Lanthanum La

spore: profile
id: lanthanum
spore_version: 0.2
family: rare-earth-metals
name: Lanthanum
abbreviation: La
role: optical-glass and battery-alloy rare-earth metal; LaB6 thermionic emitter in electric-propulsion cathodes
category: metals
type: heavy-metals
summary: |
  Lanthanum is the element La, a silvery rare-earth metal with a density of 6.145 g/cm3 at 20 °C (Wikipedia) and a melting point of 920 °C. It makes up 39 mg/kg of the Earth's crust (Wikipedia) and is mined together with the other rare earths, where China produced 270,000 of 390,000 t in 2025 (USGS). Its main uses are as lanthanum oxide in high-index optical glass and as an alloy component in nickel-metal-hydride battery anodes. The metal tarnishes in air within hours and reacts with water and acids to release flammable hydrogen, so it is classed as a flammable solid and is kept under argon. A NASA record describes lanthanum hexaboride (a compound, not the metal) as a thermionic emitter in Hall-thruster hollow cathodes.
best_for: Optical glass and camera-lens additive (lanthanum oxide, high refractive index), and LaB6 emitters in Hall-thruster cathodes (Wikipedia; NASA Tech Briefs 2010)
weakest_at: 'Handling: a flammable solid that tarnishes in air within hours and releases hydrogen with water and acids (ESPI, Lesker, Wikipedia)'
identity:
  formula: La (element); lanthanum metal, 100 % La in the Lesker and ESPI sheets
  cas: 7439-91-0
  source: pubchem-la
  where: Other Identifiers, CAS entry (PubChem CID 23926); CAS 7439-91-0 and EC number 231-099-0 are also printed in the ESPI SDS, Section 3
tags:
  applications:
    - optics-and-cameras
    - propulsion-and-tanks
    - batteries
properties:
  - benchmark: density
    label: Density, lanthanum at 20 °C (Wikipedia)
    value: 6.145
    unit: g/cm3
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: 6.145 g/cm3 (at 20 °C)
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-la
    where: Infobox, row Density (at 20 °C) 6.145 g/cm3
  - benchmark: density
    label: Density, lanthanum at 25 °C (PubChem experimental)
    value: 6.166
    unit: g/cm3
    scope: material
    conditions:
      temperature: 25 °C
    method: Experimental property printed in the PubChem record
    status: ground
    source: pubchem-la
    where: Chemical and Physical Properties, Experimental Properties, Density 6.166 @25 °C
  - benchmark: density
    label: Relative density, lanthanum solid (ESPI SDS)
    value: 6.17
    unit: g/cc
    scope: material
    conditions:
      temperature: 20 °C
      form: solid pieces, as sold for scientific research
    method: Value printed in the supplier safety data sheet
    status: ground
    source: espi-la-sds
    where: Section 9, Relative Density (Specific Gravity) 6.17 g/cc at 20 °C
  - benchmark: density
    label: Density of solid, lanthanum (WebElements)
    value: 6146
    unit: kg/m3
    scope: material
    conditions:
      temperature: not stated
    method: Value printed on the WebElements physical-properties page
    status: ground
    source: webelements-la
    where: Density properties, row Density (of solid) 6146 kg m-3
  - benchmark: melting_point
    label: Melting point, lanthanum (Wikipedia)
    value: 920
    unit: °C
    scope: material
    conditions:
      pressure: not stated
      unit_in_source: 1193 K (920 °C, 1688 °F)
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-la
    where: Infobox, row Melting point, 1193 K (920 °C, 1688 °F)
  - benchmark: melting_point
    label: Melting point, lanthanum (PubChem)
    value: 920
    unit: °C
    scope: material
    conditions:
      pressure: not stated
    method: Experimental property printed in the PubChem record
    status: ground
    source: pubchem-la
    where: Chemical and Physical Properties, Experimental Properties, Melting Point 920 °C
  - benchmark: melting_point
    label: Melting point, lanthanum solid (ESPI SDS)
    value: 918
    unit: °C
    scope: material
    conditions:
      form: solid
    method: Value printed in the supplier safety data sheet
    status: ground
    note: The sources give 918 to 921 °C. All are entered with their own source, and none has been averaged.
