spore: profile
id: crystal-quartz
spore_version: 0.2
family: optical-crystals
name: Crystal quartz (alpha-quartz single crystal, SiO2)
abbreviation: SiO2
role: birefringent optical retarder, polariser and piezoelectric frequency-control crystal
category: glasses-optics
type: optical-crystals
summary: |
  Crystal quartz is alpha-quartz, crystalline silicon dioxide grown as a single crystal for optics and frequency control. Crystran gives a density of 2.649 g/cc and a melting point of 1710 °C, and says quartz should not be used above 490 °C because it starts to revert to a glassy state. Korth Kristalle gives a maximum application temperature above 1200 °C, so the two suppliers disagree on the usable limit.
best_for: Birefringent optics such as wave plates and polarisers, and piezoelectric frequency control in electronics.
weakest_at: 'Heat: Crystran says it starts to revert to a glassy state above 490 °C, far below its 1710 °C melting point.'
identity:
  formula: SiO2
  cas: 14808-60-7
  crystal_system: trigonal (hexagonal axes); Korth Kristalle gives a = 4.9138 Å and c = 5.4052 Å
  space_group: P3(2)21 (RH) and P3(1)21 (LH)
  source: crystran-quartz-page
  where: Product Data table, Class/Structure row (Trigonal (hex) P3(2)21 (RH) and P3(1)21 (LH)); formula from the page heading Crystal Quartz SiO2; CAS 14808-60-7 from crystran-quartz-sds section 3.1; lattice constants from korth-quartz, Crystal Structure row
tags:
  environments: []
  stresses:
    - total-radiation-dose
  applications:
    - optics-and-cameras
    - electronics-and-chips
properties:
  - benchmark: density
    label: Density, Crystran
    value: 2.649
    unit: g/cm3
    scope: material
    conditions:
      form: synthetic optical-grade crystal (alpha-quartz)
      temperature: not stated on the page
      unit_in_source: g/cc
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Density row
  - benchmark: density
    label: Density, Korth Kristalle
    value: 2.65
    unit: g/cm3
    scope: material
    conditions:
      form: synthetic single crystal (hydrothermal)
      temperature: not stated on the page
    method: Value printed on a manufacturer material page (English version)
    status: ground
    source: korth-quartz
    where: Properties table, Density row
  - benchmark: melting_point
    label: Melting point, Crystran
    value: 1710
    unit: °C
    scope: material
    conditions:
      form: synthetic crystal
    method: Value printed on a manufacturer product data page
    status: ground
    note: Korth Kristalle gives 1723 °C for the same material; the two values differ and both are kept.
    source: crystran-quartz-page
    where: Product Data table, Melting Point row
  - benchmark: melting_point
    label: Melting point, Korth Kristalle
    value: 1723
    unit: °C
    scope: material
    conditions:
      form: synthetic single crystal
    method: Value printed on a manufacturer material page (English version)
    status: ground
    note: Crystran gives 1710 °C for the same material; the two values differ and both are kept.
    source: korth-quartz
    where: Properties table, Melting point row
  - benchmark: boiling_point
    label: Boiling point at 760 mm Hg, as printed in the safety data sheet
    value: 2230
    unit: °C
    scope: material
    conditions:
      pressure: 760 mm Hg, as printed
    method: Value printed in a supplier safety data sheet
    status: ground
    note: Printed only in the safety data sheet; the Crystran data sheet and the Korth Kristalle page give no boiling point.
