Tobermorite Group
A group of related mineral species
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About Tobermorite Group
Formula:
Ca4+x(AlySi6-y)O15+2x-y · 5H2O
Member of:
A new nomenclature scheme for minerals in the Tobermorite Supergroup and tobermorite group was approved by the IMA in 2014 (Biagioni et al, 2018). The tobermorite group consists of a calcium silicate hydrate series having a basal spacing of ∼11 Å and an orthorhombic sub-cell symmetry. Its general formula is Ca4+x(AlySi6–y)O15+2x–y·5H2O. Its endmember compositions correspond to tobermorite Ca5Si6O17·5H2O (x = 1 and y = 0) and kenotobermorite, Ca4Si6O15(OH)2·5H2O (x = 0 and y = 0). Al-rich samples do not warrant a new name, because Al can only achieve a maximum content of 1/6 of the tetrahedral sites (y = 1).
The members of the Tobermorite group differ in their thermal behaviour which can be ‘‘normal’’ (the phase shrinks to a 9 Å phase at 300°C) or ‘‘anomalous’’ (the phase preserves its 11 Å basal spacing at 300°C).
The structure contains composite layers consisting of infinite sheets of (CaO7) polyhedra, to both sides of which wollastonite-type dreier single chains of (SiO4) tetrahedra are attached, running along the b-axis. Those layers are stacked along the c axis and linked by Si-O-Si bonds between the single chains in adjacent layers, forming dreier double chains whose individual strands belong to different layers. The open channels running along the b axis between the layers are occupied either by water molecules, resulting in the formula Ca4(H2Si6O17)·5H2O (anomalous tobermorite) or by both water molecules and Ca2+ ions, resulting in the formula Ca4.5(HSi6O17)·5H2O (normal tobermorite). Upon heating, the water molecules are lost, and the structure is rearranged in order to fulfill the coordination requirements of the interlayer calcium ions.
The structure of clinotobermorite, which also shrinks upon heating, is very closely related to that of normal tobermorite (Merlino et al., 2001).
Compare also the related xonotlite.
Tobermorite group compounds are well known in the cement industry as C-S-H compounds. They form when cement reacts with water and play an important role in the binding process.
The members of the Tobermorite group differ in their thermal behaviour which can be ‘‘normal’’ (the phase shrinks to a 9 Å phase at 300°C) or ‘‘anomalous’’ (the phase preserves its 11 Å basal spacing at 300°C).
The structure contains composite layers consisting of infinite sheets of (CaO7) polyhedra, to both sides of which wollastonite-type dreier single chains of (SiO4) tetrahedra are attached, running along the b-axis. Those layers are stacked along the c axis and linked by Si-O-Si bonds between the single chains in adjacent layers, forming dreier double chains whose individual strands belong to different layers. The open channels running along the b axis between the layers are occupied either by water molecules, resulting in the formula Ca4(H2Si6O17)·5H2O (anomalous tobermorite) or by both water molecules and Ca2+ ions, resulting in the formula Ca4.5(HSi6O17)·5H2O (normal tobermorite). Upon heating, the water molecules are lost, and the structure is rearranged in order to fulfill the coordination requirements of the interlayer calcium ions.
The structure of clinotobermorite, which also shrinks upon heating, is very closely related to that of normal tobermorite (Merlino et al., 2001).
Compare also the related xonotlite.
Tobermorite group compounds are well known in the cement industry as C-S-H compounds. They form when cement reacts with water and play an important role in the binding process.