    source: espi-la-sds
    where: Section 9, Melting Point 918 °C
  - benchmark: melting_point
    label: Melting point, lanthanum metal (Lesker MSDS, 1991)
    value: 921
    unit: °C
    scope: material
    conditions:
      form: silver solid pieces or powder
    method: Value printed in the 1991 supplier safety data sheet
    status: ground
    source: lesker-la-msds
    where: Section III Physical Data, Melting Point (oC) 921oC
  - benchmark: boiling_point
    label: Boiling point, lanthanum (Wikipedia)
    value: 3464
    unit: °C
    scope: material
    conditions:
      pressure: not stated
      unit_in_source: 3737 K (3464 °C, 6267 °F)
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-la
    where: Infobox, row Boiling point, 3737 K (3464 °C, 6267 °F)
  - benchmark: boiling_point
    label: Boiling point, lanthanum (PubChem)
    value: 3464
    unit: °C
    scope: material
    conditions:
      pressure: 760 mmHg
    method: Experimental property printed in the PubChem record
    status: ground
    source: pubchem-la
    where: Chemical and Physical Properties, Experimental Properties, Boiling Point 3464 °C @760 mm Hg
  - benchmark: specific_heat
    label: Specific heat capacity, lanthanum (Wikipedia)
    value: 195.162
    unit: J/(kg·K)
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-la
    where: Infobox, row Specific heat capacity 195.162 J/(kg·K)
  - benchmark: thermal_conductivity
    label: Thermal conductivity, lanthanum (Wikipedia)
    value: 13.4
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: not stated in the infobox
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-la
    where: Infobox, row Thermal conductivity 13.4 W/(m⋅K)
  - benchmark: thermal_conductivity
    label: Thermal conductivity, lanthanum (WebElements)
    value: 13
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: not stated
    method: Value printed on the WebElements physical-properties page
    status: ground
    source: webelements-la
    where: Heat and conduction, row Thermal conductivity 13 W m-1 K-1
  - benchmark: cte
    label: Coefficient of thermal expansion, lanthanum (Wikipedia)
    value: 5.1
    unit: ppm/K
    scope: material
    conditions:
      temperature: 20 °C
      unit_in_source: 5.1×10−6/K (at 20 °C)
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-la
    where: Infobox, row Thermal expansion, 5.1×10−6/K (at 20 °C)
  - benchmark: elastic_modulus
    label: Young's modulus, lanthanum alpha form (Wikipedia)
    value: 36.6
    unit: GPa
    scope: material
    conditions:
      temperature: not stated in the infobox
      form: alpha form, double hexagonal close-packed (dhcp)
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-la
    where: Infobox, row Young's modulus, alpha form 36.6 GPa
  - benchmark: elastic_modulus
    label: Young's modulus, lanthanum (WebElements)
    value: 37
    unit: GPa
    scope: material
    conditions:
      temperature: not stated
    method: Value printed on the WebElements physical-properties page
    status: ground
    source: webelements-la
    where: Elastic properties, row Young's modulus 37 GPa
  - benchmark: shear_modulus
    label: Shear modulus, lanthanum alpha form (Wikipedia)
    value: 14.3
    unit: GPa
    scope: material
    conditions:
      temperature: not stated in the infobox
      form: alpha form, double hexagonal close-packed (dhcp)
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-la
    where: Infobox, row Shear modulus, alpha form 14.3 GPa
  - benchmark: shear_modulus
    label: Rigidity (shear) modulus, lanthanum (WebElements)
    value: 14
    unit: GPa
    scope: material
    conditions:
      temperature: not stated
    method: Value printed on the WebElements physical-properties page
    status: ground
    source: webelements-la
    where: Elastic properties, row Rigidity modulus 14 GPa
  - benchmark: bulk_modulus
    label: Bulk modulus, lanthanum alpha form (Wikipedia)
    value: 27.9
    unit: GPa
    scope: material
    conditions:
      temperature: not stated in the infobox
      form: alpha form, double hexagonal close-packed (dhcp)
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-la
    where: Infobox, row Bulk modulus, alpha form 27.9 GPa
  - benchmark: bulk_modulus
    label: Bulk modulus, lanthanum (WebElements)
    value: 28
    unit: GPa
    scope: material
    conditions:
      temperature: not stated
    method: Value printed on the WebElements physical-properties page
    status: ground
    source: webelements-la
    where: Elastic properties, row Bulk modulus 28 GPa
  - benchmark: poissons_ratio
    label: Poisson's ratio, lanthanum alpha form (Wikipedia)
    value: 0.28
    unit: '-'
    scope: material
    conditions:
      temperature: not stated in the infobox
      form: alpha form, double hexagonal close-packed (dhcp)
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-la
    where: Infobox, row Poisson ratio, alpha form 0.280
  - benchmark: poissons_ratio
    label: Poisson's ratio, lanthanum (WebElements)
    value: 0.28
    unit: '-'
    scope: material
    conditions:
      temperature: not stated
    method: Value printed on the WebElements physical-properties page
    status: ground
    source: webelements-la
    where: Elastic properties, row Poisson's ratio 0.28 (no units)
  - benchmark: brinell_hardness
    label: Brinell hardness, lanthanum (WebElements)
    value: 363
    unit: MPa
    scope: material
    conditions:
      temperature: not stated
      unit_in_source: 363 MN m-2
    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 in the property file, so brinell_hardness is a new name and is listed in gaps.