    source: crystran-quartz-sds
    where: Section 9.1, Boiling point (760mm Hg) row
  - benchmark: thermal_conductivity
    label: Thermal conductivity, para direction (as printed by Crystran)
    value: 10.7
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: 323 K
      orientation: para, as printed (the page does not define the direction)
      unit_in_source: W m-1 K-1
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Thermal Conductivity row
  - benchmark: thermal_conductivity
    label: Thermal conductivity, perp direction (as printed by Crystran)
    value: 6.2
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: 323 K
      orientation: perp, as printed (the page does not define the direction)
      unit_in_source: W m-1 K-1
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Thermal Conductivity row
  - benchmark: thermal_conductivity
    label: Thermal conductivity, parallel to the c axis (Korth Kristalle)
    value: 11.7
    unit: W/(m·K)
    scope: material
    conditions:
      temperature: 293 K
      orientation: parallel to the c axis, as printed as || C
    method: Value printed on a manufacturer material page (English version)
    status: ground
    source: korth-quartz
    where: Properties table, Thermal Conductivity row
  - benchmark: specific_heat
    label: Specific heat capacity, Crystran
    value: 710
    unit: J/(kg·K)
    scope: material
    conditions:
      temperature: not stated on the page
      unit_in_source: J Kg-1 K-1
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Specific Heat Capacity row
  - benchmark: specific_heat
    label: Specific heat capacity, Korth Kristalle
    value: 744
    unit: J/(kg·K)
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on a manufacturer material page (English version)
    status: ground
    note: Crystran gives 710 J/(kg·K); the two values differ and both are kept.
    source: korth-quartz
    where: Properties table, Spec. Heat Capacity row
  - benchmark: elastic_modulus
    label: Young's modulus, para direction (as printed by Crystran)
    value: 97.2
    unit: GPa
    scope: material
    conditions:
      orientation: para, as printed (the page does not define the direction)
      temperature: not stated on the page
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Youngs Modulus (E) row
  - benchmark: elastic_modulus
    label: Young's modulus, perp direction (as printed by Crystran)
    value: 76.5
    unit: GPa
    scope: material
    conditions:
      orientation: perp, as printed (the page does not define the direction)
      temperature: not stated on the page
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Youngs Modulus (E) row
  - benchmark: elastic_modulus
    label: Young's modulus, parallel to the c axis (Korth Kristalle)
    value: 97
    unit: GPa
    scope: material
    conditions:
      orientation: parallel to the c axis, as printed as || C
      temperature: 25 °C
    method: Value printed on a manufacturer material page (English version)
    status: ground
    note: Crystran gives 97.2 GPa in the para direction; the two values agree closely but are kept with their sources.
    source: korth-quartz
    where: Properties table, Young's Modulus row
  - benchmark: shear_modulus
    label: Shear modulus, Crystran
    value: 31.14
    unit: GPa
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Shear Modulus (G) row
  - benchmark: bulk_modulus
    label: Bulk modulus, Crystran
    value: 36.4
    unit: GPa
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on a manufacturer product data page
    status: ground
    note: Korth Kristalle gives 98 GPa for bulk modulus; the sources disagree and both are kept.
    source: crystran-quartz-page
    where: Product Data table, Bulk Modulus (K) row
  - benchmark: bulk_modulus
    label: Bulk modulus, Korth Kristalle
    value: 98
    unit: GPa
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on a manufacturer material page (English version)
    status: ground
    note: Crystran gives 36.4 GPa for bulk modulus; the sources disagree and both are kept.
    source: korth-quartz
    where: Properties table, Bulk Modulus row
  - benchmark: poissons_ratio
    label: Poisson's ratio, Korth Kristalle
    value: 0.08
    unit: '-'
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on a manufacturer material page (English version)
    status: ground
    note: Crystran prints n/a for Poisson ratio.
    source: korth-quartz
    where: Properties table, Poisson Ratio row
  - benchmark: dielectric_constant
    label: Dielectric constant, para direction (as printed by Crystran)
    value: 4.34
    unit: '-'
    scope: material
    conditions:
      frequency: 30 MHz
      orientation: para, as printed (the page does not define the direction)
    method: Value printed on a manufacturer product data page
    status: ground
    note: Korth Kristalle assigns 4.27 to the parallel direction and 4.34 to the perpendicular one, the reverse of this row.
