Osmium Os

spore: profile
id: osmium
spore_version: 0.2
family: precious-metals
name: Osmium
abbreviation: Os
role: dense platinum-group metal for hard alloys, wear-resistant contacts and a space-flown optical coating
category: metals
type: precious-metals
summary: |
  Osmium is the metal Os, atomic number 76, a hard, brittle, blue-grey member of the platinum group. Goodfellow gives a density of 22.5 g/cm3 at 20 °C and a melting point of 3045 °C, and PubChem gives 3033 °C; the two sources differ by 12 °C. Its thermal conductivity is 87.6 W/(m·K) at 0 to 100 °C in one datasheet, and its bulk modulus is 410 GPa at zero temperature in a measured elastic study. Osmium is inert as a bulk metal but oxidises to volatile, highly toxic osmium tetroxide when heated in air or as a fine powder. An osmium-coated grating flew on the Spacelab 1 mission, and osmium coatings flown on early Shuttle test flights were lost to atomic oxygen.
best_for: Hard, dense alloys and wear-resistant electrical contacts where hardness and durability matter (Goodfellow, Tanaka)
weakest_at: Oxidation when heated in air or as a fine powder, which forms osmium tetroxide, a volatile and highly toxic compound (PubChem, Dartmouth); coatings were lost to atomic oxygen in orbit (NASA NTRS)
identity:
  formula: Os (element, atomic number 76); hexagonal close-packed metal
  cas: 7440-04-2
  crystal_system: hexagonal close-packed
  source: pubchem-os
  where: Names and Identifiers, Other Identifiers, CAS (CID 23937); crystal structure from Goodfellow, Atomic Properties table
tags:
  environments:
    - low-earth-orbit
  applications:
    - optics-and-cameras
    - electronics-and-chips
properties:
  - benchmark: density
    label: Density of osmium powder at 20 °C (Goodfellow)
    value: 22.5
    unit: g/cm3
    scope: material
    conditions:
      temperature: 20 °C
      form: 99.9% powder, as listed on the product page
    method: Value printed in the physical properties table of a manufacturer's datasheet
    status: ground
    source: goodfellow-os
    where: Physical Properties table, Density row
  - benchmark: density
    label: Density of solid osmium (WebElements)
    value: 22610
    unit: kg/m3
    scope: material
    conditions:
      state: solid
      temperature: not stated in the source
    method: Value printed in the density properties of a reference database
    status: ground
    source: webelements-os
    where: Density properties, Density of solid row
  - benchmark: melting_point
    label: Melting point (PubChem experimental)
    value: 3033
    unit: °C
    scope: material
    conditions:
      basis: experimental value listed in PubChem
    method: Value printed in the experimental properties of the PubChem compound record
    status: ground
    note: Goodfellow prints 3045 °C for the same metal; the two sources disagree.
    source: pubchem-os
    where: Chemical and Physical Properties, Experimental Properties, Melting Point
  - benchmark: melting_point
    label: Melting point (Goodfellow)
    value: 3045
    unit: °C
    scope: material
    conditions:
      form: powder datasheet value
    method: Value printed in the thermal properties table of a manufacturer's datasheet
    status: ground
    note: PubChem prints 3033 °C; the two sources disagree.
    source: goodfellow-os
    where: Thermal Properties table, Melting point row
  - benchmark: boiling_point
    label: Boiling point (PubChem experimental)
    value: 5012
    unit: °C
    scope: material
    conditions:
      pressure: 760 mm Hg, as printed by PubChem
    method: Value printed in the experimental properties of the PubChem compound record
    status: ground
    note: Goodfellow prints 5027 °C; the two sources disagree.
    source: pubchem-os
    where: Chemical and Physical Properties, Experimental Properties, Boiling Point
  - benchmark: boiling_point
    label: Boiling point (Goodfellow)
    value: 5027
    unit: °C
    scope: material
    conditions:
      form: powder datasheet value
    method: Value printed in the physical properties table of a manufacturer's datasheet
    status: ground
    note: PubChem prints 5012 °C; the two sources disagree.
