Thulium Tm

spore: profile
id: thulium
spore_version: 0.2
family: rare-earth-metals
name: Thulium
abbreviation: Tm
role: 2 µm laser gain medium and dopant, and the Tm-170 portable X-ray source
category: metals
type: heavy-metals
summary: |
  Thulium is the element Tm (atomic number 69), a silvery-grey rare-earth metal with a hexagonal close-packed structure, a density of 9.321 g/cm3 at 20 °C and a melting point of 1545 °C. It is the least abundant of the rare-earth metals, at about 0.5 mg/kg in the Earth's crust. It is mined mainly from ion-adsorption clays in southern China and from monazite, and the metal is made by reducing its oxide with lanthanum or by calcium reduction in a closed container. Its main technical uses are as a dopant for lasers near 2 µm, which are eye-safer than 1 µm lasers, and as the Tm-170 isotope in portable X-ray sources. The metal tarnishes in air, reacts with water and dissolves in acid to release hydrogen, and its fine dust is flammable, so it needs dry, inert handling.
best_for: Thulium-doped 2 µm lasers (Tm:YAG and Tm fibre lasers) and the Tm-170 portable X-ray source (Goodfellow, Wikipedia)
weakest_at: Fine dust and chips that ignite, hydrogen release on contact with water or acid, and stiffness and strength figures that differ between sources (Ames SDS, Wikipedia, Goodfellow, WebElements)
identity:
  formula: Tm (element, atomic number 69); unalloyed metal, sold by Goodfellow in 99% (2N) and 99.7% (2N7) grades
  cas: 7440-30-4
  source: goodfellow-tm
  where: Identifiers section, CAS 7440-30-4; the same CAS is printed in the Wikipedia infobox
tags:
  environments: []
  applications:
    - optics-and-cameras
    - structures
properties:
  - benchmark: density
    label: Density, thulium
    value: 9.321
    unit: g/cm3
    scope: material
    conditions:
      temperature: 20 °C
      purity: not stated on the page
    method: Value printed in the supplier property table
    status: ground
    source: goodfellow-tm
    where: General Properties table, row Density (20 °C) 9.321 g/cm³
  - benchmark: density
    label: Density, thulium
    value: 9.32
    unit: g/cm3
    scope: material
    conditions:
      temperature: 20 °C
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-tm
    where: Infobox, Physical properties, row Density 9.320 g/cm3 at 20° C
  - benchmark: melting_point
    label: Melting point, thulium
    value: 1545
    unit: °C
    scope: material
    conditions:
      pressure: not stated
      purity: not stated on the page
    method: Value printed in the supplier property table
    status: ground
    source: goodfellow-tm
    where: General Properties table, row Melting Point 1,545 °C (1,818 K)
  - benchmark: melting_point
    label: Melting point, thulium
    value: 1545
    unit: °C
    scope: material
    conditions:
      pressure: not stated
      unit_in_source: 1818 K (1545 °C, 2813 °F)
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-tm
    where: Infobox, Physical properties, row Melting point 1818 K (1545 °C, 2813 °F)
  - benchmark: boiling_point
    label: Boiling point, thulium
    value: 1950
    unit: °C
    scope: material
    conditions:
      pressure: not stated
    method: Value printed in the supplier property table
    status: ground
    note: Wikipedia gives the same 1950 °C. A search snippet for an AK Scientific foil listing gave 1727 °C, which was not read on a page and is not entered.
    source: goodfellow-tm
    where: General Properties table, row Boiling Point 1,950 °C
  - benchmark: boiling_point
    label: Boiling point, thulium
    value: 1950
    unit: °C
    scope: material
    conditions:
      pressure: not stated
      unit_in_source: 2223 K (1950 °C, 3542 °F)
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-tm
    where: Infobox, Physical properties, row Boiling point 2223 K (1950 °C, 3542 °F)
  - benchmark: specific_heat
    label: Specific heat capacity, thulium
    value: 160.007
    unit: J/(kg·K)
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-tm
    where: Infobox, Physical properties, row Specific heat capacity 160.007 J/(kg·K) (no temperature given)
  - benchmark: thermal_conductivity
    label: Thermal conductivity, thulium
    value: 17
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: not stated on the page
      purity: not stated on the page
    method: Value printed in the supplier property table
    status: ground
    source: goodfellow-tm
    where: General Properties table, row Thermal Conductivity 17.0 W/m·K
  - benchmark: thermal_conductivity
    label: Thermal conductivity, thulium
    value: 16.9
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-tm
    where: Infobox, Other properties, row Thermal conductivity 16.9 W/(m⋅K)
  - benchmark: cte
    label: Coefficient of linear thermal expansion, thulium
    value: 13.3
    unit: ppm/K
    scope: material
    conditions:
      temperature: not stated on the page
      unit_in_source: 13.3 × 10-6 K-1
    method: Value printed in the WebElements property table
    status: ground
    source: webelements-tm
    where: Heat and conduction table, row Coefficient of linear thermal expansion 13.3 × 10-6 K-1
  - benchmark: cte
    label: Thermal expansion, thulium polycrystal
    value: 13.3
    unit: µm/(m·K)
    scope: material
    conditions:
      temperature: room temperature
      form: polycrystalline
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-tm
    where: Infobox, Other properties, row Thermal expansion poly 13.3 µm/(m⋅K) at r.t.