    source: crystran-quartz-page
    where: Product Data table, Dielectric Constant row
  - benchmark: dielectric_constant
    label: Dielectric constant, perp direction (as printed by Crystran)
    value: 4.27
    unit: '-'
    scope: material
    conditions:
      frequency: 30 MHz
      orientation: perp, as printed (the page does not define the direction)
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Dielectric Constant row
  - benchmark: refractive_index
    label: Ordinary refractive index, no (Crystran)
    value: 1.54421
    unit: '-'
    scope: material
    conditions:
      wavelength: 0.6 µm
      ray: ordinary (no), as printed
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Refractive Index row
  - benchmark: refractive_index
    label: Extraordinary refractive index, ne (Crystran)
    value: 1.55333
    unit: '-'
    scope: material
    conditions:
      wavelength: 0.6 µm
      ray: extraordinary (Ne), as printed
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Refractive Index row
  - benchmark: refractive_index
    label: Ordinary refractive index, no (Korth Kristalle)
    value: 1.543
    unit: '-'
    scope: material
    conditions:
      wavelength: 633 nm
      ray: ordinary (no), as printed
    method: Value printed on a manufacturer material page (English version)
    status: ground
    source: korth-quartz
    where: Properties table, Refractive Index row
  - benchmark: refractive_index
    label: Extraordinary refractive index, ne (Korth Kristalle)
    value: 1.552
    unit: '-'
    scope: material
    conditions:
      wavelength: 633 nm
      ray: extraordinary (ne), as printed
    method: Value printed on a manufacturer material page (English version)
    status: ground
    source: korth-quartz
    where: Properties table, Refractive Index row
  - benchmark: transmission_range
    label: Transmission range, Crystran
    value: 0.18
    value_high: 3.5
    bound: range
    unit: µm
    scope: material
    conditions:
      thickness: not stated on the page
      note: a second band of 40 to 100 µm is printed separately
    method: Range printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Transmission Range row
  - benchmark: transmission_range
    label: Transmission range, Korth Kristalle
    value: 0.15
    value_high: 4.1
    bound: range
    unit: µm
    scope: material
    conditions:
      thickness: 2 mm
    method: Range printed on a manufacturer material page (English version)
    status: ground
    source: korth-quartz
    where: Properties table, Transmission Range row (thickness 2 mm)
  - benchmark: max_service_temp
    label: Upper temperature limit for use, Crystran
    value: 490
    unit: °C
    bound: upper
    scope: material
    conditions:
      basis: 'stated as: should not be processed or used at temperatures greater than 490 °C'
    method: Limit printed as a warning in the product description on a manufacturer page
    status: ground
    note: Korth Kristalle gives a maximum application temperature above 1200 °C; the two limits conflict and both are kept.
    source: crystran-quartz-page
    where: Product description paragraph (Quartz should not be processed or used at temperatures greater than 490 °C)
  - benchmark: max_service_temp
    label: Maximum application temperature, Korth Kristalle
    value: 1200
    unit: °C
    bound: lower
    scope: material
    conditions:
      basis: 'printed as: max. temperature for application > 1200°C'
    method: Value printed on a manufacturer material page (English version)
    status: ground
    note: Crystran gives an upper limit of 490 °C for use; the two limits conflict and both are kept.
    source: korth-quartz
    where: Remarks, Quartz is common, max. temperature for application > 1200°C
  - benchmark: knoop_hardness
    label: Knoop hardness, Crystran
    value: 741
    unit: HK
    scope: material
    conditions:
      load: 500 g indenter
      unit_in_source: printed as Knoop 741 with 500g indenter; no separate unit printed
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Hardness row
  - benchmark: elastic_limit
    label: Apparent elastic limit, Crystran
    value: 41
    unit: MPa
    scope: material
    conditions:
      test: not stated on the page
      unit_in_source: MPa (5950psi printed)
    method: Value printed on a manufacturer product data page
    status: ground
    source: crystran-quartz-page
    where: Product Data table, Apparent Elastic Limit row
corrosion:
  - environment: Hydrofluoric acid, fluosilicic acid, phosphoric acid and strong hot alkali solutions
    headline: Hydrofluoric acid and hot concentrated alkalis damage quartz, but no data sheet gives a rate.