Unique Identifiers
Mindat ID:
39598
Long-form identifier:
mindat:1:1:39598:6
Chemistry of Tobermorite Group
Mindat Formula:
Ca4+x(AlySi6-y)O15+2x-y · 5H2O
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0006887 | Kenotobermorite | Merlino S, Bonaccorsi E, Armbruster T (2001) The real structure of tobermorite 11A: normal and anomalous forms, OD character and polytypic modifications European Journal of Mineralogy 13 577-590 | 2001 | Bascenov, Urals, Russia | 0 | 293 | |
| 0006886 | Kenotobermorite | Merlino S, Bonaccorsi E, Armbruster T (2001) The real structure of tobermorite 11A: normal and anomalous forms, OD character and polytypic modifications European Journal of Mineralogy 13 577-590 | 2001 | Bascenov, Urals, Russia | 0 | 293 | |
| 0006885 | Kenotobermorite | Merlino S, Bonaccorsi E, Armbruster T (2001) The real structure of tobermorite 11A: normal and anomalous forms, OD character and polytypic modifications European Journal of Mineralogy 13 577-590 | 2001 | Wessels mine, South Africa | 0 | 293 | |
| 0006884 | Kenotobermorite | Merlino S, Bonaccorsi E, Armbruster T (2001) The real structure of tobermorite 11A: normal and anomalous forms, OD character and polytypic modifications European Journal of Mineralogy 13 577-590 | 2001 | Wessels mine, South Africa | 0 | 293 | |
| 0006833 | Tobermorite | Merlino S, Bonaccorsi E, Armbruster T (2000) The real structure of clinotobermorite and tobermorite 9 A: OD character, polytypes, and structural relationships European Journal of Mineralogy 12 411-429 | 2000 | 0 | 293 | ||
| 0002330 | Tobermorite | Merlino S, Bonaccorsi E, Armbruster T (1999) Tobermorites: Their real structure and order-disorder (OD) character American Mineralogist 84 1613-1621 |  | 1999 | 0 | 293 | |
| 0002329 | Tobermorite | Merlino S, Bonaccorsi E, Armbruster T (1999) Tobermorites: Their real structure and order-disorder (OD) character American Mineralogist 84 1613-1621 | | 1999 | 0 | 293 |
CIF Raw Data - click here to close
Relationship of Tobermorite Group to other Species
Member of:
Other Members of Tobermorite Supergroup:
| Clinotobermorite | Ca5Si6O17 · 5H2O | Mon. |
| Paratobermorite | Ca5AlSi5O16(OH) · 5H2O | Mon. 2/m |
| Plombièrite | Ca5Si6O16(OH)2 · 7H2O | Orth. |
| Riversideite | Ca5Si6O16(OH)2 · 2H2O | Orth. |
Tobermorite Group Members:
| Kenotobermorite | Ca4Si6O15(OH)2 · 5H2O | Mon. |
| Tobermorite | Ca5Si6O17 · 5H2O | Mon. 2 : P21 |
Minerals structurally related to group:
| 'Jennite' | Ca9(Si3O9)2(OH)8 · 8H2O |
Minerals chemically related to group:
| 'Xonotlite' | Ca6(Si6O17)(OH)2 |
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 Tobermorite Group
mindat.org URL:
https://www.mindat.org/min-39598.html
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References for Tobermorite Group
Reference List:
McConnell, J. D. C. (1954) The hydrated calcium silicates riversideite, tobermorite, and plombierite. Mineralogical Magazine and Journal of the Mineralogical Society, 30 (224) 293-305 doi:10.1180/minmag.1954.030.224.02
Merlino, Stefano, Bonaccorsi, Elena, Armbruster, Thomas (1999) Tobermorites; their real structure and order-disorder (OD) character. American Mineralogist, 84 (10) 1613-1621 doi:10.2138/am-1999-1015
Merlino, Stefano, Bonaccorsi, Elena, Armbruster, Thomas (2000) The real structures of clinotobermorite and tobermorite 9 Å: OD character, polytypes, and structural relationships. European Journal of Mineralogy, 12 (2) 411-429 doi:10.1127/0935-1221/2000/0012-0411
Localities for Tobermorite Group
Showing 154 localities.
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The Locality List
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(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.
Buer, Bjørkedalen, Porsgrunn, Telemark, Norway