  - benchmark: elastic_modulus
    label: Young's modulus, thulium
    value: 74
    unit: GPa
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-tm
    where: Infobox, Other properties, row Young's modulus 74.0 GPa
  - benchmark: elastic_modulus
    label: Young's modulus, thulium
    value: 74
    unit: GPa
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on the WebElements physical-properties page
    status: ground
    source: webelements-tm
    where: Elastic properties, row Young's modulus 74 GPa
  - benchmark: elastic_modulus
    label: Tensile modulus, thulium (as supplied, annealed)
    value: 56
    unit: GPa
    scope: material
    conditions:
      temper: not stated on the page (hardness is given as annealed)
      temperature: not stated on the page
    method: Value printed in the supplier property table
    status: ground
    note: This is 18 GPa below the WebElements and Wikipedia values, so the sources disagree. All three are entered with their conditions.
    source: goodfellow-tm
    where: Mechanical Properties table, row Young's Modulus 56 GPa
  - benchmark: shear_modulus
    label: Rigidity (shear) modulus, thulium
    value: 31
    unit: GPa
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on the WebElements physical-properties page
    status: ground
    source: webelements-tm
    where: Elastic properties, row Rigidity modulus 31 GPa
  - benchmark: shear_modulus
    label: Shear modulus, thulium
    value: 30.5
    unit: GPa
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-tm
    where: Infobox, Other properties, row Shear modulus 30.5 GPa
  - benchmark: bulk_modulus
    label: Bulk modulus, thulium
    value: 45
    unit: GPa
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on the WebElements physical-properties page
    status: ground
    source: webelements-tm
    where: Elastic properties, row Bulk modulus 45 GPa
  - benchmark: bulk_modulus
    label: Bulk modulus, thulium
    value: 44.5
    unit: GPa
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-tm
    where: Infobox, Other properties, row Bulk modulus 44.5 GPa
  - benchmark: poissons_ratio
    label: Poisson's ratio, thulium
    value: 0.213
    unit: '-'
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-tm
    where: Infobox, Other properties, row Poisson ratio 0.213
  - benchmark: poissons_ratio
    label: Poisson's ratio, thulium (as supplied, annealed)
    value: 0.23
    unit: '-'
    scope: material
    conditions:
      temper: annealed (per the hardness row)
      temperature: not stated on the page
    method: Value printed in the supplier property table
    status: ground
    source: goodfellow-tm
    where: Mechanical Properties table, row Poisson's Ratio 0.23
  - benchmark: vickers_hardness
    label: Vickers hardness, thulium
    value: 520
    unit: MPa
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on the WebElements physical-properties page, given as MN m-2 (equal to MPa)
    status: ground
    note: No canonical name exists for hardness, so vickers_hardness is a new name and is listed in gaps.
    source: webelements-tm
    where: Hardnesses, row Vickers hardness 520 MN m-2
  - benchmark: vickers_hardness
    label: Vickers hardness range, thulium
    value: 470
    value_high: 650
    unit: MPa
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Range printed in the Wikipedia infobox
    status: ground
    note: Wikipedia gives a range with no test conditions. vickers_hardness is a new name and is listed in gaps.
    source: wikipedia-tm
    where: Infobox, Other properties, row Vickers hardness 470–650 MPa
  - benchmark: brinell_hardness
    label: Brinell hardness, thulium
    value: 471
    unit: MPa
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on the WebElements physical-properties page, given as MN m-2 (equal to MPa)
    status: ground
    note: No canonical name exists for Brinell hardness, so brinell_hardness is a new name and is listed in gaps.