    effect: Korth Kristalle states that quartz will be damaged by contact with HF and hot concentrated alkalines. Crystran's safety data sheet lists strong hot alkali solutions and hydrofluoric, fluosilicic and phosphoric acids as conditions to avoid. Neither source gives a rate or a time, so the rating is unknown.
    rating: unknown
    conditions:
      basis: statements in two supplier documents; no test or exposure time given
    source: korth-quartz
    where: Remarks; Crystran SDS is cited in the same entry's effect text (crystran-quartz-sds, section 10.4)
  - environment: Strong mineral acids
    headline: Crystran lists strong mineral acids as incompatible; Korth Kristalle says quartz is insoluble in acids.
    effect: Crystran's safety data sheet says quartz reacts with some mineral acids and lists strong mineral acids as incompatible. Korth Kristalle describes quartz as unsoluble in acids. The two statements differ, and no rate is given.
    rating: unknown
    conditions:
      basis: supplier safety data sheet statements; no test given
    source: crystran-quartz-sds
    where: Sections 10.1 and 10.5
  - environment: Water
    headline: Solubility in water is described differently by the two Crystran documents.
    effect: Crystran's data sheet lists solubility as Insoluble in water. Crystran's safety data sheet describes the product as practically soluble in water. The NTP profile of crystalline silica describes silica as practically insoluble in water at 20°C. No dissolution rate is given in any source.
    rating: unknown
    conditions:
      basis: statements in supplier and government documents; no test given
    source: crystran-quartz-sds
    where: Section 9.1, Solubility in water row
  - environment: Heating above the reversion limit (thermal ageing)
    headline: Above 490 °C quartz reverts to a glassy state, and Crystran says fracture is probable.
    effect: Crystran says crystal quartz starts to revert to a glassy state above 490 °C and that the process is complete by 530°C. It adds that, as annealing is unlikely, fracture of the component is probable. The rating is severe because the page states that fracture is probable.
    rating: severe
    conditions:
      temperature_range: above 490 °C, complete by 530°C
    source: crystran-quartz-page
    where: Product description paragraph
risks:
  hazards:
    - text: Crystran's safety data sheet says the product is 'No Hazardous Product as specified in Directive 67/548/EEC' and gives the precautionary statement P262, Do not breathe dust/fume/gas/mist/vapours/spray.
      ghs: []
      source: crystran-quartz-sds
      where: Sections 2.1 and 2.2
    - text: 'Crystran''s safety data sheet gives an occupational limit of ''Total inhalable silica dust: Long term 0.1 mg/m3''.'
      ghs: []
      source: crystran-quartz-sds
      where: Section 8.1, Control parameters
    - text: Respirable crystalline silica, primarily quartz dust, is 'Known to be a human carcinogen' in the NTP Report on Carcinogens.
      ghs: []
      source: ntp-silica
      where: Silica, Crystalline (Respirable Size) profile, Known to be a human carcinogen line
    - text: 'PubChem''s GHS summary for the generic Silica record (CID 24261), which is not specific to quartz, includes a block with ''H350 (12.6%): May cause cancer'', ''H372 (46%)'' and ''H373 (29.4%)'' from aggregated company reports.'
      ghs:
        - H350
        - H372
        - H373
      source: pubchem-silica
      where: Safety and Hazards, GHS Classification (Danger block)
  failure_risks:
    - mode: Reversion to a glassy state on heating
      trigger: Use or processing above 490 °C
      consequence: Crystran says crystal quartz starts to revert to a glassy state above 490 °C, the process is complete by 530°C, and fracture of the component is probable.