    source: goodfellow-os
    where: Physical Properties table, Boiling point row
  - benchmark: specific_heat
    label: Specific heat of osmium (Goodfellow)
    value: 131
    unit: J/(kg·K)
    scope: material
    conditions:
      temperature: 25 (printed as @25, no unit given)
    method: Value printed in the thermal properties table of a manufacturer's datasheet, unit printed as J K-1 kg-1
    status: ground
    source: goodfellow-os
    where: Thermal Properties table, Specific heat row
  - benchmark: thermal_conductivity
    label: Thermal conductivity, 0 to 100 °C (Goodfellow)
    value: 87.6
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: 0 to 100 (printed as 0-100@, no unit given)
    method: Value printed in the thermal properties table of a manufacturer's datasheet, unit printed as W m-1 K-1
    status: ground
    source: goodfellow-os
    where: Thermal Properties table, Thermal conductivity row
  - benchmark: thermal_conductivity
    label: Thermal conductivity (WebElements)
    value: 88
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: not stated in the source
    method: Value printed in the thermal properties of a reference database, unit printed as W m-1 K-1
    status: ground
    source: webelements-os
    where: Thermal properties, Thermal conductivity row
  - benchmark: cte
    label: Coefficient of thermal expansion, 0 to 100 (Goodfellow)
    value: 4.57
    unit: ppm/K
    scope: material
    conditions:
      temperature: 0 to 100 (printed as 0-100, no unit given)
    method: Value printed as x10-6 K-1 in a manufacturer's thermal properties table; 4.57 x10-6 K-1 is 4.57 ppm/K
    status: ground
    source: goodfellow-os
    where: Thermal Properties table, Coefficient of thermal expansion row
  - benchmark: cte
    label: Coefficient of linear thermal expansion (WebElements)
    value: 5.1
    unit: ppm/K
    scope: material
    conditions:
      temperature: not stated in the source
    method: Printed as 5.1 x 10-6 K-1 in a reference database; 5.1 x 10-6 K-1 is 5.1 ppm/K. The two CTE values differ and both are kept.
    status: ground
    source: webelements-os
    where: Thermal properties, Coefficient of linear thermal expansion row
  - benchmark: elastic_modulus
    label: Tensile (Young's) modulus (Goodfellow)
    value: 559
    unit: GPa
    scope: material
    conditions:
      material_condition: as listed in the mechanical properties table, soft and hard rows show the same value
    method: Value printed in the mechanical properties table of a manufacturer's datasheet
    status: ground
    source: goodfellow-os
    where: Mechanical Properties table, Tensile modulus row
  - benchmark: shear_modulus
    label: Rigidity (shear) modulus (WebElements)
    value: 222
    unit: GPa
    scope: material
    conditions:
      temperature: not stated in the source
    method: Value printed in the elastic properties of a reference database
    status: ground
    source: webelements-os
    where: Density and elastic properties, Rigidity modulus row
  - benchmark: bulk_modulus
    label: Bulk modulus at zero temperature (measured, Pantea et al. 2009)
    value: 410
    unit: GPa
    scope: material
    conditions:
      temperature: 0 K (zero-temperature value extrapolated from the elastic constants)
      form: monocrystal and polycrystal measured by ultrasound and resonance ultrasound
    method: Value stated in the abstract of a measured elastic-constant study
    status: ground
    note: Contested in the literature. Earlier work reported a value above that of diamond. The 2009 study finds it does not exceed diamond at any temperature.