    source: webelements-la
    where: Hardnesses, row Brinell hardness 363 MN m-2
  - benchmark: brinell_hardness
    label: Brinell hardness range, lanthanum (Wikipedia)
    value: 350
    value_high: 400
    bound: range
    unit: MPa
    scope: material
    conditions:
      temperature: not stated in the infobox
      note_on_range: the infobox gives a range, not a single test value
    method: Range printed in the Wikipedia infobox
    status: ground
    note: No canonical name exists for hardness, so brinell_hardness is a new name and is listed in gaps. The range is given by Wikipedia without test conditions.
    source: wikipedia-la
    where: Infobox, row Brinell hardness 350–400 MPa
  - benchmark: vickers_hardness
    label: Vickers hardness, lanthanum (WebElements)
    value: 491
    unit: MPa
    scope: material
    conditions:
      temperature: not stated
      unit_in_source: 491 MN m-2
    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-la
    where: Hardnesses, row Vickers hardness 491 MN m-2
  - benchmark: electrical_resistivity
    label: Electrical resistivity, lanthanum alpha polycrystalline form (Wikipedia)
    value: 615
    unit: nΩ·m
    scope: material
    conditions:
      temperature: room temperature (printed as r.t.)
      form: alpha, polycrystalline
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wikipedia-la
    where: Infobox, row Electrical resistivity, alpha poly 615 nΩ⋅m (at r.t.)
corrosion:
  - environment: Air at room temperature
    headline: Lanthanum tarnishes quite rapidly in air and turns completely dark within several hours.
    effect: Wikipedia says lanthanum tarnishes quite rapidly in air, turning completely dark after several hours. The Ames and ESPI sheets list exposure to moist air or water as a condition to avoid, and say the metal should be kept under argon.
    rating: severe
    conditions:
      atmosphere: air
      temperature: room temperature
    source: wikipedia-la
    where: Characteristics, Chemical; the sentence on air reactivity
  - environment: Water
    headline: Lanthanum reacts slowly with water to form lanthanum hydroxide, and releases hydrogen when water is present in a fire.
    effect: Wikipedia says the metal reacts slowly with water to form lanthanum(III) hydroxide. The ESPI SDS says it may react with water under fire conditions and release flammable hydrogen gas, and the Lesker MSDS says it can react with water to form explosive H2.
    rating: severe
    conditions:
      temperature: not stated for the slow reaction; hydrogen release is stated under fire conditions
    source: espi-la-sds
    where: Section 5 Specific Hazards; Section 10 Possibility of Hazardous Reactions; Lesker MSDS Section VII
  - environment: Dilute and strong acids
    headline: Lanthanum reacts vigorously with acids and releases flammable hydrogen.
    effect: The ESPI SDS says the metal reacts vigorously with acids, releasing flammable hydrogen gas, and lists strong acids and acid chlorides as incompatible. The Lesker MSDS also lists strong acids as incompatible.
    rating: severe
    conditions:
      acid: strong acids, concentration not stated
      temperature: not stated
    source: espi-la-sds
    where: Section 10, Possibility of Hazardous Reactions and Incompatible Materials
risks:
  hazards:
    - text: 'PubChem GHS summary: 146 of 248 company reports (58.9 %) say the substance does not meet GHS criteria. Among the notified classifications, H228 flammable solid appears in 23.4 % and H260 (in contact with water releases flammable gases which may ignite spontaneously) in 19 %, with signal word Danger.'