      severity: high
      source: crystran-quartz-page
      where: Product description paragraph
    - mode: Cracking at the alpha-to-beta transition
      trigger: Heating through the change to beta (high) quartz; the temperature is not given by Korth Kristalle
      consequence: Korth Kristalle says the change to beta quartz is reversible but can lead to breaks or cracks in the material.
      severity: moderate
      source: korth-quartz
      where: Remarks, standard modification text
    - mode: Frequency shift of quartz resonators in space radiation
      trigger: Exposure on NASA's Long Duration Exposure Facility (LDEF)
      consequence: Resonators of swept premium-Q quartz showed a frequency change attributed to recovery of radiation damage; resonators of natural quartz did not.
      severity: moderate
      source: nasa-ntrs-19920018076
      where: Abstract
  handling:
    - text: Protect the material against physical damage and avoid generating dust (Crystran SDS, section 7.2).
      source: crystran-quartz-sds
      where: Section 7.2
    - text: Safety goggles or safety glasses with side shields are required if there is any possibility of chipping or dust creation; wash hands after handling.
      source: crystran-quartz-sds
      where: Section 8.1, Exposure controls
    - text: Keep away from strong mineral acids and hydrofluoric acid; the SDS lists them as incompatible or conditions to avoid.
      source: crystran-quartz-sds
      where: Sections 10.4 and 10.5
  mitigations:
    - text: Keep use and processing below 490 °C, as Crystran advises.
      source: crystran-quartz-page
      where: Product description paragraph
uses:
  - application: optics-and-cameras
    device: Quarter-wave plates and polarisers (wave retardation)
    example: 'Crystran says crystalline quartz is used extensively as a wave retardation medium in quarter-wave plates and in polarisers. Korth Kristalle lists the same main applications: polariser, wave or retardation plate and VUV filter.'
    source: crystran-quartz-page
    where: Product description paragraph; Korth Kristalle Remarks
  - application: electronics-and-chips
    device: Frequency-control oscillators, frequency filters and timers
    example: The USGS 2026 chapter says electronic-grade quartz crystal is used to make frequency controls, frequency filters and timers in electronic circuits, and that electronic applications account for most industrial uses of quartz crystal.
    source: usgs-mcs2026-quartz
    where: Industrial cultured quartz crystal section, first paragraph
  - application: electronics-and-chips
    device: Quartz crystal resonators exposed on NASA's Long Duration Exposure Facility
    example: A 1992 LDEF symposium abstract reports that resonators of swept premium-Q quartz changed frequency after space exposure, while resonators of natural quartz did not.
    source: nasa-ntrs-19920018076
    where: Abstract
supply:
  - subject: Cultured piezoelectric quartz crystal, United States imports by origin (2021 to 2024)
    producers:
      - country: China
        share_percent: 89
        year: 2024
      - country: Denmark
        share_percent: 3
        year: 2024
      - country: Japan
        share_percent: 3
        year: 2024
    critical_lists: []
    recycling: 'USGS: an unspecified amount of rejected cultured quartz crystal was used as feed material for the production of cultured quartz crystal.'
    substitutes:
      - 'USGS: silicon is increasingly being used as a substitute for quartz crystal for frequency-control oscillators in electronic circuits.'
      - 'USGS: cultured quartz can be used as a substitute for ground high-purity quartz, although it is not commonly done owing to the high price of cultured quartz.'
    source: usgs-mcs2026-quartz
    where: Import Sources (2021-24) line; Recycling; Substitutes. The share of 'other' (5%) is not a country and is omitted.
