Tobermorite
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| Tobermorite | |
|---|---|
 Crystal structure of tobermorite: elementary unit cell viewed in 3D | |
| General | |
| Category |
Silicate mineral, Calcium silicate hydrate |
| Formula (repeating unit) |
Ca5Si6O16(OH)2·4H2O, or; Ca5Si6(O,OH)18·5H2O |
| Crystal symmetry | Orthorhombic 2 2 2 |
| Unit cell | a = 11.17 Å, b = 7.38 Å, c = 22.94 Å; β = 90°; Z = 4 |
| Identification | |
| Formula mass | 702.36 |
| Color | Pale pinkish white, white, brown |
| Crystal habit | As minute laths; fibrous bundles, rosettes or sheaves, radiating or plumose, fine granular, massive. |
| Crystal system | Orthorhombic - Disphenoidal |
| Cleavage | {001} Perfect, {100} Imperfect |
| Mohs scale hardness | 2.5 |
| Luster | Vitreous, silky in fibrous aggregates |
| Streak | White |
| Diaphaneity | Translucent to translucent |
| Specific gravity | 2.423 - 2.458 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.570 nβ = 1.571 nγ = 1.575 |
| Birefringence | δ = 0.005 |
| Ultraviolet fluorescence | Fluorescent, Short UV:weak white to yellow, Long UV:weak white to yellow |
| References | [1][2][3] |
- Not to be confused with torbernite, a hydrated copper uranyl phosphate.
Tobermorite is a calcium silicate hydrate mineral with chemical formula:
- Ca5Si6O16(OH)2·4H2O
or
- Ca5Si6(O,OH)18·5H2O
Two structural varieties are distinguished: tobermorite-11 Å and tobermorite-14 Å. Tobermorite occurs in hydrated cement paste and can be found in nature as alteration mineral in metamorphosed limestone (e.g. in the Maqarin Area (North Jordan), or in Crestmore (Riverside County, California, USA)) and in skarn.
Tobermorite was first described in 1880 for an occurrence in Scotland, on the Isle of Mull, around the locality of Tobermory.[2]
Crystalline mass of tobermorite.
Use in Roman concrete
Aluminium substituted tobermorite is understood to be a key ingredient in the longevity of ancient Roman undersea concrete, as per the American Ceramic Society.[4]
See also
- Other Calcium silicate hydrate minerals:
- Afwillite
- Clinotobermorite
- Jennite
- Plombierite
- Thaumasite
- Other Calcium aluminium silicate hydrate minerals:
- Hydrogarnet
- Hydrotalcite
References
- American Mineralogist (1954) 39, 1038.
- Abdul-Jaber, Q.H.; Khoury, H. (1998), "Unusual mineralisation in the Maqarin Area (North Jordan) and the occurrence of some rare minerals in the marbles and the weathered rocks", Neues Jahrb. Geol. Paläontol. Abh. 208: 603–629
- Chen, Jeffrey J.; Jeffrey J. Thomas, Hal F.W. Taylor, Hamlin M. Jennings (2004). "Solubility and structure of calcium silicate hydrate". Cement and Concrete Research 34 (9): 1499–1519. doi:10.1016/j.cemconres.2004.04.034. ISSN 0008-8846. Retrieved 2009-02-04.
- Coleman, Nichola J. (2011). "11 Ä tobermorite ion exchanger from recycled container glass". International Journal of Environment and Waste Management 8 (3-4): 366–382. doi:10.1504/IJEWM.2011.042642.
- Currie, J. (1905). "Note on some new localities for gyrolite and tobermorite". Mineralogical Magazine 14: 93–95.
- Eakle, Arthur S. (1927). "Famous mineral localities: Crestmore, Riverside County, California". American Mineralogist 12: 319–321. Retrieved 2009-11-01.
- Kikuma, J.; Tsunashima M., Ishikawa T., Matsuno S., Ogawa A., Matsui K., and Sato M. (2009). "Hydrothermal formation of tobermorite studied by in situ X-ray diffraction under autoclave condition". Journal of Synchrotron Radiation 16: 683–686.
- McConnell, J.D.C. (1954). "The hydrated calcium silicates riversideite, tobermorite and plombierite". Mineralogical Magazine 30: 293–305.
- Merlino, S.; Bonaccorsi E., Armbruster T. (1999). "Tobermorites: Their real structure and order-disorder (OD) character, Sample: 9 Angstrom". American Mineralogist 84: 1613–1621.
- Merlino, S.; Bonaccorsi E., Armbruster T. (2001). "The real structure of tobermorite 11A: normal and anomalous forms, OD character and polytypic modifications (Note: MDO2 - synchrotron radiation source. Locality: Bascenov, Urals, Russia)". European Journal of Mineralogy 13: 577–590.
- Naomichi, Hara (2000). "Formation of jennite and tobermorite from amorphous silica.". J. Soc. Inorg. Mater. Japan 7 (285): 133–142. ISSN 1345-3769. Retrieved 2009-02-04.
External links
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