    source: webelements-tm
    where: Hardnesses, row Brinell hardness 471 MN m-2
  - benchmark: brinell_hardness
    label: Brinell hardness range, thulium
    value: 470
    value_high: 900
    unit: MPa
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Range printed in the Wikipedia infobox
    status: ground
    note: Wikipedia gives a range with no test conditions. brinell_hardness is a new name and is listed in gaps.
    source: wikipedia-tm
    where: Infobox, Other properties, row Brinell hardness 470–900 MPa
  - benchmark: electrical_resistivity
    label: Electrical resistivity, thulium (as supplied)
    value: 142
    unit: nΩ·m
    scope: material
    conditions:
      temperature: 20 °C
      purity: not stated on the page
    method: Value printed in the supplier property table
    status: ground
    note: The Wikipedia value is about 4.8 times this one, so the sources disagree. Both are entered with their conditions.
    source: goodfellow-tm
    where: General Properties table, row Electrical Resistivity 142 nΩ·m (20 °C)
  - benchmark: electrical_resistivity
    label: Electrical resistivity, thulium polycrystal
    value: 676
    unit: nΩ·m
    scope: material
    conditions:
      temperature: room temperature
      form: polycrystalline
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-tm
    where: Infobox, Other properties, row Electrical resistivity poly 676 nΩ⋅m at r.t.
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, thulium (as supplied, annealed)
    value: 210
    unit: MPa
    scope: material
    conditions:
      temper: not stated on the page (hardness is given as annealed)
      purity: not stated on the page
      temperature: not stated on the page
    method: Value printed in the supplier property table
    status: ground
    source: goodfellow-tm
    where: Mechanical Properties table, row Tensile Strength 210 MPa
  - benchmark: neel_temperature
    label: Antiferromagnetic transition, thulium
    value: 56
    unit: K
    scope: material
    conditions:
      transition: antiferromagnetic below this temperature
      pressure: not stated
    method: Value printed in the supplier notes column
    status: ground
    note: The Wikipedia text gives ferromagnetic below 32 K, antiferromagnetic from 32 to 56 K, and paramagnetic above 56 K. neel_temperature is a new name and is listed in gaps.
    source: goodfellow-tm
    where: Notes column, magnetic note (antiferromagnetic below 56 K)
corrosion:
  - environment: Dry or moist air at room temperature
    headline: Thulium tarnishes slowly in air at room temperature.
    effect: Wikipedia says thulium tarnishes slowly in air, and Goodfellow rates its corrosion resistance as moderate and more air-stable than the light lanthanides. The surface oxide is Tm2O3, which forms in air.
    rating: low
    conditions:
      temperature: room temperature
      atmosphere: air, humidity not stated
    source: wikipedia-tm
    where: Chemical properties section, air; Goodfellow Chemical Properties table, row Corrosion Resistance and row Surface Oxide
  - environment: Air and moisture, handled as a reactive solid
    headline: The Ames SDS calls thulium air and moisture sensitive and says to store it under argon or mineral oil.
    effect: The Ames Laboratory SDS (revised 2016) lists thulium as air and moisture sensitive, with air and moisture as incompatible materials. It says to protect the metal from moisture and store it under argon or mineral oil in a cool, dry area.
    rating: moderate
    conditions:
      atmosphere: air and moisture
      temperature: not stated
    source: ames-tm-sds
    where: Section 7, Handling and Storage; Section 10, Incompatible Materials
  - environment: Heating in air
    headline: Thulium burns in air at about 150 °C.
    effect: Wikipedia says the metal burns at about 150 °C to form thulium(III) oxide, Tm2O3. The Ames SDS says thulium gives off oxide fumes in a fire.
    rating: moderate
    conditions:
      temperature: about 150 °C
      atmosphere: air
    source: wikipedia-tm
    where: Chemical properties section, air; Ames SDS Section 5, Specific Hazards
  - environment: Cold and hot water
    headline: Thulium reacts slowly with cold water and more quickly with hot water.
    effect: Wikipedia says thulium reacts slowly with cold water and more quickly with hot water to form thulium hydroxide. The Ames SDS says that under fire conditions the metal reacts with water to release flammable hydrogen gas.
    rating: moderate
    conditions:
      temperature: cold and hot water
      form: metal
    source: wikipedia-tm
    where: Chemical properties section, water; Ames SDS Section 10
  - environment: Dilute acids
    headline: Thulium dissolves readily in dilute acid and releases hydrogen.
    effect: Wikipedia says thulium dissolves readily in dilute sulfuric acid. The Ames SDS says contact with acids may evolve hydrogen gas.