media: []
documents:
  - title: Crystal Quartz (SiO2) safety data sheet, Crystran Ltd (revision 2016)
    type: sds
    url: https://www.crystran.com/wp-content/uploads/2025/09/quartz-crystal-sio2-msds.pdf
    year: 2016
  - title: Quartz Crystal (SiO2) data sheet, Crystran Ltd
    type: datasheet
    url: https://www.crystran.com/wp-content/uploads/2025/09/quartz-crystal-sio2-data-sheet.pdf
    year: 2025
  - title: SiO2 Quartz Crystal material page, Korth Kristalle GmbH
    type: datasheet
    url: https://www.korth.de/en/materials/detail/Quartz%20Crystal
  - title: 'Mineral Commodity Summaries 2026: Quartz (high-purity and industrial cultured crystal), USGS'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-quartz.pdf
    year: 2026
  - title: Study of factors determining the radiation sensitivity of quartz crystal oscillators (NASA NTRS 19920018076)
    type: report
    url: https://ntrs.nasa.gov/citations/19920018076
    year: 1992
  - title: 'PubChem: Silica (CID 24261), GHS classification summary'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/24261
  - title: 'NTP Report on Carcinogens, Fifteenth Edition: Silica, Crystalline (Respirable Size)'
    type: report
    url: https://ntp.niehs.nih.gov/ntp/roc/content/profiles/silica.pdf
gaps:
  - Thermal expansion coefficients (parallel and perpendicular directions) are printed with powers of ten on both the Crystran and Korth Kristalle pages, so they are left out.
  - The Korth Kristalle hardness row is labelled Mohs but gives a Knoop-scale figure; it is not recorded. The Mohs hardness value was not taken from a data sheet in this run.
  - The Korth Kristalle perpendicular thermal conductivity is printed without a unit, so it is left out.
  - The alpha-to-beta transition temperature is not taken from a data source in this run; Wikipedia is used here only for composition and history.
  - No space-environment numbers were found beyond the LDEF abstract, which gives no values; no flight data, orbit or dose figures were recorded.
  - Crustal abundance of quartz was not found in the USGS chapter, which gives no mine production shares for the world.
  - The USGS chapter does not state critical-mineral status for quartz crystal, so no critical-list entries are recorded.
  - 'Atomic weights for the recipe were not taken: the NIST table page fetched was the all-elements table, without a usable single-element row.'
  - 'Non-canonical property names used: knoop_hardness, elastic_limit and transmission_range. They are not in spores/property-canon.yaml.'
  - Dielectric, bulk modulus and maximum temperature values differ between Crystran and Korth Kristalle; both are kept with their sources and no value was chosen.
  - No ultraviolet or radiation transmission data were found for this grade; the LDEF abstract is qualitative only.
sources:
  crystran-quartz-page:
    title: Crystal Quartz SiO2, product data page, Crystran Ltd
    url: https://www.crystran.com/optical-materials/crystal-quartz-sio2/
    kind: datasheet
    license: supplier web page, cited not reproduced
  crystran-quartz-datasheet:
    title: Quartz Crystal (SiO2) data sheet, Crystran Ltd (PDF)
    url: https://www.crystran.com/wp-content/uploads/2025/09/quartz-crystal-sio2-data-sheet.pdf
    year: 2025
    kind: datasheet
    license: supplier document, cited not reproduced
  crystran-quartz-sds:
    title: 'Safety Data Sheet: Quartz (SiO2) Optical Crystal, Crystran Ltd'
    id: revision 2016, issued 12 October 2016
    url: https://www.crystran.com/wp-content/uploads/2025/09/quartz-crystal-sio2-msds.pdf
    year: 2016
    kind: datasheet
    license: supplier document, cited not reproduced
  korth-quartz:
    title: SiO2 Quartz Crystal, Korth Kristalle GmbH material page
    url: https://www.korth.de/en/materials/detail/Quartz%20Crystal
    kind: datasheet
    license: supplier web page, cited not reproduced
  usgs-mcs2026-quartz:
    title: 'Mineral Commodity Summaries 2026: Quartz (high-purity and industrial cultured crystal)'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-quartz.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  nasa-ntrs-19920018076:
