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Buer, Bjørkedalen, Porsgrunn, Telemark, Norway
© OT. Ljostad 2005
|System:||Orthorhombic||Colour:||White, light pink|
There are three structural variants known: Tobermorite-9 Å (= Riversideite), Tobermorite-11 Å (= Tobermorite sensu stricto) and Tobermorite-14 Å (= Plombièrite).
"Tobermorite-10 Å" is Oyelite.
Some specimens of Tobermorite-11 Å shrink on dehydration and are called "normal tobermorite", while others do not shrink and are therefore called "anomalous".
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).
Tobermorite has been redefined by IMA in 2014 as two minerals: tobermorite and kenotobermorite.
NOTE: All localities listed here under "tobermorite" should be checked if they are to be assigned to tobermorite or kenotobermorite
May appear visually similar to Tacharanite.
The CSH-phases (calcium-silicate-hydrate phases) in hardened cement mostly consist of tobermorite-like phases, often poorly crystalline.
Classification of Tobermorite
|IMA status:||Redefined Approved 2014|
|Strunz 8th edition ID:||8/F.19-20|
|Nickel-Strunz 10th (pending) edition ID:||9.DG.10|
9 : SILICATES (Germanates)
D : Inosilicates
G : Inosilicates with 3-periodic single and multiple chains
|Dana 8th edition ID:||188.8.131.52|
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
3 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with 3-, 4-, or 5-membered rings and 8-membered rings
|Hey's CIM Ref.:||14.5.23|
14 : Silicates not Containing Aluminum
5 : Silicates of Ca
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Type Occurrence of Tobermorite
|Type Locality:||Tobermory, Isle of Mull, Strathclyde (Argyllshire), Scotland, UK|
|Year of Discovery:||1880|
Physical Properties of Tobermorite
|Colour:||White, light pink|
Crystallography of Tobermorite
|Cell Parameters:||a = 11.17Å, b = 7.38Å, c = 22.94Å|
β = 90°
|Ratio:||a:b:c = 1.514 : 1 : 3.108|
|Unit Cell Volume:||V 1,891.05 Å³ (Calculated from Unit Cell)|
|X-Ray Powder Diffraction:|
Optical Data of Tobermorite
|RI values:||nα = 1.570 nβ = 1.571 nγ = 1.575|
|Maximum Birefringence:||δ = 0.005|
Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
|Dispersion:||r > v|
Chemical Properties of Tobermorite
|Simplified for copy/paste:||[Ca4Si6O17)·2H2O]·(Ca·3H2O)|
|Essential elements:||Ca, H, O, Si|
|All elements listed in formula:||Ca, H, O, Si|
Relationship of Tobermorite to other Species
|Member of:||Tobermorite Group|
|Other Members of Group:|
|Related Minerals - Nickel-Strunz Grouping):|
|Related Minerals - Hey's Index Grouping:|
Other Names for Tobermorite
|Health Warning:||No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.|
References for Tobermorite
Currie, J. (1905). Note on some new localities for Gyrolite and Tobermorite. Mineralogical Magazine, 14, 93-95.
McConnell, J.D.C. (1954), The hydrated calcium silicates riversideite, tobermorite and plombierite, Mineralogical Magazine: 30: 293-305.
American Mineralogist (1954): 39: 1038.
Megaw, H.D., and Kelsey, C.H. (1956): Crystal Structure of Tobermorite. Nature 177, 390-391.
Hamid, S.A. (1981): The crystal structure of the 11Å natural tobermorite Ca2.25[Si307.5(OH)1.5].1 H20. Zeitschrift für Kristallographie 154, 189-198.
American Mineralogist (1999): 84: 1613-1621.
Merlino, S., Bonaccorsi, E., and Armbruster, T. (2001): The real structure of tobermorite-11Å: normal and anomalous forms, OD character and polytypic modifications. European Journal of Mineralogy 13(3), 577-590.
J. Kikuma, M. Tsunashima, T. Ishikawa, S. Matsuno, A. Ogawa, K. Matsui and M. Sato (2009): Hydrothermal formation of tobermorite studied by in situ X-ray diffraction under autoclave condition. J. Synchrotron Rad. 16, 683-686.
Internet Links for Tobermorite
|Specimens:||The following Tobermorite specimens are currently listed for sale on minfind.com.|
Localities for Tobermorite
The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
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