    rating: severe
    conditions:
      acid: dilute sulfuric acid, and acids in general per the SDS
      temperature: not stated
    source: wikipedia-tm
    where: Chemical properties section, acid; Ames SDS Section 10, Possibility of Hazardous Reactions
  - environment: Halogens, oxidizers and acid chlorides
    headline: Thulium is incompatible with halogens, oxidizing agents and acid chlorides.
    effect: The Ames SDS lists acids, acid chlorides, oxidizing agents and halogens as incompatible materials for the metal. It gives no test result or rate for these reactions.
    rating: severe
    conditions:
      atmosphere: halogen vapour or oxidizing agent
      temperature: not stated
    source: ames-tm-sds
    where: Section 10, Stability and Reactivity, Incompatible Materials
risks:
  hazards:
    - text: 'PubChem GHS summary (ECHA C&L notifications, 50 company reports): H228 flammable solid in 94 % of notifications, H319 in 80 % and H335 in 80 %. Signal word Danger. 3 of 50 reports say the substance does not meet GHS criteria.'
      ghs:
        - H228
        - H319
        - H335
      source: pubchem-tm
      where: Safety and Hazards, Hazards Identification, GHS Classification
    - text: 'Ames Laboratory SDS for thulium pieces, ingot, rod, foil, sheet and target (revised January 26, 2016): classified under CLP as a flammable solid (H228) and as a substance which in contact with water releases flammable gases which may ignite spontaneously (H260). Signal word Danger.'
      ghs:
        - H228
        - H260
      source: ames-tm-sds
      where: Section 2, Hazards Identification (H228, H260, Danger)
    - text: Wikipedia says soluble thulium salts are mildly toxic, insoluble salts are essentially nontoxic, and the metal has low to moderate toxicity. Injected thulium can damage the liver and spleen.
      ghs: []
      source: wikipedia-tm
      where: Biological role section, toxicity paragraph
    - text: The Ames SDS says solid thulium presents few health hazards under normal handling, but grinding, melting or welding may create dusts or fumes that can be inhaled. Its OSHA PEL and ACGIH TLV are both 'no exposure limit established'.
      ghs: []
      source: ames-tm-sds
      where: Section 4, General Measures; Section 8, Exposure Limits
  failure_risks:
    - mode: Fire in dust and fines
      trigger: Thulium dust or fines exposed to heat, spark or flame
      consequence: The Ames SDS says the metal is flammable in dust form when exposed to heat, spark or flame, and Wikipedia says thulium dust can cause explosions and fires. Fire-fighting with water is not allowed.
      severity: high
      source: ames-tm-sds
      where: Section 5, Specific Hazards Arising from the Material; Section 5, Unsuitable Extinguishing Media
    - mode: Hydrogen release on contact with water or acid
      trigger: Metal in contact with water (especially hot or in a fire) or with acids
      consequence: The Ames SDS says the metal may react with water under fire conditions to release flammable hydrogen, and that contact with acids may evolve hydrogen gas. Wikipedia says the reaction is slow in cold water and quicker in hot water.
      severity: high
      source: ames-tm-sds
      where: Section 10, Possibility of Hazardous Reactions; Wikipedia Chemical properties, water
    - mode: Oxidation in air and moisture
      trigger: Metal exposed to air or moisture
      consequence: The Ames SDS calls thulium air and moisture sensitive. Wikipedia says it tarnishes slowly and burns at about 150 °C to Tm2O3, so the surface and fines change over time.
      severity: moderate
      source: ames-tm-sds
      where: Section 7, Handling and Storage; Wikipedia Chemical properties, air
    - mode: Reaction with halogens, oxidizers or acids
      trigger: Contact with halogens, oxidizing agents, acid chlorides or acids
      consequence: The Ames SDS lists these as incompatible materials, which can cause a reaction on contact.
      severity: moderate
      source: ames-tm-sds
      where: Section 10, Incompatible Materials
  side_effects:
    - text: Tm-170 is radioactive (half-life 128.6 days, beta-minus decay) and emits soft X-rays at about 7 to 84 keV, so the sealed portable sources need radiation controls.
      affects: Operators and nearby personnel for portable Tm-170 sources
      source: wikipedia-tm
      where: Isotopes section, Tm-170; Applications, X-ray sources
  handling:
    - text: Store the metal in tightly closed containers under argon or mineral oil, in a cool, dry area, and protect it from water and moisture (Ames SDS, Section 7).
