spore: profile
id: ruby
spore_version: 0.2
family: optical-crystals
name: Ruby (chromium-doped single-crystal alumina)
abbreviation: Cr:Al2O3
role: solid-state laser crystal, optical window and jewel bearing material
category: glasses-optics
type: optical-crystals
summary: |
  Ruby is alumina (Al2O3) grown as one crystal with a small amount of chromium (Cr3+) in place of aluminium. The laser-crystal supplier CRYLINK grows it by the Czochralski method and gives a density of 3.98 g/cm3, a Mohs hardness of 9 and a melting point of 2040 °C. Its datasheet lists a pump band of 450 to 532 nm and a tuning range of 680 to 1100 nm, which is what the chromium adds: it turns the crystal into a laser medium. In 1969 a ruby laser at Lick Observatory ranged to the Apollo 11 retroreflector, and NASA later used pulsed ruby light at a McDonald Observatory lunar-ranging station. Most values come from one supplier datasheet, so each value is kept with its own source.
best_for: Pulsed and tunable solid-state laser rods that need a hard, well-characterised crystal with a known pump band
weakest_at: 'Little space-qualification data: the sources read cover ground lasers, lunar ranging from Earth and one datasheet, with no ruby-specific radiation, outgassing or thermal-vacuum result'
identity:
  formula: Al2O3 with a Cr3+ dopant (Cr:Al2O3)
  crystal_system: trigonal (CRYLINK lists the crystal system as trigonal, with hexagonal axes a = 4.748 Å and c = 12.957 Å)
  source: crylink-ruby
  where: BASIC PARAMETERS table, Chemical Formula, Crystal System and Lattice Constant rows
tags:
  environments: []
  stresses: []
  applications:
    - optics-and-cameras
    - mechanisms
properties:
  - benchmark: density
    label: Density, CZ-grown Cr:Al2O3
    value: 3.98
    unit: g/cm3
    scope: material
    conditions:
      form: single crystal, Czochralski grown
      temperature: not stated
    method: Value printed in a supplier datasheet
    status: ground
    source: crylink-ruby
    where: BASIC PARAMETERS table, Density (g/cm3) row
  - benchmark: mohs_hardness
    label: Mohs hardness
    value: 9
    unit: '-'
    scope: material
    conditions:
      scale: Mohs
    method: Value printed in a supplier datasheet
    status: ground
    source: crylink-ruby
    where: BASIC PARAMETERS table, Mohs Hardness row
  - benchmark: melting_point
    label: Melting point
    value: 2040
    unit: °C
    scope: material
    conditions:
      form: single crystal, Czochralski grown
    method: Value printed in a supplier datasheet
    status: ground
    source: crylink-ruby
    where: BASIC PARAMETERS table, Melting Point row
  - benchmark: specific_heat
    label: Specific heat capacity at 18 °C
    value: 761
    unit: J/(kg·K)
    scope: material
    conditions:
      temperature: 18 °C
    method: Value printed in the datasheet as J kg-1 K-1; written in the same units
    status: ground
    source: crylink-ruby
    where: BASIC PARAMETERS table, Specific Heat Capacity @18°C row
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 25 °C, perpendicular to the c axis
    value: 0.35
    unit: W/(cm·K)
    scope: material
    conditions:
      temperature: 25 °C
      orientation: perpendicular to the c axis
    method: Value printed in the datasheet as W cm-1 K-1 and kept in that unit; 0.35 W/(cm·K) equals 35 W/(m·K)
    status: ground
    source: crylink-ruby
    where: BASIC PARAMETERS table, Thermal Conductivity @25°C, Perpendicular to the C axis row
  - benchmark: thermal_conductivity
    label: Thermal conductivity at 25 °C, parallel to the c axis
    value: 0.33
    unit: W/(cm·K)
    scope: material
    conditions:
      temperature: 25 °C
      orientation: parallel to the c axis
    method: Value printed in the datasheet as W cm-1 K-1 and kept in that unit; 0.33 W/(cm·K) equals 33 W/(m·K)
    status: ground
    source: crylink-ruby
    where: BASIC PARAMETERS table, Thermal Conductivity @25°C, Parallel to the C axis row
  - benchmark: cte
    label: Thermal expansion, perpendicular to the c axis, 20 to 100 °C
    value: 4.78
    unit: ppm/K
    scope: material
    conditions:
      temperature_range: 20 to 100 °C
      orientation: perpendicular to the c axis
    method: Printed as 4.78×10-6 K-1; 1 ppm/K equals 1×10-6 K-1
    status: ground