    source: pantea2009
    where: Abstract
  - benchmark: bulk_modulus
    label: Bulk modulus at 300 K (measured, Pantea et al. 2009)
    value: 405
    unit: GPa
    scope: material
    conditions:
      temperature: 300 K
    method: Value stated in the abstract of a measured elastic-constant study
    status: ground
    source: pantea2009
    where: Abstract
  - benchmark: poissons_ratio
    label: Poisson's ratio (WebElements)
    value: 0.25
    unit: '-'
    scope: material
    conditions:
      temperature: not stated in the source
    method: Printed without a unit in a reference database
    status: ground
    source: webelements-os
    where: Density and elastic properties, Poisson's ratio row
  - benchmark: vickers_hardness
    label: Vickers hardness, soft material condition (Goodfellow)
    value: 300
    value_high: 350
    bound: range
    unit: kgf/mm2
    scope: material
    conditions:
      material_condition: soft
    method: Range printed in the mechanical properties table of a manufacturer's datasheet
    status: ground
    source: goodfellow-os
    where: Mechanical Properties table, Hardness Vickers row, soft column
  - benchmark: vickers_hardness
    label: Vickers hardness, hard material condition (Goodfellow)
    value: 670
    value_high: 1000
    bound: range
    unit: kgf/mm2
    scope: material
    conditions:
      material_condition: hard
    method: Range printed in the mechanical properties table of a manufacturer's datasheet
    status: ground
    source: goodfellow-os
    where: Mechanical Properties table, Hardness Vickers row, hard column
  - benchmark: mohs_hardness
    label: Mineral (Mohs) hardness
    value: 7
    unit: '-'
    scope: material
    conditions:
      basis: Mohs scale, printed without a unit
    method: Value printed in the hardness section of a reference database
    status: ground
    source: webelements-os
    where: Hardnesses, Mineral hardness row
  - benchmark: brinell_hardness
    label: Brinell hardness (WebElements)
    value: 3920
    unit: MN/m2
    scope: material
    conditions:
      temperature: not stated in the source
    method: Value printed in the hardness section of a reference database
    status: ground
    source: webelements-os
    where: Hardnesses, Brinell hardness row
  - benchmark: debye_temperature
    label: Debye temperature from zero-temperature elastic constants
    value: 477
    unit: K
    scope: material
    conditions:
      basis: from zero-temperature elastic constants
    method: Value stated in the abstract of a measured elastic-constant study (not in the property canon)
    status: ground
    source: pantea2009
    where: Abstract
  - benchmark: gruneisen_parameter
    label: Gruneisen parameter from Gruneisen's first rule
    value: 2.1
    unit: '-'
    scope: material
    conditions:
      basis: from Gruneisen's first rule, using the measured elastic constants
    method: Value stated in the abstract of a measured elastic-constant study (not in the property canon)
    status: ground
    source: pantea2009
    where: Abstract
  - benchmark: electrical_resistivity
    label: Electrical resistivity at 20 °C (Goodfellow)
    value: 8.8
    unit: µΩ·cm
    scope: material
    conditions:
      temperature: 20 °C
    method: Value printed in the electrical properties table of a manufacturer's datasheet, unit printed as µOhmcm
    status: ground
    source: goodfellow-os
    where: Electrical Properties table, Electrical resistivity row
corrosion:
  - environment: Atomic oxygen in low Earth orbit (osmium samples on early Shuttle test flights)
    headline: Osmium coatings flown on early Shuttle test flights disappeared, which the authors attribute to oxidation in the atomic oxygen environment.
    effect: On the return of the samples the osmium coating was found to have disappeared. The authors attribute this to oxidation of the material in the atomic oxygen atmosphere in orbit. The abstract gives no flight duration or coating thickness.
    rating: severe
    conditions:
      exposure: early Shuttle test flights; flight duration not stated in the abstract
      coating: osmium coating on samples flown in orbit
    source: torr1985
    where: Abstract, first sentence
  - environment: Heated in air or as a finely divided powder
    headline: Osmium metal is inert at room temperature but oxidises to osmium tetroxide when heated in air or as a fine powder.
    effect: PubChem summarises that metallic osmium is inert, but when heated in air or in a finely divided form it oxidises to osmium tetroxide. The Dartmouth guideline says osmium tetroxide sublimes readily at room temperature.
    rating: moderate
    conditions:
      temperature: heated, temperature not given in the summary
      form: bulk metal heated in air, or fine powder
    source: pubchem-os
    where: Stability and Reactivity, Hazardous Reactivities and Incompatibilities
  - environment: Mineral acids and aqua regia
    headline: Osmium is insoluble in acids and aqua regia, and the manufacturer describes its corrosion resistance against acids and oxidising agents as remarkable.
    effect: PubChem lists the metal as insoluble in acids and aqua regia. Goodfellow describes remarkable corrosion resistance, particularly against acids and oxidising agents. Tanaka describes osmium alloy pen points as having high acid resistance.