      source: ames-tm-sds
      where: Section 7, Conditions for Safe Storage, Including Any Incompatibilities
    - text: Handle the metal under inert gas and protect it from moisture (Ames SDS precautionary statements P231 and P232).
      source: ames-tm-sds
      where: Section 2, Precautionary Statements
    - text: Use a Class D dry powder extinguishing agent in a fire, and do not use water (Ames SDS, Section 5).
      source: ames-tm-sds
      where: Section 5, Extinguishing Media; Unsuitable Extinguishing Media
    - text: Use local exhaust or other engineering controls for dust and fume, and a NIOSH-approved dust respirator if exposure limits are exceeded (Ames SDS, Section 8).
      source: ames-tm-sds
      where: Section 8, Engineering Controls and Respiratory Protection
  mitigations: []
uses:
  - application: optics-and-cameras
    device: Tm:YAG and Tm fibre lasers at about 2 µm, used in surgery and in industrial processing
    example: Wikipedia says Ho:Cr:Tm:YAG lases at 2080 nm and single-element Tm:YAG at 2010 nm, and it lists military, medical and meteorological uses. Goodfellow puts Tm:YAG and Tm:YLF surgical lasers at about 2,013 to 2,090 nm and Tm fibre lasers above 1 kW. The 2020 Materials review calls thulium- and holmium-doped fibre lasers the first choice for 2 µm and names lidar and gas sensing as applications.
    source: wikipedia-tm
    where: Applications, Lasers section; Goodfellow Overview; PMC7696405 Introduction
  - application: structures
    device: Tm-170 portable X-ray source for field radiography, such as pipe weld inspection
    example: Tm-170 has a half-life of 128.6 days and emits X-rays from about 7 to 84 keV. Goodfellow says it was the primary portable X-ray source for field radiography before miniature tubes displaced it, and that it remains in use in small-bore pipe weld inspection where electrical power is unavailable.
    source: goodfellow-tm
    where: Overview paragraph on 170Tm portable X-ray sources; Wikipedia Applications, X-ray sources
supply:
  - subject: Rare earths (thulium is not reported separately by USGS)
    abundance: 0.5 mg/kg in the Earth's crust (Wikipedia, Occurrence section); Goodfellow gives about 0.5 ppm
    producers:
      - country: China
        share_percent: 69.2
        year: 2025
      - country: United States
        share_percent: 13.1
        year: 2025
      - country: Australia
        share_percent: 7.4
        year: 2025
      - country: Burma
        share_percent: 5.6
        year: 2025
    critical_lists: []
    recycling: 'USGS: limited quantities of rare earths were recovered from batteries, permanent magnets and fluorescent lamps (group-level statement).'
    substitutes:
      - 'USGS: substitutes are available for many applications but generally are less effective (group-level statement).'
    source: usgs-ree-2026
    where: 'World Mine Production table, 2025 (world total 390,000 t; shares calculated from China 270,000, United States 51,000, Australia 29,000 and Burma 22,000). Reserves: China 44,000,000 t of more than 75,000,000 t world total. Recycling and Substitutes sections.'
  - subject: Thulium in Chinese export controls
    producers: []
    critical_lists: []
    recycling: ''
    substitutes: []
    source: usgs-ree-2026
    where: 'Events, Trends and Issues: in October 2025 China expanded its rare-earth export controls to include thulium; in November it suspended the October controls for one year. The April 2025 controls, which do not list thulium, remained in effect.'
  - subject: Rare-earth compounds and metals imported into the United States
    producers:
      - country: China
        share_percent: 71
        year: 2024
      - country: Malaysia
        share_percent: 13
        year: 2024
      - country: Japan
        share_percent: 5
        year: 2024
      - country: Estonia
        share_percent: 5
        year: 2024
    critical_lists: []
    recycling: ''
    substitutes: []
    source: usgs-ree-2026
    where: Import Sources (2021–24) paragraph, China 71%, Malaysia 13%, Japan 5%, Estonia 5%; the year column shows the end of the 2021 to 2024 range. Group-level figure for all rare-earth compounds and metals.