      ghs:
        - H228
        - H260
      source: pubchem-la
      where: Safety and Hazards, Hazards Identification, GHS Classification
    - text: 'ESPI Metals SDS for lanthanum solid: GHS classification flammable solids, category 2, with hazard statement H228 and signal word Warning. Section 15 of the same SDS gives CLP as flammable solids, category 1, so the two sections disagree.'
      ghs:
        - H228
      source: espi-la-sds
      where: Section 2 Hazards Identification; Section 15 Regulatory Information
    - text: Kurt J. Lesker MSDS (1991) lists the metal as a DOT flammable solid. It says that lanthanum and lanthanons can cause delayed blood clotting leading to hemorrhages, and has caused liver injury in experimental animals. The same sheet says no toxicity data are available.
      ghs: []
      source: lesker-la-msds
      where: Section IV Fire and Explosion Hazard Data; Section VI Health Hazard Data
    - text: PubChem's hazards summary gives low to moderate acute toxicity, and lists lanthanum as fibrogenic (causing tissue injury and fibrosis).
      ghs: []
      source: pubchem-la
      where: Safety and Hazards, Hazards Summary; Toxicity, Adverse Effects
    - text: 'ESPI SDS transport entry: UN3178, flammable solid, inorganic, n.o.s. (Lanthanum), class 4.1, packing group II.'
      ghs: []
      source: espi-la-sds
      where: Section 14 Transport Information
    - text: Exposure limits differ by sheet. The Lesker MSDS lists a TLV of 10 mg/m3 and an OSHA PEL of 15 mg/m3. The ESPI and Ames SDSs both state that no OSHA PEL or ACGIH TLV has been established.
      ghs: []
      source: lesker-la-msds
      where: Section II Hazardous Ingredients, TLV and OSHA PEL columns; ESPI SDS Section 8 Exposure Limits
  failure_risks:
    - mode: Fire in chips, pieces, powder and dust
      trigger: Lanthanum pieces, powder or dust exposed to heat, sparks or flame, or dust raised during grinding or melting
      consequence: The metal is a flammable solid (H228) and will burn under fire conditions. The Lesker MSDS lists a dust explosion hazard, and the Ames SDS says grinding, melting or welding can produce hazardous dust or fumes.
      severity: high
      source: espi-la-sds
      where: Section 5 Firefighting Measures; Section 10 Possibility of Hazardous Reactions; Lesker MSDS Section IV Unusual Fire and Explosion Hazards
    - mode: Hydrogen release on contact with water or acid
      trigger: Metal in contact with water (especially under fire conditions) or with strong acids
      consequence: The reaction releases flammable hydrogen. PubChem's notifications record H260 (may ignite spontaneously) in 19 % of reports, and the ESPI SDS says the metal reacts vigorously with acids.
      severity: high
      source: pubchem-la
      where: Safety and Hazards, GHS Classification (H260 19 %); ESPI SDS Section 10
    - mode: Tarnishing and loss of surface in air
      trigger: Exposure to air, and especially moist air
      consequence: The surface darkens within hours. The Ames and ESPI sheets say the metal must be kept under argon, or under mineral oil in the Ames case, to avoid this.
      severity: moderate
      source: wikipedia-la
      where: Characteristics, Chemical, air reactivity; Ames SDS Section 7 Conditions for Safe Storage
    - mode: Reaction with halogens and strong oxidizers
      trigger: Contact with halogens, strong oxidizers, sulfur or phosphorus
      consequence: The Lesker MSDS lists these as materials to avoid. The sheet does not give a reaction rate or temperature, so the severity is an assessment from the listing alone.
      severity: moderate
      source: lesker-la-msds
      where: Section VII Reactivity Data, Incompatibility
  side_effects:
    - text: PubChem reports that a printer and a movie projectionist exposed to rare-earth metals in the dust of carbon arc lamps retained lanthanum in their lungs.
      affects: Workers exposed to lanthanum dust or fume
      source: pubchem-la
      where: Safety and Hazards, Hazards Summary
  handling:
    - text: Handle under dry argon in an enclosed, controlled process, and use local exhaust to keep dust below exposure limits (ESPI SDS). Do not blow dust off clothing or skin with compressed air.