    rating: low
    conditions:
      basis: solubility statement and manufacturer descriptions; no concentration or temperature given
    source: pubchem-os
    where: Chemical and Physical Properties, Experimental Properties, Solubility
  - environment: Fused alkalis
    headline: Molten alkali attacks osmium.
    effect: PubChem lists the metal as attacked by fused alkalis. The source does not give the alkali, temperature or time.
    rating: moderate
    conditions:
      basis: statement in PubChem; no temperature or alkali given
    source: pubchem-os
    where: Chemical and Physical Properties, Experimental Properties, Solubility
  - environment: Fluorine at elevated temperature
    headline: Osmium ignites when heated with fluorine.
    effect: PubChem reports that osmium ignites when heated to 100 °C with fluorine, and that it reacts incandescently with phosphorus vapour.
    rating: severe
    conditions:
      temperature: 100 °C
      reagent: fluorine
    source: pubchem-os
    where: Stability and Reactivity, Hazardous Reactivities and Incompatibilities
risks:
  hazards:
    - text: 'PubChem aggregates the notified classifications for elemental osmium: flammable solid (H228, 97.4% of reports), skin irritation (H315, 96.7%), serious eye damage (H318, 96.1%), respiratory irritation (H335, 96.7%) and long-lasting harmful effects to aquatic life (H413, 69.1%). The signal word is Danger.'
      ghs:
        - H228
        - H315
        - H318
        - H335
        - H413
      source: pubchem-os
      where: Safety and Hazards, GHS Classification (CID 23937)
    - text: A supplier safety data sheet for osmium powder classifies it as a flammable solid under H228 and gives the precautionary statements P210 (keep away from heat, sparks and open flames) and P241 (use explosion-proof equipment). It is a single supplier document, so check the sheet for the lot you handle.
      ghs:
        - H228
      source: chemicalbook-os-sds
      where: Sections 2 (Hazard statements and GHS label elements)
    - text: Osmium tetroxide, the oxide formed when osmium is heated in air, is a volatile, highly toxic solid. The guideline gives an oral rat LD50 of 14 mg/kg and says it sublimes readily at room temperature. This is a different compound from the metal, but the metal can produce it.
      ghs: []
      source: dartmouth-osu
      where: Page 1, hazard summary and Highly toxic section
  failure_risks:
    - mode: Dust fire
      trigger: Finely divided osmium exposed to heat or flame
      consequence: Flammable in the form of dust when exposed to heat or flame, according to PubChem. Fire response uses water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
      severity: moderate
      source: pubchem-os
      where: Safety and Hazards, Fire Potential
    - mode: Volatile oxide release in hot air
      trigger: Metal or fine powder heated in air
      consequence: Oxidation to osmium tetroxide, which sublimes at room temperature and is highly toxic. The PubChem summary says workers must be protected from the osmium tetroxide vapour produced when metallic osmium is handled hot.
      severity: high
      source: dartmouth-osu
      where: Page 1, Highly toxic and sublimation sections
    - mode: Coating loss in orbit
      trigger: Osmium surface exposed to the atomic oxygen environment of orbit
      consequence: Osmium coatings flown on early Shuttle test flights were found to have disappeared, which the authors attribute to oxidation in the atomic oxygen atmosphere.
      severity: high
      source: torr1985
      where: Abstract
  side_effects:
    - text: Aggregated GHS notifications list skin irritation, serious eye damage and respiratory irritation for the metal. Dust or hot vapour can reach the eyes and airways of people working with it.
      affects: Eyes, skin and airways of people handling the powder or hot metal
      source: pubchem-os
      where: Safety and Hazards, GHS Classification (hazard statements H315, H318 and H335)
    - text: The guideline describes osmium tetroxide vapour as causing severe eye and respiratory irritation, with possible chemical burns and organ damage.
      affects: Eyes and airways of people exposed to vapour from heated osmium
      source: dartmouth-osu
      where: Page 1, Highly toxic section
  handling:
    - text: 'PubChem: avoid dust formation and provide local exhaust ventilation where dust or fumes form. Metallic osmium should be handled with adequate ventilation to keep osmium tetroxide vapour out of the work area.'