    source: crylink-ruby
    where: BASIC PARAMETERS table, Thermal Expansivity (20 – 100°C), Perpendicular to the C axis row
  - benchmark: cte
    label: Thermal expansion, parallel to the c axis, 20 to 100 °C
    value: 5.31
    unit: ppm/K
    scope: material
    conditions:
      temperature_range: 20 to 100 °C
      orientation: parallel to the c axis
    method: Printed as 5.31×10-6 K-1; 1 ppm/K equals 1×10-6 K-1
    status: ground
    source: crylink-ruby
    where: BASIC PARAMETERS table, Thermal Expansivity (20 – 100°C), Parallel to the C axis row
  - benchmark: refractive_index
    label: Refractive index, np
    value: 1.759
    unit: '-'
    scope: material
    conditions:
      wavelength: not stated on the datasheet
      label: np
    method: Value printed in a supplier datasheet
    status: ground
    source: crylink-ruby
    where: BASIC PARAMETERS table, Refractive Index row (np = 1.759)
  - benchmark: refractive_index
    label: Refractive index, nm
    value: 1.767
    unit: '-'
    scope: material
    conditions:
      wavelength: not stated on the datasheet
      label: nm
    method: Value printed in a supplier datasheet
    status: ground
    source: crylink-ruby
    where: BASIC PARAMETERS table, Refractive Index row (nm = 1.767)
  - benchmark: birefringence
    label: Birefringence
    value: 0.0082
    unit: '-'
    scope: material
    conditions:
      wavelength: not stated on the datasheet
    method: Value printed in a supplier datasheet, under the name Double Refraction
    status: ground
    source: crylink-ruby
    where: BASIC PARAMETERS table, Double Refraction row
  - benchmark: laser_tuning_range
    label: Laser tuning range
    value: 680
    value_high: 1100
    bound: range
    unit: nm
    scope: material
    conditions:
      use: solid-state laser output, Cr3+:Al2O3
    method: Range printed in a supplier datasheet
    status: ground
    source: crylink-ruby
    where: PARAMETERS table, Tuning Range (nm) row (680 – 1100)
  - benchmark: pump_wavelength_range
    label: Pump wavelength range
    value: 450
    value_high: 532
    bound: range
    unit: nm
    scope: material
    conditions:
      use: optical pumping of Cr3+:Al2O3
    method: Range printed in a supplier datasheet
    status: ground
    source: crylink-ruby
    where: PARAMETERS table, Pumping Range (nm) row (450 – 532)
  - benchmark: absorption_coefficient
    label: Absorption coefficient at 510 nm
    value: 0.5
    value_high: 2.5
    bound: range
    unit: cm-1
    scope: material
    conditions:
      wavelength: 510 nm
    method: Range printed in a supplier datasheet
    status: ground
    source: crylink-ruby
    where: PARAMETERS table, Absorption Coefficient @510 nm (cm-1) row (0.5 – 2.5)
corrosion: []
risks:
  hazards:
    - text: PubChem's record for chromium(III) oxide, Cr2O3, says it does not meet GHS hazard criteria for 57.8% (1112 of 1924) of reports. The minority classifications are H302 (24%), H317 (25.7%), H319 (24.3%) and H360 (14.6%), with signal word Danger. These describe the oxide powder, not a sealed or solid ruby crystal.
      ghs:
        - H302
        - H317
        - H319
        - H360
      source: pubchem-cr2o3
      where: Safety and Hazards, GHS Classification (CID 517277, chromia)
    - text: The CRYLINK datasheet has no safety or handling section. No safety data sheet for a ruby crystal was read in this run.
      ghs: []
      source: crylink-ruby
      where: Whole datasheet (no safety section)
  failure_risks:
    - mode: Misaligned crystal orientation
      trigger: A rod cut or mounted outside the datasheet orientation tolerance
      consequence: The datasheet sets the orientation at 90 degrees to the c axis with a tolerance below 5 degrees, so a rod outside that tolerance does not match the sold specification.
      severity: low
      source: crylink-ruby
      where: PARAMETERS table, Orientation and Orientation Tolerance rows
    - mode: Light outside the specified pump or tuning band
      trigger: Pump light outside 450 to 532 nm, or laser output outside 680 to 1100 nm
      consequence: The datasheet gives absorption of 0.5 to 2.5 per cm at 510 nm and specifies pump and tuning ranges only. Operation outside those bands is outside the supplier's specification.