      source: espi-la-sds
      where: Section 7 Handling and Storage; Section 8 Engineering Controls
    - text: Store in tightly sealed containers under argon, protect from water and moisture, and keep away from acids and oxidizers. The Ames SDS also allows mineral oil.
      source: ames-la-sds
      where: Section 7 Conditions for Safe Storage
    - text: 'Fire: use a Class D dry powder extinguisher and do not use water (ESPI SDS). The Lesker MSDS gives dry chemical and says do not use water, and firefighters should wear self-contained breathing apparatus.'
      source: lesker-la-msds
      where: Section IV Extinguishing Media and Special Fire Fighting Procedures
    - text: 'Spill: avoid raising dust, use non-sparking tools, sweep or scoop the material into a closed container, and do not use water for cleanup (ESPI SDS).'
      source: espi-la-sds
      where: Section 6 Accidental Release Measures
  mitigations: []
uses:
  - application: optics-and-cameras
    device: Lanthanum oxide in high-index optical glass for camera and telescope lenses (ground-manufactured)
    example: Wikipedia says lanthanum(III) oxide is used in optical glass, including camera and telescope lenses, because of its high refractive index. PubChem lists the same use for special optical glasses such as infrared-absorbing glass.
    source: wikipedia-la
    where: Applications section, lanthanum(III) oxide paragraph; PubChem Use and Manufacturing, Uses
  - application: propulsion-and-tanks
    device: Lanthanum hexaboride (LaB6) thermionic emitter in a hollow cathode for Hall thrusters (a compound, not the metal; design record, no flight reported)
    example: A NASA Tech Briefs record (2010) describes a compact hollow cathode with a LaB6 thermionic emitter that gives 10 to 60 A of emission and whose keeper diameter lets it sit on the centerline of a 6-kW Hall thruster. It says LaB6 needs less stringent xenon purity than barium oxide cathodes.
    source: ntrs-hollow-cathode-2010
    where: Abstract excerpts, "Compact Rare Earth Emitter Hollow Cathode", NASA Tech Briefs, March 2010
  - application: batteries
    device: Lanthanum-containing alloy anode in nickel-metal hydride (NiMH) rechargeable batteries (an alloy, not the metal)
    example: PubChem lists lanthanum as used in nickel-metal-hydride rechargeable batteries. Wikipedia says a lanthanum-containing alloy is one material used for the anode of nickel-metal hydride batteries.
    source: wikipedia-la
    where: Applications section, battery paragraph; PubChem Use and Manufacturing, Uses
supply:
  - subject: Rare earths (lanthanum is not reported separately by USGS)
    abundance: 39 mg/kg of the Earth's crust (Wikipedia, which cites a crust figure)
    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.'
    substitutes:
      - 'USGS: substitutes are available for many applications but generally are less effective.'
    source: usgs-ree-2026
    where: 'World Mine Production table, 2025 (world total 390,000 t, rounded; shares calculated by Space Mushroom from China 270,000, United States 51,000, Australia 29,000 and Burma 22,000). Recycling and Substitutes sections. Abundance: Wikipedia Occurrence section.'
  - subject: Lanthanum oxide price and China export controls
    producers: []
    critical_lists: []
    recycling: ''
    substitutes: []
    source: usgs-ree-2026
    where: 'Salient Statistics, price row Lanthanum oxide, 99.5% minimum, 1.00 dollars per kg in 2025e (0.97 in 2024). Events, Trends, and Issues: the April 2025 Chinese export controls name samarium, gadolinium, terbium, dysprosium, lutetium, scandium and yttrium, and do not name lanthanum.'
  - 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 to 2024) paragraph: China 71 %, Malaysia 13 %, Japan 5 %, Estonia 5 %. The year column shows the end of the 2021 to 2024 range. This covers all rare-earth compounds and metals, not lanthanum alone.'