      source: pubchem-os
      where: Accidental Release Measures, Preventive Measures
    - text: Keep away from heat, sparks and open flames, and use explosion-proof equipment (P210 and P241). Avoid dust formation. Sweep up spills with a vacuum that is electrically protected, or wet-brush them.
      source: chemicalbook-os-sds
      where: Sections 2 and 7 (precautionary statements and handling)
    - text: Do not let osmium meet fluorine or chlorine trifluoride. PubChem records ignition with fluorine at 100 °C and violent reactions with chlorine trifluoride.
      source: pubchem-os
      where: Stability and Reactivity, Hazardous Reactivities and Incompatibilities
  mitigations:
    - text: 'PubChem: workers dealing with metallic osmium should be protected from osmium tetroxide vapour by adequate ventilation.'
      source: pubchem-os
      where: Safety and Hazards, Accidental Release Measures, Preventive Measures
uses:
  - application: optics-and-cameras
    device: Osmium-coated reflective grating in an extreme-ultraviolet spectrometer on Spacelab 1 (flown)
    example: On the ten-day Spacelab 1 mission the osmium-coated reflective grating stayed stable, relative to a spectrometer with an MgF2 coating. The calibration ratio did not change in any major way over the two years from laboratory calibration to flight.
    source: torr1985
    where: Abstract
  - application: electronics-and-chips
    device: Wear-resistant electrical contacts and high-reliability switch contact points
    example: Goodfellow lists osmium powder for hardening platinum alloys, creating wear-resistant electrical contacts and contact points in high-reliability switches.
    source: goodfellow-os
    where: Product description, Applications paragraph
supply:
  - subject: Osmium in the Earth's crust
    abundance: 0.0015 ppm in the continental crust (USGS PP 1802-A Table A1, crustal abundances, citing Jefferson Science Associates, 2014)
    producers: []
    critical_lists:
      - list: EU critical raw materials list, entry 'Platinum group metals' (group entry; osmium is not named on its own)
        listed: true
    recycling: No osmium-specific recycling figure found. USGS gives about 140,000 kg of palladium and platinum recovered from scrap globally in 2025 (see the next entry).
    substitutes: []
    source: usgs-pp1802a
    where: Table A1, Os row; EU list on the European Commission critical raw materials page (ec-crm)
  - subject: Platinum-group metals (platinum mine production used as the group proxy; USGS does not break out osmium)
    producers:
      - country: South Africa
        share_percent: 70.6
        year: 2025
      - country: Russia
        share_percent: 11.8
        year: 2025
      - country: Zimbabwe
        share_percent: 10.6
        year: 2025
      - country: Canada
        share_percent: 2.9
        year: 2025
    critical_lists:
      - list: EU critical raw materials list, entry 'Platinum group metals'
        listed: true
    recycling: 'USGS: about 140,000 kg of palladium and platinum were recovered globally from new and old scrap in 2025, including about 8,600 kg of platinum from automobile catalytic converters in the United States.'
    substitutes:
      - 'USGS: for some industrial end uses one platinum-group metal can substitute for another, with losses in efficiency. No osmium-specific substitute is named.'
    source: usgs-mcs2026-pgm
    where: World Mine Production and Reserves table, Platinum 2025e column (world total 170,000 kg; shares calculated by Space Mushroom); Recycling; Substitutes
  - subject: Osmium imports to the United States
    abundance: 57 kg imported in 2025e and 1 kg in 2024 (USGS salient statistics)
    producers: []
    critical_lists: []
    recycling: See the platinum-group entry above.
