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β-Tridymite
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Formula:
SiO2
Member of:
Polymorph of:
Beta-Tridymite (β-tridymite or high-tridymite) is a low pressure, high-temperature-stable polymorph of silica that occurs most notably as vapour-deposited, platey crystals in vesicles in some volcanic rocks, also rarely as phenocrysts in some felsic volcanics, or as a contact metamorphic material in some hornfels.
Below 100°C the triclinic form, α-tridymite is stable; there are also orthorhombic, monoclinic and hexagonal polytypes. The orthorhombic β-tridymite polytype is most stable at elevated temperatures (>870°C) and it converts to β-cristobalite above 1470°C. However, tridymite does not usually form directly from pure β-quartz, and it is usually stabilised by alkali metals. Otherwise β-quartz transitions directly to cristobalite at 1050°C without occurrence of the tridymite phase.
Below 100°C the triclinic form, α-tridymite is stable; there are also orthorhombic, monoclinic and hexagonal polytypes. The orthorhombic β-tridymite polytype is most stable at elevated temperatures (>870°C) and it converts to β-cristobalite above 1470°C. However, tridymite does not usually form directly from pure β-quartz, and it is usually stabilised by alkali metals. Otherwise β-quartz transitions directly to cristobalite at 1050°C without occurrence of the tridymite phase.
Name Encoding
CP1252:
b-Tridymite
Latin-1:
b-Tridymite
ASCII-7:
b-Tridymite
Unique Identifiers
Mindat ID:
47886
Long-form identifier:
mindat:1:1:47886:3
Similar Names
| Tridymite | A valid IMA mineral species - grandfathered | SiO2 |
| Tritomite | ||
| Tritomite-(Ce) | A valid IMA mineral species | Ce5(SiO4,BO4)3(OH,O) |
| Tritomite-(Y) | A valid IMA mineral species | Y5(SiO4,BO4)3(O,OH,F) |
Chemistry of β-Tridymite
Mindat Formula:
SiO2
Elements listed:
Synonyms of β-Tridymite
Relationship of β-Tridymite to other Species
Member of:
Other Members of Silica:
| Chibaite | SiO2 · n(CH4, C2H6, C3H8, i-C4H10) (n = 3/17 (max)) | Iso. m3(2/m3) : Fd3 |
| Coesite | SiO2 | Mon. 2/m : B2/b |
| Cristobalite | SiO2 | Tet. 422 : P41212 |
| 'Keatite' | SiO2 | Tet. 422 : P43212 |
| Lechatelierite | SiO2 | Amor. |
| Melanophlogite | 46SiO2 · 6(N2,CO2) · 2(CH4,N2) | Tet. 4/mmm(4/m2/m2/m) |
| Mogánite | SiO2 | Mon. 2/m |
| 'Opal-AG' | SiO2 · nH2O | |
| 'Opal-AN' | SiO2 · nH2O | |
| 'Opal-C' | SiO2 · nH2O | |
| 'Opal-CT' | SiO2 · nH2O | |
| Quartz | SiO2 | Trig. 32 : P3121 |
| 'Quartz-beta' | SiO2 | Hex. 622 : P6422 |
| Seifertite | SiO2 | Orth. mmm(2/m2/m2/m) : Pbcn |
| Stishovite | SiO2 | Tet. 4/mmm(4/m2/m2/m) : P42/mnm |
| Tridymite | SiO2 | Tric. 1 |
| 'β-Cristobalite' | SiO2 | Iso. m3m(4/m32/m) : Fd3m |
Other Information
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for β-Tridymite
mindat.org URL:
https://www.mindat.org/min-47886.html
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References for β-Tridymite
Reference List:
Cellai, D., Carpenter, M. A., Wruck, B., Salje, E.k.h. (1994) Characterization of high-temperature phase transitions in single crystals of Steinbach tridymite. American Mineralogist, 79 (7-8) 606-614
Localities for β-Tridymite
Showing 1 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
China | |
| Zhang et al. (2021) |
