministry of Commerce added thulium, holmium, erbium, europium and ytterbium in Announcement No. 57, according to Pillsbury. On November 7, 2025, China suspended that rule under MOFCOM Announcement No. 70. The rule had not yet taken effect. The suspension was set to end on November 10, 2026. As of early October 2026, China had not announced a formal extension.
An October 2025 IEA analysis put China's share at about 91% of separation and refining of the magnet rare earths. That estimate does not cover thulium.
Supply outside China (as of October 2026)
Lynas Rare Earths' October 2025 plan for a heavy rare earth plant in Malaysia named six products and four possible additions, according to its ASX announcement. Thulium was on neither list. REEx reported in September 2026 that Western strategy centers on NdPr, dysprosium and terbium, leaving thulium and other minor heavies in a blind spot.
Recycling
USGS reported that small quantities of heavy rare earths were recovered from permanent magnets in 2025, a use thulium does not have. REEx found no source describing commercial thulium recycling.
Why the price is hard to see
The USGS heavy rare earths summary publishes average prices for several heavy rare earth oxides but none for thulium. REEx's July 2026 reporting found that the thulium market was small and opaque. It also found that prices were often negotiated privately and Western buyers leaned on Chinese price agencies such as Asian Metal and Shanghai Metals Market.
What drives thulium demand and supply
Demand comes from medical lasers, portable X-ray sources and specialty optics, all of which use small amounts. Supply depends on mining for other rare earths and on separation in China. Supply also depends on Chinese export policy, including the controls announced in October 2025.
Frequently asked questions
What is thulium used for?
Its main uses are medical. A reactor-made isotope, thulium-170, powers portable X-ray sources, and thulium-doped lasers are used in surgery and to break up kidney stones. Smaller uses include lamps, specialty optical fiber and euro banknote security features.
How does thulium make a portable X-ray source?
Natural thulium-169 is irradiated in a nuclear reactor, which turns it into thulium-170. That isotope gives off X-rays as it decays, so a small button of it can serve as an X-ray source without an electrical tube.
Why do surgeons use thulium lasers?
Thulium lasers work at wavelengths near 2,000 nanometers, which water absorbs strongly. Thulium fiber lasers are used to break up kidney stones, cut soft tissue and remove enlarged prostate tissue.
Does China restrict thulium exports?
China added thulium to its export-control list on October 9, 2025, under Announcement No. 57. It suspended that rule on November 7, 2025, before it took effect. The suspension was set to end on November 10, 2026, and China had not announced a formal extension as of early October 2026.
Is thulium the rarest rare earth?
Among the rare earths that occur in nature in measurable amounts, thulium has the lowest average crustal abundance in U.S. Geological Survey data, at 0.52 parts per million. Promethium is rarer still but barely occurs in nature at all.
Primary Uses
- Thulium fiber and Tm:YAG surgical lasers (kidney stones, soft tissue, prostate)
- Portable X-ray sources (thulium-170)
- Lamps (thulium iodide)
- Specialty optical fiber dopant
- Euro banknote security features
Producing Projects
Companies
Found in Products
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