    substitutes: []
    source: usgs-mcs2026-pgm
    where: Salient Statistics, Imports for consumption, Osmium row
media: []
documents:
  - title: 'PubChem: Osmium (CID 23937), GHS classification and experimental properties'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23937/JSON
    year: 2026
  - title: 'Goodfellow: Osmium Powder, product datasheet with material properties'
    type: datasheet
    url: https://www.goodfellow.com/m-f/osmium-powder
    year: 2026
  - title: 'WebElements: Osmium physical properties'
    type: database
    url: https://webelements.co.uk/osmium/physics.html
    year: 2026
  - title: Elastic constants of osmium between 5 and 300 K (Phys. Rev. B 80, 024112)
    type: paper
    url: https://impact.ornl.gov/en/publications/elastic-constants-of-osmium-between-5-and-300-k/
    year: 2009
  - title: Osmium coated diffraction grating in the Space Shuttle environment (Applied Optics 24)
    type: paper
    url: https://ntrs.nasa.gov/citations/19850066910
    year: 1985
  - title: 'NIST: Atomic Weights and Isotopic Compositions for Osmium'
    type: database
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Os&ascii=html
    year: 2026
  - title: Dartmouth College guidelines for safe use of osmium tetroxide
    type: report
    url: https://ehs.dartmouth.edu/sites/ehs/files/2024-05/dartmouth-college-guidelines-for-safe-use-of-osmium-tetroxide.pdf
    year: 2024
  - title: 'USGS Mineral Commodity Summaries 2026: Platinum-Group Metals'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-platinum-group.pdf
    year: 2026
  - title: 'USGS Professional Paper 1802-A: Critical Mineral Resources of the United States, Table A1'
    type: report
    url: https://pubs.usgs.gov/pp/1802/a/pp1802a.pdf
    year: 2017
gaps:
  - No flight or qualification test of an osmium structural part or contact was found. The only space results are an optical coating on one Spacelab 1 instrument, which the abstract describes as stable over a ten-day mission, and early Shuttle samples that lost their coating.
  - No osmium-specific mine production or country shares were found. The USGS platinum-group chapter gives platinum and palladium only, so the supply entry uses platinum mine production as a proxy and says so.
  - The USGS 2025 List of Critical Minerals page could not be opened (blocked), so the US critical-mineral status of osmium is not recorded. Only the EU group entry for platinum-group metals was read.
  - Density, melting point and boiling point disagree between sources (22.5 g/cm3 from Goodfellow against 22610 kg/m3 from WebElements; 3045 against 3033 °C melting; 5027 against 5012 °C boiling). Both values are kept, each with its source.
  - 'Bulk modulus: Goodfellow prints 373 GPa, which is not entered because it conflicts with the measured 405 to 410 GPa from Pantea et al. (2009). Earlier work reported a value above diamond; that claim was not entered.'
  - 'Electrical resistivity: WebElements prints it only in scientific notation, so it was not entered. The Goodfellow value of 8.8 µΩ·cm at 20 °C is the only one included.'
  - Hazard data rest on the PubChem aggregated notifications and one supplier SDS. American Elements and Thermo Fisher SDS pages could not be opened (blocked), so their hazard codes are not used.
  - 'No designation (UNS, EN or ASTM code) was added: osmium is sold as an element, powder or alloy component, not as a graded alloy, and no source printed a grade code for it.'
  - The properties debye_temperature, gruneisen_parameter, vickers_hardness, mohs_hardness and brinell_hardness are not in spores/property-canon.yaml, so snake_case names are used for them.
  - Wikipedia was used only for history and composition (discovery and isotopes). No Wikipedia value is used as a property.
  - No image was added to the media list.
sources:
  pubchem-os:
    title: PubChem compound record, Osmium (CID 23937)
    id: CID 23937; CAS 7440-04-2
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/23937/JSON
    year: 2026
    kind: database
    license: public domain (NCBI)
  goodfellow-os:
    title: Goodfellow, Osmium Powder, 99.9% (3N) product datasheet with material properties
    id: Goodfellow osmium powder, CAS 7440-04-2
    url: https://www.goodfellow.com/m-f/osmium-powder
    year: 2026
    kind: datasheet
    license: supplier datasheet, linked not reproduced
  webelements-os:
    title: 'WebElements, Osmium: physical properties'
    id: WebElements, element 76
    url: https://webelements.co.uk/osmium/physics.html
    year: 2026
    kind: database
    license: WebElements (reference, linked not reproduced)
  pantea2009:
    title: Elastic constants of osmium between 5 and 300 K