documents:
  - title: 'USGS Mineral Commodity Summaries 2026: Rare Earths'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf
    year: 2026
  - title: 'Wikipedia: Thulium'
    type: database
    url: https://en.wikipedia.org/wiki/Thulium
    year: 2026
  - title: PubChem compound record for thulium (CID 23961), including ECHA C&L Inventory classification
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/23961
    year: 2026
  - title: Thulium, high-purity rare-earth metal, 99% (2N) and 99.7% (2N7) grades (Goodfellow product page)
    type: datasheet
    url: https://www.goodfellow.com/usa/material/rare-earth-metals/thulium
  - title: 'WebElements: Thulium, physical properties (University of Sheffield)'
    type: datasheet
    url: https://winter.group.shef.ac.uk/webelements/thulium/physics.html
  - title: 'Safety data sheet: Thulium pieces, ingot, rod, foil, sheet and target, Ames Laboratory Materials Preparation Center (revised January 26, 2016)'
    type: sds
    url: https://www.ameslab.gov/sites/default/files/inline-files/69_Thulium_SDS.pdf
    year: 2016
  - title: Active Optical Fibers and Components for Fiber Lasers Emitting in the 2-µm Spectral Range (Materials, 2020, open access)
    type: paper
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC7696405
    year: 2020
  - title: 'NIST Atomic Weights and Isotopic Compositions: thulium (Tm, Z = 69)'
    type: database
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Tm
    year: 2026
gaps:
  - 'Thulium-specific production: USGS reports rare earths as one group, so the producer shares above are for all rare earths, not for thulium. Wikipedia says the principal source is ion-adsorption clays in southern China, where thulium is about 0.5 % of the rare-earth content, but gives no production tonnage for the metal.'
  - 'Critical-mineral listing: the USGS 2025 critical minerals list and the EU critical raw materials list were not opened for thulium, so critical_lists is empty. Heavy rare earths are a separate USGS chapter that was not read.'
  - 'Space flight of thulium: no flight, vacuum, radiation or thermal-cycling result for thulium metal was found in the sources read. The environments tag is left empty.'
  - Electrical resistivity disagrees by a factor of about 4.8 between Goodfellow (142 nΩ·m at 20 °C) and Wikipedia (676 nΩ·m at room temperature). WebElements prints 67.6 × 10-8 Ω m, which agrees with Wikipedia, but it is not entered as a row because the page does not print the value in the file's unit. Both entered rows keep their conditions.
  - Young's modulus disagrees between Goodfellow (56 GPa, as-supplied annealed disc) and WebElements and Wikipedia (74 to 74.0 GPa). All three are entered with their conditions.
  - 'Boiling point: a search snippet for an AK Scientific foil listing gave 1727 °C, which conflicts with the 1950 °C of Goodfellow and Wikipedia. It was not read on a fetched page and is not entered.'
  - Vickers and Brinell hardness are entered under the new names vickers_hardness and brinell_hardness, because the property file has no canonical name for them. Goodfellow prints the hardness as about 52 to 60 HB (annealed); the HB unit is not converted and that value is not entered.
  - The magnetic transition is entered under the new name neel_temperature. Wikipedia gives ferromagnetic below 32 K and antiferromagnetic from 32 to 56 K, and Goodfellow gives antiferromagnetic below 56 K. Only the 56 K figure is entered.
  - Tensile strength (210 MPa) is from Goodfellow, which prints no temper beyond annealed hardness and no purity for the figure. No cast, rolled or high-temperature strength data were found in an opened source.
  - Goodfellow prints an elongation at break of about 20 %. The figure is approximate, so it is not entered.
  - Corrosion data are qualitative (Wikipedia, Goodfellow and the Ames SDS). No measured weight-gain or corrosion-rate figure for thulium in air or water was found.
  - 'Hazard data: the PubChem notifications (H228, H319 and H335) and the Ames SDS (H228 and H260) differ, and the Ames SDS is a 2016 revision. The American Elements SDS was only seen in a search snippet and was not read. The form (pieces, foil or powder) matters and was not separated in every source.'
  - 'Access blocks: the Royal Society of Chemistry, American Elements and LANL periodic-table pages returned HTTP 403, and the PubChem web page returned a browser check. The PubChem REST record and the other sources were read in full.'
  - 'Goodfellow hardness and grade codes: the Goodfellow page lists two grades (99 % and 99.7 %) without product codes, and it gives no separate value per grade.'