      severity: moderate
      source: crylink-ruby
      where: PARAMETERS table, Pumping Range, Tuning Range and Absorption Coefficient rows
  side_effects: []
  handling:
    - text: The datasheet has no handling or storage section, and no fracture, handling or storage figure for ruby was read in this run.
      source: crylink-ruby
      where: Whole datasheet (no handling section)
  mitigations:
    - text: Specify the orientation and its tolerance when ordering. The datasheet gives an orientation tolerance below 5 degrees and an orientation of 90 degrees to the c axis.
      source: crylink-ruby
      where: PARAMETERS table, Orientation and Orientation Tolerance rows
uses:
  - application: optics-and-cameras
    device: Cr:Al2O3 laser rods for solid-state lasers
    example: CRYLINK sells ruby laser crystals from 3 to 40 mm in diameter and 10 to 140 mm long, for solid-state lasers, optical glass and watch parts.
    source: crylink-ruby
    where: DESCRIPTION and APPLICATIONS sections; PARAMETERS table, Dia and Length rows
  - application: optics-and-cameras
    device: Pulsed ruby laser ranging to the Apollo 11 retroreflector (Lick Observatory, 1969)
    example: On 1 August 1969 the Lick Observatory team fired a 1.2 GW ruby-crystal laser at the Apollo 11 retroreflector array and measured the round-trip time of the returning pulse.
    source: ieee-lure
    where: Milestone text, first paragraph; quote from Hal Walker, Jr.
  - application: optics-and-cameras
    device: Pulsed ruby laser lunar-ranging station at McDonald Observatory (2.7 m telescope)
    example: NASA's station description says the McDonald 2.7-m telescope transmits and receives pulsed ruby laser light for lunar ranging, in three 45-minute daily runs about three weeks a month.
    source: nasa1973
    where: Abstract (description of the lunar ranging station at McDonald Observatory)
  - application: mechanisms
    device: Jewel bearing rollers from drilled sapphire balls, and ruby balls in valves and probe tips
    example: Machine Design says sapphire balls can be drilled for use as precision jeweled bearing rollers for low-friction, long-wear use, and that ruby balls are used in chemical pump-check valves, wind indicators and probe tips.
    source: machinedesign
    where: Uses and Bearings section
supply:
  - subject: Alumina feedstock for ruby (world alumina production, 2025 estimate)
    producers:
      - country: China
        share_percent: 62
        year: 2025
      - country: Australia
        share_percent: 11.3
        year: 2025
      - country: Brazil
        share_percent: 7.3
        year: 2025
      - country: India
        share_percent: 5.5
        year: 2025
    critical_lists: []
    recycling: 'USGS: Recycling: None (bauxite and alumina chapter).'
    substitutes:
      - USGS names silicon carbide and alumina zirconia as substitutes in some abrasive and refractory uses. The chapter names no substitute for alumina used in single-crystal growth.
    source: usgs-mcs2026-bauxite
    where: World Alumina Refinery and Bauxite Mine Production table, alumina 2025e (world total 150,000 thousand t; China 93,000, Australia 17,000, Brazil 11,000, India 8,200). Shares calculated by Space Mushroom from these values. The chapter does not give ruby output.
  - subject: Chromium dopant (chromium mine production, 2025 estimate)
    producers:
      - country: South Africa
        share_percent: 45.1
        year: 2025
      - country: Turkey
        share_percent: 17.6
        year: 2025
      - country: Kazakhstan
        share_percent: 13.7
        year: 2025
      - country: India
        share_percent: 5.9
        year: 2025
    critical_lists: []
    recycling: 'USGS: In 2025, recycled chromium contained in reported stainless-steel scrap receipts accounted for 21% of apparent consumption.'
    substitutes:
      - 'USGS: chromium has no substitute in stainless steel or in superalloys. The chapter does not discuss its use as a laser dopant.'
    source: usgs-mcs2026-chromium
    where: World Mine Production and Reserves table, 2025e column (world total 51,000 thousand t, chromium content). Shares calculated by Space Mushroom from these values. Recycling and Substitutes paragraphs.