    id: doi:10.1103/PhysRevB.80.024112 (Phys. Rev. B 80, 024112)
    url: https://impact.ornl.gov/en/publications/elastic-constants-of-osmium-between-5-and-300-k/
    year: 2009
    kind: paper
    license: publisher record (ORNL repository abstract)
  torr1985:
    title: 'Osmium coated diffraction grating in the Space Shuttle environment: performance (Applied Optics 24)'
    id: NTRS 19850066910; doi not listed; Applied Optics 24, 1985
    url: https://ntrs.nasa.gov/citations/19850066910
    year: 1985
    kind: paper
    license: NASA NTRS record (public domain)
  nist-os:
    title: NIST, Atomic Weights and Isotopic Compositions for Osmium
    id: NIST physical reference data
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Os&ascii=html
    year: 2026
    kind: database
    license: public domain (NIST)
  chemicalbook-os-sds:
    title: ChemicalBook, Osmium safety data sheet (supplier SDS aggregator)
    id: CAS 7440-04-2
    url: https://www.chemicalbook.com/msds/osmium.htm
    year: 2026
    kind: datasheet
    license: supplier document, linked not reproduced
  dartmouth-osu:
    title: Dartmouth College guidelines for safe use of osmium tetroxide
    id: Dartmouth EHS, May 2024
    url: https://ehs.dartmouth.edu/sites/ehs/files/2024-05/dartmouth-college-guidelines-for-safe-use-of-osmium-tetroxide.pdf
    year: 2024
    kind: report
    license: institutional guideline, linked not reproduced
  usgs-mcs2026-pgm:
    title: Mineral Commodity Summaries 2026, Platinum-Group Metals
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-platinum-group.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-pp1802a:
    title: 'Critical Mineral Resources of the United States: An Introduction (Professional Paper 1802-A), Table A1'
    id: USGS PP 1802-A
    url: https://pubs.usgs.gov/pp/1802/a/pp1802a.pdf
    year: 2017
    kind: report
    license: public domain (USGS)
  ec-crm:
    title: Critical raw materials (European Commission, list under Regulation (EU) 2024/1252)
    id: Regulation (EU) 2024/1252
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    year: 2024
    kind: web
    license: European Commission web page
  wikipedia-os:
    title: Wikipedia, Osmium (history and composition only)
    id: Discovery section; isotopes section; lead paragraph (discovered in 1803 by Smithson Tennant)
    url: https://en.wikipedia.org/wiki/Osmium
    year: 2026
    kind: web
    license: CC BY-SA 4.0
  tanaka-os:
    title: 'Tanaka Precious Metals, Precious Metals Guide: Osmium'
    id: Tanaka element data, Os
    url: https://tanaka-preciousmetals.com/en/guide/element/os.html
    year: 2026
    kind: web
    license: manufacturer web page, linked not reproduced
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 23
  unreachable: 3
  caveats: 3
  note: 'Read by an AI assistant on 2026-10-26 from the pages named in each entry. Three pages could not be opened (American Elements SDS and product page, Thermo Fisher product page, USGS 2025 critical list page). Caveats: the density, melting point and boiling point sources disagree; the bulk modulus values differ between a datasheet and a measured study; the hazard codes come from PubChem aggregates and one supplier SDS.'
story:
  recipe:
    line: Osmium is a single element, Os, with atomic number 76. It is a hard, brittle, blue-grey metal of the platinum group that crystallises in the hexagonal close-packed structure. Wikipedia says it is separated from the other platinum-group metals by distillation or extraction of the volatile tetroxide.
    parts:
      - name: Osmium
        symbol: Os
        atoms: 1
        atomic_weight: 190.23
        role: The whole metal. Goodfellow describes it as the metal with the highest density of any naturally occurring element, and it is used to harden platinum alloys.
  risk_groups:
    - title: For people
      level: 0
      verdict: Flammable powder and toxic vapour when heated
      lead: The metal itself is a flammable solid when it is a fine powder. Heating it in air can produce osmium tetroxide, which is highly toxic.
      points:
        - label: The powder
          line: A supplier safety data sheet classifies osmium powder as a flammable solid (H228). PubChem's aggregated notifications list skin irritation, serious eye damage and respiratory irritation for the metal.
        - label: Heated metal
          line: Metallic osmium is inert, but when heated in air or as a fine powder it oxidises to osmium tetroxide. That oxide is volatile and sublimes readily at room temperature. The guideline gives an oral rat LD50 of 14 mg/kg.
        - label: Fire
          line: In a fire, use water spray, alcohol-resistant foam, dry chemical or carbon dioxide. Keep away from heat and sparks.