  - 'No media: no image was fetched for thulium in this run.'
sources:
  usgs-ree-2026:
    title: 'Mineral Commodity Summaries 2026: Rare Earths (USGS)'
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-rare-earths.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  wikipedia-tm:
    title: Thulium (Wikipedia)
    url: https://en.wikipedia.org/wiki/Thulium
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  pubchem-tm:
    title: 'PubChem compound record: Thulium (CID 23961), including ECHA C&L Inventory classification'
    id: CAS 7440-30-4
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23961/JSON
    kind: database
    license: PubChem (NCBI), public domain; sections attributed to ECHA and others
  goodfellow-tm:
    title: Thulium, high-purity rare-earth metal (Goodfellow product page)
    url: https://www.goodfellow.com/usa/material/rare-earth-metals/thulium
    kind: datasheet
    license: supplier web page (cited, not reproduced)
  webelements-tm:
    title: 'WebElements: Thulium, physical properties (University of Sheffield)'
    url: https://winter.group.shef.ac.uk/webelements/thulium/physics.html
    kind: database
    license: WebElements, cited not reproduced
  ames-tm-sds:
    title: 'Safety Data Sheet: Thulium pieces, ingot, rod, foil, sheet and target (Ames Laboratory Materials Preparation Center, revised January 26, 2016)'
    url: https://www.ameslab.gov/sites/default/files/inline-files/69_Thulium_SDS.pdf
    year: 2016
    kind: datasheet
    license: supplier safety data sheet, cited not reproduced
  pmc-2um-fiber:
    title: Active Optical Fibers and Components for Fiber Lasers Emitting in the 2-µm Spectral Range (Materials 13, 5177, 2020)
    url: https://pmc.ncbi.nlm.nih.gov/articles/PMC7696405
    year: 2020
    kind: paper
    license: open access, cited not reproduced
  nist-tm-weight:
    title: 'NIST Atomic Weights and Isotopic Compositions: thulium'
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Tm
    year: 2026
    kind: database
    license: public domain (NIST)
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 28
  unreachable: 3
  caveats: 7
  note: 'Read by an AI assistant on 2026-10-26 from the pages and PDFs named in each entry. Unreachable: Royal Society of Chemistry, American Elements and LANL periodic-table pages (HTTP 403). Caveats: most physical values come from one supplier (Goodfellow), one encyclopedia (Wikipedia) and one lab page (WebElements); electrical resistivity and Young''s modulus disagree between sources; the hazard classes differ between PubChem and the 2016 Ames SDS; supply shares are for all rare earths, not thulium; the hardness and magnetic-transition names are new.'
story:
  risk_groups:
    - title: For people
      lead: The hazard is in the metal's form. Solid thulium presents few health hazards under normal handling, but its dust and fines are flammable, and soluble thulium salts are mildly toxic.
      level: 1
      verdict: Form-dependent
      points:
        - label: Dust and fines
          line: The Ames SDS says thulium is flammable in dust form when exposed to heat, spark or flame, and classifies it as a flammable solid (H228).
        - label: Water and acid
          line: The Ames SDS says the metal may release flammable hydrogen on contact with water under fire conditions and that acids may evolve hydrogen gas (H260).
        - label: Exposure limits
          line: Neither OSHA nor ACGIH has set an exposure limit for thulium (Ames SDS, Section 8). Wikipedia says soluble salts are mildly toxic and the metal has low to moderate toxicity.
        - label: Radiation from Tm-170
          line: The Tm-170 isotope used in portable X-ray sources is radioactive, with a half-life of 128.6 days (Wikipedia).
    - title: If it fails
      lead: 'The sources give four failure routes: fire in dust and fines, hydrogen release on contact with water or acid, oxidation in air and moisture, and reaction with halogens or oxidizers.'
      points:
        - label: Fire
          line: Use a Class D dry powder agent, and do not use water on the metal (Ames SDS).
        - label: Air and moisture
          line: Thulium tarnishes slowly in air and burns at about 150 °C to Tm2O3 (Wikipedia). The Ames SDS says it is air and moisture sensitive.
        - label: Halogens and oxidizers
          line: The Ames SDS lists halogens, oxidizing agents, acids and acid chlorides as incompatible with the metal.
    - title: Handling and storage
      points:
        - label: Keep it dry
          line: Store under argon or mineral oil in tightly closed containers in a cool, dry area, and protect it from water and moisture (Ames SDS, Section 7).
        - label: Dust control
          line: Use local exhaust or other engineering controls, and a NIOSH-approved dust respirator if exposure limits are exceeded (Ames SDS, Section 8).
  why: Thulium is a heavy rare-earth metal valued for the light it emits rather than for structure. Its ions lase near 2 µm when pumped, which suits Tm:YAG and Tm fibre lasers in surgery and industrial processing, and 2 µm is eye-safer than 1 µm Nd:YAG at equivalent power (Goodfellow). The Tm-170 isotope made by neutron irradiation has been used as a short-lived portable X-ray source. The metal itself is a reactive, dust-flammable solid, and no source reports thulium flown in space.
  uses:
    - where: Lasers at 2 µm
      line: Tm:YAG and Tm fibre lasers emit near 2 µm and are used in surgery, in industrial processing and in lidar and gas-sensing research (Wikipedia, Goodfellow, and the 2020 Materials review).