documents:
  - title: 'CRYLINK: Laser crystal Cr:Al2O3 (ruby) datasheet, two versions read (values agree)'
    type: datasheet
    url: https://www.laser-crylink.com/wp-content/uploads/CrAL2O3-Crylink.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Chromium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Bauxite and Alumina'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-bauxite-alumina.pdf
    year: 2026
  - title: 'PubChem: Chromia (chromium(III) oxide, CID 517277), GHS classification summary, pug_view record'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/517277/JSON
    year: 2026
  - title: 'NASA grant NsG-331: Exchange-coupled chromium ion pairs in ruby (L. F. Mollenauer, Stanford report 1329, May 1965)'
    type: report
    url: https://ntrs.nasa.gov/citations/19660030055
    year: 1965
  - title: 'NASA Technical Reports Server: A description of the lunar ranging station at McDonald Observatory'
    type: report
    url: https://ntrs.nasa.gov/citations/19730027447
    year: 1973
  - title: 'IEEE Milestone: Apollo 11 Lunar Ranging Experiment (LURE), 1969'
    type: report
    url: https://ieeemilestones.ethw.org/Milestones:Apollo_11_Lunar_Ranging_Experiment_(LURE)
    year: 2019
  - title: 'Machine Design: Synthetic sapphire and ruby for precision uses (trade article)'
    type: report
    url: https://www.machinedesign.com/archive/article/21821174/synthetic-sapphire-ruby-for-precision-uses
    year: 2026
gaps:
  - No ruby-specific flight, vacuum, outgassing, atomic-oxygen or radiation-ageing result was found in a source opened in this run. The space-related records are a 1965 spectroscopy report (NASA grant NsG-331), a NASA lunar-ranging station description and a 1969 ground ranging test.
  - 'No ruby mechanical data beyond Mohs hardness were read: no Vickers or Knoop hardness, flexural or tensile strength, fracture toughness, elastic modulus or Poisson ratio for ruby.'
  - Birefringence has no wavelength on the datasheet and no canonical property name; it is kept as birefringence.
  - Laser tuning range, pump wavelength range and absorption coefficient are not canonical property names; snake_case names are used for them.
  - The datasheet does not state the wavelength for the refractive index values or what the labels np and nm mean beyond the printed labels.
  - The chromium level in commercial laser rods was not read from a datasheet. Wikipedia gives around 0.05% of the crystal, used here for composition only. The 1965 NASA report quotes a Cr2O3 concentration for an early dark ruby rod, but the text copy prints the percent sign as a garbled character, so that figure is not used as a value.
  - Atomic weights of Al, O and Cr are not entered, because no source read in this run gives them.
  - No corrosion, etching, water or humidity data for ruby was found. The sapphire wet-etch paper concerns undoped sapphire and is not used here.
  - No ruby-specific safety data sheet was read. The PubChem record covers chromium(III) oxide notifications, not a ruby crystal, and no dust exposure limit for ruby was found.
  - No storage conditions or handling limits for ruby crystals were found.
  - No ruby crystal production output or grower country shares were found. Supply uses USGS alumina production and chromium mine production as feedstock figures, not ruby output. The critical-mineral status of chromium was not checked against the 2025 list.
  - 'No standard grade designations (UNS, EN, DIN, JIS) were applied: none of the sources read prints one for ruby.'
  - The space bearing use is not sourced. The 2021 MDPI paper on sapphire jewel bearings for space magnetic suspension returned HTTP 403 and was not read. The bearing use here is the Machine Design article, which covers sapphire balls and ruby balls, not flight hardware.
  - The 694.3 nm ruby laser line appears in Wikipedia, which is used here for composition only, so it is not entered as a property. No NASA or supplier value for the line was read in this run.
  - A Crystran ruby page was not found in search. The Northrop Grumman laser crystal page did not render text in this run.
  - The CRYLINK datasheet is undated; its year is the access year (2026). Two versions of the datasheet were read and their values agree.
  - The Machine Design text was read through a summarising fetch tool, so its quotes are extracts rather than a raw copy of the page.
  - The 1 August 1969 date and the 1.2 GW laser power come from one IEEE milestone page and are not checked against a second source.