    - title: If a coating or part is heated or left in orbit
      lead: These results come from one laboratory description and one flight, not from routine use.
      points:
        - label: Orbit
          line: Osmium-coated samples flown on early Shuttle test flights were found to have disappeared, attributed to oxidation in the atomic oxygen of orbit.
        - label: Flight that worked
          line: An osmium-coated reflective grating in the extreme-ultraviolet spectrometer on the Spacelab 1 mission stayed stable over the ten-day flight, relative to an MgF2-coated spectrometer.
    - title: Handling and storage
      points:
        - label: Dust
          line: Avoid dust formation and use local exhaust ventilation where dust forms, as PubChem and the supplier sheet both advise.
        - label: Incompatible gases
          line: Keep osmium away from fluorine, which ignites it at 100 °C, and from chlorine trifluoride, which reacts violently.
  why: Osmium is a hard, dense platinum-group metal, and its value comes from hardness and durability. Goodfellow describes its powder as having the highest density of any naturally occurring element, and it is used to harden platinum alloys and to make wear-resistant electrical contacts. The metal is inert in bulk, but heating it in air produces osmium tetroxide, which is volatile and highly toxic, so handling and ventilation matter.
  uses:
    - where: Spacecraft optics
      line: An osmium-coated reflective grating flew in the extreme-ultraviolet spectrometer of the Spacelab 1 instrument array. Over a ten-day mission the coating stayed stable, relative to a spectrometer with an MgF2 coating. The abstract is the only space-flight source found for the metal.
    - where: Electrical contacts and switches
      line: Goodfellow lists osmium powder for hardening platinum alloys, creating wear-resistant electrical contacts and making contact points in high-reliability switches.
  can_do:
    - label: Density
      benchmark: density
      value: 22.5 g/cm3
      line: Goodfellow gives 22.5 g/cm3 at 20 °C, and WebElements gives 22610 kg/m3 for the solid. Goodfellow describes osmium as the highest-density naturally occurring element.
    - label: Melting point
      benchmark: melting_point
      value: 3045 °C
      line: The metal melts at 3045 °C in Goodfellow's datasheet and at 3033 °C in PubChem. The two sources differ by 12 °C.
    - label: Hardness
      benchmark: vickers_hardness
      value: 670 to 1000 kgf/mm2
      line: Goodfellow prints a Vickers hardness of 300 to 350 kgf/mm2 for the soft condition and 670 to 1000 kgf/mm2 for the hard condition.
    - label: Thermal conductivity
      benchmark: thermal_conductivity
      value: 87.6 W/(m·K)
      line: Goodfellow gives 87.6 W/(m·K) at 0 to 100 °C, close to the 88 W/(m·K) printed by WebElements.
  compare: Within this profile, the platinum-group comparison is limited. Goodfellow and PubChem give different melting and boiling points, and both are kept. The sources collected here do not compare osmium with other platinum-group metals, so no ranking is claimed.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  handling:
    - The powder is a flammable solid. Keep it away from heat, sparks and open flames.
    - Avoid dust. Use local exhaust ventilation where dust forms.
    - Heating the metal in air can produce osmium tetroxide, which is volatile and highly toxic. Ventilate the work area.
    - Keep it away from fluorine and chlorine trifluoride.
  good_for:
    - Hard, wear-resistant contacts. Goodfellow lists use in electrical contacts and high-reliability switches.
    - Acid resistance. PubChem lists the metal as insoluble in acids and aqua regia.
    - Thin reflective coatings in a space instrument. The Spacelab 1 grating stayed stable over a ten-day mission.
  watch_out:
    - Heated in air, it oxidises to volatile osmium tetroxide, which is highly toxic. PubChem and the Dartmouth guideline both describe this.
    - Coatings are vulnerable to atomic oxygen in orbit. Early Shuttle samples lost their osmium coating.
    - The sources disagree on density, melting point and boiling point. Check the datasheet used for a design.
  verdict: Osmium is a hard, dense platinum-group metal used for wear-resistant contacts and fountain-pen tips. It is inert as a bulk metal, but heat, fine powder and atomic oxygen each cause trouble, and the only space result found is one flight of an optical coating.