    title: Study of factors determining the radiation sensitivity of quartz crystal oscillators (A0189), Second LDEF Post-Retrieval Symposium abstracts
    id: NTRS 19920018076
    url: https://ntrs.nasa.gov/citations/19920018076
    year: 1992
    kind: report
    license: public domain (NASA)
  pubchem-silica:
    title: PubChem compound record, Silica (CID 24261), GHS classification
    id: CID 24261
    url: https://pubchem.ncbi.nlm.nih.gov/compound/24261
    year: 2026
    kind: database
    license: public domain (NCBI)
  wikipedia-quartz:
    title: Quartz (Wikipedia article)
    url: https://en.wikipedia.org/wiki/Quartz
    kind: web
    license: CC BY-SA 4.0 (Wikipedia), cited for composition and history only
  ntp-silica:
    title: 'Report on Carcinogens, Fifteenth Edition: Silica, Crystalline (Respirable Size), National Toxicology Program'
    url: https://ntp.niehs.nih.gov/ntp/roc/content/profiles/silica.pdf
    kind: report
    license: public domain (NTP)
license: CC-BY-4.0
updated: '2026-11-02'
review:
  status: draft
  method: assistant
  checked_values: 29
  unreachable: 0
  caveats: 11
  note: Values read from pages fetched in this run. Crystran and Korth Kristalle disagree on several values (melting point, bulk modulus, dielectric direction, maximum temperature, specific heat); both are kept with their own sources.
story:
  recipe:
    line: Quartz is crystalline silicon dioxide, SiO2. Each silicon atom sits at the centre of a tetrahedron of four oxygen atoms, and the tetrahedra share corners to form a framework (Wikipedia). Optical quartz is grown synthetically by a hydrothermal process at high temperature and pressure (Korth Kristalle).
    parts:
      - name: Silicon
        symbol: Si
        role: Centre of each SiO4 tetrahedron, the building block of the framework that gives quartz its crystal structure.
        source: wikipedia-quartz
        where: Composition and crystal structure text
      - name: Oxygen
        symbol: O
        role: Shared between two tetrahedra in the framework; with one silicon it gives the SiO2 formula.
        source: wikipedia-quartz
        where: Composition and crystal structure text
  why: 'Crystal quartz is single-crystal silicon dioxide grown for optics and frequency control. Crystran says optical quartz is used extensively as a wave retardation medium; the crystal has two refractive indices (1.54421 and 1.55333 at 0.6 µm). It is piezoelectric, and electronic-grade quartz crystal is used for frequency controls. Its limit is heat: the crystal reverts to a glassy state above 490 °C.'
  uses:
    - where: Wave plates and polarisers
      line: Crystran says crystalline quartz is used extensively as a wave retardation medium in quarter-wave plates and in polarisers. Korth Kristalle names the same main optical applications.
    - where: Frequency control in electronics
      line: The USGS 2026 chapter says electronic-grade quartz crystal is used for frequency controls, frequency filters and timers, and that electronics accounts for most industrial uses of quartz crystal.
    - where: Tested as resonators in space
      line: A 1992 NASA abstract reports that quartz resonators of swept premium-Q material changed frequency after exposure on the Long Duration Exposure Facility, while resonators of natural quartz did not.
  can_do:
    - label: Optical transmission
      benchmark: transmission_range
      value: 0.18 to 3.5 µm (Crystran); 0.15 to 4.1 µm (Korth, 2 mm)
      line: It transmits from the ultraviolet into the near infrared. Crystran and Korth Kristalle print different ranges, and both are kept.
    - label: Birefringence
      benchmark: refractive_index
      value: 1.54421 and 1.55333 at 0.6 µm (Crystran)
      line: The two refractive indices differ, so light polarised along different axes travels at different speeds. This is the property that makes wave plates work.
    - label: Stiffness
      benchmark: elastic_modulus
      value: 97.2 GPa and 76.5 GPa (Crystran, para and perp)
      line: Young's modulus is 97.2 GPa in the para direction and 76.5 GPa in the perp direction, as Crystran prints them. The page does not define the directions.