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: Lanthanum'
    type: database
    url: https://en.wikipedia.org/wiki/Lanthanum
    year: 2026
  - title: PubChem compound record for lanthanum (CID 23926), including ECHA C&L Inventory classification
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/23926
    year: 2026
  - title: 'WebElements: Lanthanum, physical properties (University of Sheffield)'
    type: datasheet
    url: https://winter.group.shef.ac.uk/webelements/lanthanum/physics.html
  - title: 'Safety data sheet: Lanthanum solid (ESPI Metals), copy on the supplier site'
    type: sds
    url: https://www.espimetals.com/index.php/msds/500-lanthanum-msds
  - title: 'Kurt J. Lesker Company material safety data sheet: Lanthanum metal (revised 6/25/91)'
    type: sds
    url: https://www.lesker.com/newweb/deposition_materials/pdf/msds_la.pdf
    year: 1991
  - title: 'Safety data sheet: Lanthanum, Ames Laboratory 57 Lanthanum SDS (revised January 26, 2016)'
    type: sds
    url: https://www.external.ameslab.gov/sites/default/files/inline-files/57_Lanthanum_SDS.pdf
    year: 2016
  - title: Compact Rare Earth Emitter Hollow Cathode (NASA Tech Briefs, March 2010; NTRS 20100009696)
    type: paper
    url: https://ntrs.nasa.gov/citations/20100009696
    year: 2010
gaps:
  - 'Lanthanum-specific production: USGS reports rare earths as one group, so the producer shares above are for all rare earths, not for lanthanum. No year-stamped world output for lanthanum metal alone was found in an opened source.'
  - 'Critical-mineral listing: the USGS 2025 critical minerals list and the EU critical raw materials list were not opened for lanthanum, so critical_lists is empty.'
  - 'Space flight of lanthanum metal: no flight use of the metal was found. The only space-related source is the 2010 NASA Tech Briefs record for a LaB6 compound cathode, which reports a design and no flight.'
  - 'Mechanical strength: no tensile, yield or annealed strength for lanthanum metal was found in an opened source. The Goodfellow lanthanum product page returned HTTP 404 and was not read.'
  - 'Hardness: brinell_hardness and vickers_hardness are new names, because the property file has no canonical name for hardness. WebElements prints Brinell and Vickers in MN m-2, and Wikipedia gives a Brinell range.'
  - Melting point and density differ between sources (918 to 921 °C; 6.145 to 6.17 g/cc at 20 to 25 °C). All values are entered with their own source and conditions, and none has been averaged.
  - 'Boiling point: the Lesker sheet prints 3457 °C with a label that is not clear, so it is not entered. Wikipedia and PubChem both give 3464 °C.'
  - 'Hazard classification: the ESPI and Ames SDSs give flammable solid category 2 in Section 2 but category 1 in Section 15, and the 1991 Lesker sheet has no GHS statements. The PubChem notifications differ from the SDSs, and 58.9 % of its reports do not meet GHS criteria.'
  - 'Exposure limits: the Lesker sheet gives a TLV of 10 mg/m3 and an OSHA PEL of 15 mg/m3, while the ESPI and Ames sheets say no limit is established. Both are reported and neither is used as a limit.'
  - Corrosion data are qualitative (Wikipedia, PubChem and the SDS sheets). No measured weight-gain or corrosion-rate figure for lanthanum in air or water was found.
  - 'Superconducting transition temperature: the Wikipedia page as read did not include a value in its infobox text, so none is entered.'
  - The PubChem web page returned a browser check, so the record was read through PubChem's public REST view (pug_view) for CID 23926.
  - The American Elements, Stanford Advanced Materials and Sigma-Aldrich lanthanum SDSs were found in search results but not opened, and the Angstrom Sciences SDS was downloaded but not read in full.
  - 'Battery use: no open-access review of lanthanum in NiMH alloys was found. The battery use is supported only by the Wikipedia and PubChem statements, and it describes an alloy, not the metal.'