    - where: Portable X-ray sources
      line: Tm-170, made by neutron bombardment, emits soft X-rays for field radiography and pipe weld inspection where electrical power is unavailable (Goodfellow and Wikipedia).
  can_do:
    - label: Lase at 2 µm
      value: 2010 nm
      line: Single-element Tm:YAG lases at 2010 nm, and Ho:Cr:Tm:YAG at 2080 nm (Wikipedia).
    - label: Weight
      value: 9.321 g/cm3
      benchmark: density
      line: Density is 9.321 g/cm3 at 20 °C for the supplier grade (Goodfellow), and 9.320 g/cm3 at 20 °C in the Wikipedia infobox.
    - label: Melting
      value: 1545 °C
      benchmark: melting_point
      line: Melting point is 1545 °C (Goodfellow and Wikipedia).
    - label: Stiffness
      value: 74 GPa
      benchmark: elastic_modulus
      line: Young's modulus is 74.0 GPa (Wikipedia) and 74 GPa (WebElements). Goodfellow gives 56 GPa for an annealed disc.
    - label: Heat conduction
      value: 17.0 W/(m·K)
      benchmark: thermal_conductivity
      line: Thermal conductivity is 17.0 W/(m·K) (Goodfellow) and 16.9 W/(m·K) (Wikipedia).
  compare: Thulium is a dense rare-earth metal at 9.321 g/cm3, with a melting point of 1545 °C and a thermal conductivity of about 17 W/(m·K). Its Young's modulus is about 74 GPa in two sources, and 56 GPa in a third, so the stiffness figure is uncertain. Its laser and X-ray uses depend on the 2 µm emission and the Tm-170 decay, not on its bulk properties. The metal tarnishes in air and reacts with water, so it needs dry, inert handling. No comparison profile is carried in this file, so the rows below list thulium values only.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  recipe:
    line: Thulium is a single-element metal (Tm). Wikipedia says it is mined mainly from monazite (about 0.007 % thulium) and from ion-adsorption clays in southern China, where it is about 0.5 % of the rare-earth content. It is isolated by reducing its oxide with lanthanum metal, or by calcium reduction in a closed container. Goodfellow adds that thulium is extracted primarily from ion-adsorption clays and xenotime.
    parts:
      - name: Thulium
        symbol: Tm
        atoms: 1
        atomic_weight: 168.93422
        role: The whole material. Natural thulium is monoisotopic, its only natural isotope being stable (Goodfellow, PubChem). The atomic weight is from NIST.
  handling:
    - Store under argon or mineral oil in tightly closed containers, in a cool, dry area (Ames SDS, Section 7).
    - Handle under inert gas and protect from moisture (Ames SDS, precautionary statements P231 and P232).
    - Use Class D dry powder for a fire, and do not use water (Ames SDS, Section 5).
    - Use local exhaust for dust and fume, and a NIOSH-approved dust respirator if limits are exceeded (Ames SDS, Section 8).
  good_for:
    - 'Lasers near 2 µm: Tm:YAG at 2010 nm and Ho:Cr:Tm:YAG at 2080 nm (Wikipedia), used in surgery and industrial processing.'
    - 'Portable X-ray sources: Tm-170, with a half-life of 128.6 days, for field radiography (Wikipedia, Goodfellow).'
  watch_out:
    - Dust and fines are flammable, and water is not to be used on a fire (Ames SDS).
    - Water and acid release flammable hydrogen (Ames SDS). The metal tarnishes in air and burns at about 150 °C (Wikipedia).
    - 'Supply is concentrated: China produced about 69 % of world rare-earth mine output in 2025, and China added thulium to its October 2025 export controls, which it then suspended for one year (USGS).'
    - Most figures come from one supplier, one encyclopedia and one lab page. Electrical resistivity and Young's modulus differ between sources, and the Ames SDS is a 2016 revision.
  verdict: Thulium is a dense rare-earth metal, at 9.321 g/cm3 with a melting point of 1545 °C. Its value lies in 2 µm laser media and the short-lived Tm-170 X-ray source, not in structure. The metal needs dry, inert handling, because its dust is flammable and it releases hydrogen with water or acid.