  - 'No media entries were added: no ruby images were read in this run.'
sources:
  crylink-ruby:
    title: 'CRYLINK: Laser crystal Cr:Al2O3 (ruby), basic parameters and spectra datasheet'
    id: CrAL2O3-Crylink.pdf (undated)
    url: https://www.laser-crylink.com/wp-content/uploads/CrAL2O3-Crylink.pdf
    year: 2026
    kind: datasheet
    license: supplier document, linked not reproduced
  usgs-mcs2026-chromium:
    title: 'USGS Mineral Commodity Summaries 2026: Chromium'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-bauxite:
    title: 'USGS Mineral Commodity Summaries 2026: Bauxite and Alumina'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-bauxite-alumina.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  pubchem-cr2o3:
    title: PubChem compound record, Chromia (CID 517277), GHS classification
    id: CID 517277 (Cr2O3)
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/517277/JSON
    year: 2026
    kind: database
    license: public domain (NCBI)
  nasa1966:
    title: Exchange-coupled chromium ion pairs in ruby (L. F. Mollenauer, Stanford Microwave Laboratory report 1329, NASA grant NsG-331)
    id: NTRS 19660030055; May 1965
    url: https://ntrs.nasa.gov/citations/19660030055
    year: 1965
    kind: report
    license: public domain (NASA)
  nasa1973:
    title: A description of the lunar ranging station at McDonald Observatory (NASA Technical Reports Server)
    id: NTRS 19730027447
    url: https://ntrs.nasa.gov/citations/19730027447
    year: 1973
    kind: report
    license: public domain (NASA)
  ieee-lure:
    title: 'IEEE Milestone: Apollo 11 Lunar Ranging Experiment (LURE), 1969'
    id: ethw.org milestone page (oldid 7773)
    url: https://ieeemilestones.ethw.org/Milestones:Apollo_11_Lunar_Ranging_Experiment_(LURE)
    year: 2019
    kind: web
    license: IEEE milestone page, linked not reproduced
  machinedesign:
    title: 'Machine Design: Synthetic sapphire and ruby for precision uses'
    id: machinedesign.com article 21821174
    url: https://www.machinedesign.com/archive/article/21821174/synthetic-sapphire-ruby-for-precision-uses
    year: 2026
    kind: web
    license: trade article, linked not reproduced
  wiki-ruby:
    title: 'Wikipedia: Ruby laser (composition only)'
    id: en.wikipedia.org/wiki/Ruby_laser
    url: https://en.wikipedia.org/wiki/Ruby_laser
    year: 2026
    kind: web
    license: CC BY-SA 4.0
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 14
  unreachable: 1
  caveats: 5
  note: 'Written by an AI assistant on 2026-10-26 from pages and PDFs read in the same run. Caveats: all physical property values come from one supplier datasheet; the NASA 1965 report text is OCR-like and its dopant figure is not used; the Machine Design text came through a summarising fetch; the MDPI bearing paper returned HTTP 403; the dopant level is from Wikipedia.'
story:
  recipe:
    line: Ruby is alumina grown as one crystal, with chromium (Cr3+) taking a small share of the metal sites in place of aluminium. CRYLINK gives the formula as Cr3+:Al2O3 and the growth method as Czochralski (CZ). Wikipedia says the dopant is around 0.05% of the crystal and is responsible for all of the absorption and emission, and that synthetic ruby is pink or red depending on the dopant concentration.
    parts:
      - name: Aluminium oxide host lattice
        symbol: Al2O3
        share: the bulk of the crystal; atom counts and atomic weights not found in the sources opened
        role: The host crystal. The chromium sits in some of its metal sites.
      - name: Chromium
        symbol: Cr
        share: around 0.05% of the crystal (Wikipedia)
        role: Cr3+ activator ion. It causes the blue and green absorption bands and the laser emission.
  risk_groups:
    - title: For people
      level: 1
      verdict: No ruby-specific safety sheet was read
      lead: The only hazard records read are PubChem's entries for chromium(III) oxide powder, which are minority notifications. They do not describe a solid ruby crystal.
      points:
        - label: Minority classifications
          line: PubChem lists H302, H317, H319 and H360 for some chromium(III) oxide notifications, with signal word Danger. These concern powder, not a solid crystal.
        - label: Datasheet
          line: The CRYLINK datasheet has no safety section.
    - title: If it fails
      lead: The failure information comes from the supplier datasheet and from NASA-era records. No flight failure was read.
      points:
        - label: Orientation
          line: The datasheet sets the orientation tolerance below 5 degrees, so a rod cut outside it does not match the specification.
        - label: Wavelength band
          line: The datasheet gives a pump band of 450 to 532 nm and a tuning range of 680 to 1100 nm. Light outside these bands is outside the specification.