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-la:
    title: Lanthanum (Wikipedia)
    url: https://en.wikipedia.org/wiki/Lanthanum
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  pubchem-la:
    title: 'PubChem compound record: Lanthanum (CID 23926), including ECHA C&L Inventory classification'
    id: CAS 7439-91-0
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23926/JSON
    year: 2026
    kind: database
    license: PubChem (NCBI), public domain; sections attributed to ECHA and others
  webelements-la:
    title: 'WebElements: Lanthanum, physical properties (University of Sheffield)'
    url: https://winter.group.shef.ac.uk/webelements/lanthanum/physics.html
    kind: database
    license: WebElements, cited not reproduced
  espi-la-sds:
    title: 'Safety data sheet: Lanthanum solid (ESPI Metals)'
    id: CAS 7439-91-0; EC 231-099-0
    url: https://www.espimetals.com/index.php/msds/500-lanthanum-msds
    kind: datasheet
    license: supplier safety data sheet, cited not reproduced
  lesker-la-msds:
    title: 'Kurt J. Lesker Company material safety data sheet: Lanthanum metal (6/25/91)'
    id: CAS 7439-91-0
    url: https://www.lesker.com/newweb/deposition_materials/pdf/msds_la.pdf
    year: 1991
    kind: datasheet
    license: supplier safety data sheet, cited not reproduced
  ames-la-sds:
    title: 'Safety data sheet: Lanthanum, Ames Laboratory 57 Lanthanum SDS (revised January 26, 2016)'
    url: https://www.external.ameslab.gov/sites/default/files/inline-files/57_Lanthanum_SDS.pdf
    year: 2016
    kind: datasheet
    license: laboratory safety data sheet, cited not reproduced
  ntrs-hollow-cathode-2010:
    title: Compact Rare Earth Emitter Hollow Cathode (Watkins, Goebel, Hofer; NASA Tech Briefs, March 2010)
    id: NTRS 20100009696
    url: https://ntrs.nasa.gov/citations/20100009696
    year: 2010
    kind: paper
    license: NASA public record, cited not reproduced
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 26
  unreachable: 2
  caveats: 6
  note: 'Read by an AI assistant on 2026-10-26 from the pages and PDFs named in each entry. Unreachable: Goodfellow lanthanum metal page (HTTP 404); PubChem web page (browser check, read through the REST view instead). Caveats: most physical values come from Wikipedia and one WebElements page; supply shares are for all rare earths, not lanthanum; the boiling point and exposure limits differ between sources; the hazard classes differ between sections and dates; the LaB6 cathode is a compound design record.'
story:
  risk_groups:
    - title: For people
      lead: Lanthanum metal is classed as a flammable solid. Toxicity data are thin, and the sources disagree on exposure limits.
      level: 1
      verdict: Form-dependent
      points:
        - label: Chips, powder and dust
          line: The ESPI and Ames SDSs classify the metal as a flammable solid (H228), and the Lesker sheet lists a dust explosion hazard.
        - label: Water and acids
          line: Contact with water or strong acids releases hydrogen. PubChem records H260 (may ignite spontaneously) in 19 % of its notifications.
        - label: Dust limits
          line: The Lesker sheet gives a TLV of 10 mg/m3 and an OSHA PEL of 15 mg/m3. The ESPI and Ames sheets say no limit is established.
        - label: Toxicity
          line: PubChem gives low to moderate acute toxicity and calls lanthanum fibrogenic. The Lesker sheet mentions delayed blood clotting and liver injury in animals, and says no toxicity data are available.
    - title: If it fails
      lead: 'The sources give three failure routes: a fire in fine metal or dust, hydrogen release with water or acid, and tarnishing in moist air.'
      points:
        - label: Fire
          line: Use a Class D dry powder agent and do not use water on the burning metal (ESPI, Lesker).
        - label: Hydrogen
          line: Water or strong acid releases flammable hydrogen (ESPI, PubChem).
        - label: Tarnish
          line: The surface turns dark in air within hours, so it is kept under argon (Wikipedia, ESPI).
    - title: Handling and storage
      points:
        - label: Keep it dry
          line: Store in sealed containers under argon, protect from moisture, and keep away from acids and oxidizers (ESPI, Ames).
        - label: Dust control
          line: Handle in an enclosed process with local exhaust, and do not blow dust off clothing or skin with compressed air (ESPI).
  why: 'Lanthanum is a silvery rare-earth metal with a density of 6.145 g/cm3 at 20 °C and a melting point of 920 °C (Wikipedia). It is used mainly as lanthanum oxide in high-index optical glass, as an alloy component in nickel-metal-hydride battery anodes, and in catalysts. Its space-related interest is narrower: a NASA design record from 2010 describes lanthanum hexaboride, a compound, as the emitter in a Hall-thruster hollow cathode. No flight of the metal was found.'
  uses:
    - where: Optical glass
      line: Wikipedia says lanthanum(III) oxide is used in optical glass, including camera and telescope lenses, because of its high refractive index. PubChem lists the same optical uses.