    - label: Hardness
      benchmark: knoop_hardness
      value: Knoop 741 with a 500 g indenter (Crystran)
      line: Crystran gives a Knoop hardness of 741 with a 500 g indenter.
    - label: Heat limit
      benchmark: max_service_temp
      value: 490 °C (Crystran) and above 1200 °C (Korth)
      line: Crystran says quartz should not be used above 490 °C. Korth Kristalle gives a maximum application temperature above 1200 °C. The two limits conflict, and the lower one is the safer guide.
  compare: Crystran notes that fused quartz is the glassy, non-crystalline form better known as silica, so the two should not be confused. Crystal quartz is birefringent, and that property is why it is used for wave plates. Its melting point is 1710 °C (Crystran), but Crystran's use limit is 490 °C because above that temperature the crystal reverts to a glassy state. The table compares its density, melting point and thermal conductivity.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  handling:
    - Avoid generating dust. Crystran's safety data sheet says to protect the material from physical damage and avoid generating dust.
    - Wear safety glasses with side shields where chipping or dust is possible.
    - Keep it away from strong mineral acids and hydrofluoric acid, which the data sheets list as incompatible or damaging.
    - Keep use and processing below 490 °C, as Crystran advises.
  good_for:
    - Wave plates and polarisers. Crystran and Korth Kristalle both name these as the main optical uses.
    - Frequency control. The USGS names frequency controls, filters and timers as the main electronic use of cultured quartz.
    - Windows and optics from the ultraviolet to the near infrared, within the temperature limit above.
  watch_out:
    - Heat. Crystran says quartz reverts to a glassy state above 490 °C, far below its 1710 °C melting point.
    - Acids and hot alkalis. Korth Kristalle says hydrofluoric acid and hot concentrated alkalis damage it.
    - Conflicting data sheets. Density, specific heat, bulk modulus, dielectric direction and maximum temperature differ between Crystran and Korth Kristalle.
    - Cracking on phase change. Korth Kristalle says the alpha-to-beta change can lead to breaks or cracks.
    - Radiation. A NASA abstract reports frequency shifts in swept premium-Q resonators after LDEF exposure.
  verdict: Quartz is a well-documented birefringent optical and frequency-control crystal. Its data sheets disagree on several values and on the usable heat limit, so check the supplier's current datasheet before design use.
  risk_groups:
    - title: For people
      level: 2
      verdict: Dust is the hazard; avoid breathing it
      lead: The supplier says the product is not hazardous as a substance, but the dust is a recognised carcinogen risk.
      points:
        - label: The product
          line: 'Crystran''s safety data sheet says it is not a hazardous product under Directive 67/548/EEC and gives the precautionary statement P262: do not breathe dust.'
        - label: Respirable dust
          line: The NTP lists respirable crystalline silica, mainly quartz dust, as known to be a human carcinogen.
        - label: Limit
          line: Crystran's safety data sheet gives a long-term limit of 0.1 mg/m3 for total inhalable silica dust.
    - title: If it overheats
      level: 2
      verdict: Fracture risk above 490 °C
      lead: Heating changes the crystal structure, so the limit is set by the structure, not by the melting point.
      points:
        - label: Above 490 °C
          line: Crystran says the crystal starts to revert to a glassy state above 490 °C, the change is complete by 530°C, and fracture of the component is probable.
        - label: Cracking
          line: Korth Kristalle says the alpha-to-beta change is reversible but can lead to breaks or cracks.
    - title: Chemicals
      level: 1
      verdict: Keep away from strong acids and hot alkali
      lead: The data sheets name specific chemicals to avoid.
      points:
        - label: Acids and alkalis
          line: Korth Kristalle says hydrofluoric acid and hot concentrated alkalis damage quartz. Crystran lists strong hot alkali solutions and hydrofluoric, fluosilicic and phosphoric acids as conditions to avoid.