    - title: Handling and storage
      gap: No storage or handling limit for ruby was read in this run.
      points:
        - label: Protective equipment
          line: No ruby-specific guidance was read. The chromium(III) oxide record gives precautionary codes but not their text.
  why: 'Ruby is alumina with a chromium dopant. Its datasheet gives a density of 3.98 g/cm3, a Mohs hardness of 9 and a melting point of 2040 °C. The chromium is what makes it a laser: the datasheet lists pump and tuning ranges, and a ruby laser was used for lunar ranging from Earth in 1969.'
  uses:
    - where: Laser rods
      line: CRYLINK sells ruby laser crystals for solid-state lasers, in diameters of 3 to 40 mm and lengths of 10 to 140 mm.
    - where: Lunar ranging, 1969
      line: The Lick Observatory team used a 1.2 GW ruby-crystal laser to range to the Apollo 11 retroreflector on 1 August 1969. The IEEE milestone page calls it the first Earth-to-Moon distance measurement with centimetre accuracy.
    - where: McDonald lunar-ranging station
      line: NASA's station description says the McDonald 2.7-m telescope uses pulsed ruby laser light for lunar ranging.
    - where: Bearings and probes
      line: Machine Design says sapphire balls can be drilled for jeweled bearing rollers, and ruby balls are used in valves and probe tips. No flight bearing record for ruby was read.
  can_do:
    - label: Hardness
      value: Mohs 9
      line: CRYLINK gives a Mohs hardness of 9 for ruby. No Vickers or fracture figure was read.
    - label: Heat
      value: 2040 °C
      line: The melting point is 2040 °C and the specific heat is 761 J/(kg·K) at 18 °C, both from the CRYLINK datasheet.
    - label: Laser band
      value: 680 to 1100 nm
      line: The tuning range is 680 to 1100 nm, and the pump range is 450 to 532 nm. The absorption coefficient at 510 nm is 0.5 to 2.5 per cm.
    - label: Pulse energy in 1969
      value: 1.2 GW
      line: The Lick Observatory ruby-crystal laser was rated at 1.2 GW (IEEE milestone page). This is a ground instrument, not a space-rated one.
  compare: 'Compared with undoped sapphire in sapphire.yaml, ruby has nearly the same density and melting point. The difference is the chromium: about 0.05% of the crystal, which gives the pink or red colour, the absorption bands and the laser action. Ruby''s datasheet gives 35 W/(m·K) at 25 °C perpendicular to the c axis, while the Kyocera sheet cited in sapphire.yaml gives a higher figure at 20 °C. Those are different suppliers at different temperatures, so the gap is not a like-for-like test. Sapphire''s profile gives a transmission range and radiation results that this profile does not have for ruby.'
  compare_rows:
    - label: Density
      benchmark: density
    - label: Heat conduction
      benchmark: thermal_conductivity
    - label: Thermal expansion
      benchmark: cte
  handling:
    - No ruby-specific safety data sheet was read. Treat the crystal as a dust and sharp-edge hazard until a supplier sheet says otherwise.
    - Ask the supplier for the orientation and its tolerance, which the datasheet gives as below 5 degrees for ordinary rods.
    - The chromium(III) oxide powder record lists precautionary codes, but their text was not read; do not rely on it for a crystal.
  good_for:
    - Pulsed and tunable laser rods, with a pump band of 450 to 532 nm and a tuning range of 680 to 1100 nm (CRYLINK).
    - Hard, stiff optical and bearing parts where Mohs 9 is needed (CRYLINK for hardness, Machine Design for ball use).
    - Ground lunar ranging, as the 1969 Lick and McDonald work showed (IEEE milestone, NASA station description).
  watch_out:
    - Space data is thin. No ruby radiation, outgassing or thermal-vacuum result was found, and the NASA items are ground or lunar-ranging records.
    - Values come from one supplier. CRYLINK is the source for all physical properties, and the datasheet is undated.
    - Orientation matters. The datasheet asks for 90 degrees to the c axis with less than 5 degrees of tolerance.
    - Dopant level varies. The 0.05% figure is from Wikipedia, not from a rod datasheet, and early dark rods used a different chromium level.
  verdict: Ruby is sapphire with a chromium dopant, and the dopant is what makes it a laser. Its datasheet gives hardness, density, a pump band and a tuning range. The space record is ground lunar ranging in 1969 and ball use in valves and probes, not flight hardware, so a ruby-specific radiation and outgassing check is needed before any space use.