    - where: Hall-thruster cathode emitter (design record)
      line: A NASA Tech Briefs record from March 2010 describes a compact hollow cathode with a LaB6 thermionic emitter that gives 10 to 60 A of emission and fits on the centerline of a 6-kW Hall thruster. It is a design record, and no flight is reported in it.
    - where: Nickel-metal-hydride batteries
      line: A lanthanum-containing alloy is one anode material in nickel-metal-hydride batteries (Wikipedia), and PubChem lists the same battery use.
  can_do:
    - label: Weight
      value: 6.145 g/cm3
      benchmark: density
      line: Density is 6.145 g/cm3 at 20 °C (Wikipedia). PubChem gives 6.166 at 25 °C, and the ESPI SDS gives 6.17 at 20 °C.
    - label: Melting
      value: 920 °C
      benchmark: melting_point
      line: Melting point is 920 °C (Wikipedia and PubChem). The ESPI SDS gives 918 °C, and the Lesker sheet gives 921 °C.
    - label: Heat conduction
      value: 13.4 W/(m·K)
      benchmark: thermal_conductivity
      line: Thermal conductivity is 13.4 W/(m·K) in the Wikipedia infobox, and WebElements gives 13 W/(m·K).
    - label: Stiffness
      value: 36.6 GPa
      benchmark: elastic_modulus
      line: Young's modulus of the alpha form is 36.6 GPa (Wikipedia). WebElements gives 37 GPa.
  compare: 'Lanthanum is a dense, soft rare-earth metal, at 6.145 g/cm3 with a melting point of 920 °C. Its thermal conductivity of 13.4 W/(m·K) is modest for a metal, and its Young''s modulus of about 37 GPa is low for a structural metal. Its value to designers is chemical: it is a flammable solid that tarnishes in air and releases hydrogen with water and acids, so it is used as an oxide in glass, not as a structural part. No comparison profile is carried in this file, so the rows below list lanthanum values only.'
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  recipe:
    line: Lanthanum is a single-element metal (La). Wikipedia says it is obtained by heating its oxide with ammonium chloride or fluoride, followed by reduction with an alkali or alkaline-earth metal in vacuum or argon. It can also be made by electrolysis of a molten mixture of anhydrous chlorides. It is mined with the other rare earths.
    parts:
      - name: Lanthanum
        symbol: La
        atoms: 1
        atomic_weight: 138.9055
        role: The whole material. The Lesker and ESPI sheets list 100 % lanthanum, and PubChem gives a molecular weight of 138.9055 for the element.
  handling:
    - Handle under dry argon in an enclosed process with local exhaust (ESPI).
    - Store in sealed containers under argon, away from moisture, acids and oxidizers (ESPI, Ames).
    - Do not use water on a fire. Use a Class D dry powder extinguisher (ESPI, Lesker).
    - Sweep spills into a closed container with non-sparking tools, and do not use water for cleanup (ESPI).
  good_for:
    - 'Optical glass: lanthanum oxide raises the refractive index, which is why it is used in camera and telescope lenses (Wikipedia).'
    - 'Electric-propulsion cathodes: the LaB6 emitter design gives 10 to 60 A in a compact hollow cathode (NASA Tech Briefs, 2010). This is a compound.'
    - 'Battery alloys: lanthanum-containing alloys are used as anodes in nickel-metal-hydride batteries (Wikipedia).'
  watch_out:
    - Flammable solid with a dust explosion hazard (ESPI, Lesker, Ames).
    - Water and strong acids release hydrogen, and the metal tarnishes in air within hours (ESPI, Wikipedia).
    - 'Supply is concentrated: China produced about 69 % of world rare-earth mine output in 2025, a group figure (USGS). Lanthanum oxide was not named in China''s April 2025 export controls (USGS).'
    - The SDSs disagree on GHS category and exposure limits, and most toxicology data are missing.
  verdict: Lanthanum is a dense rare-earth metal, at 6.145 g/cm3 with a melting point of 920 °C, whose practical value is as an oxide in optical glass and as a battery-alloy component. The metal itself is a flammable solid that tarnishes in air and reacts with water and acids, so it needs dry, argon-sealed handling. Its space link is a LaB6 compound cathode design from 2010, not a flown part of the metal.