Tobermorite

Tobermorite
Crystalline mass of tobermorite
General
Category	Silicate mineral, Calcium silicate hydrate
Formula (repeating unit)	Ca5Si6O16(OH)2·4H2O, or; Ca5Si6(O,OH)18·5H2O
Strunz classification	9.DG.10
Crystal system	Orthorhombic
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 symmetry	Orthorhombic - disphenoidal H-M symbol (2 2 2)
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 and in skarn. It has been reported from the Maqarin Area of north Jordan and in the Crestmore Quarry near Crestmore Heights, Riverside County, California.

Tobermorite was first described in 1880 for an occurrence in Scotland, on the Isle of Mull, around the locality of Tobermory.^[2]

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]

Crystal structure of tobermorite: elementary unit cell

See also

• Other Calcium silicate hydrate minerals:
  • Afwillite
  • Jennite
  • Thaumasite

References

1. Handbook of Mineralogy
2. Mindat.org
3. Webmineral data
4. Ancient lessons: Roman concrete durable, green, Jim Destefani, ed., Ceramic Tech Today, The American Ceramic Society, June 7, 2013

• 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, pp. 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. doi:10.1180/minmag.1905.014.64.06.
• 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.; Sato M. (2009). "Hydrothermal formation of tobermorite studied by in situ X-ray diffraction under autoclave condition". Journal of Synchrotron Radiation 16: 683–686. doi:10.1107/s0909049509022080.
• McConnell, J.D.C. (1954). "The hydrated calcium silicates riversideite, tobermorite and plombierite". Mineralogical Magazine 30: 293–305. doi:10.1180/minmag.1954.030.224.02.
• 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. doi:10.1127/0935-1221/2001/0013-0577.
• 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

• Tobermorite in the American Mineralogist Crystal Structure Database