Last updated
Crystalline mass of tobermorite
Category Silicate mineral,
Calcium silicate hydrate
(repeating unit)
Ca5Si6O16(OH)2·4H2O, or;
IMA symbol Tbm [1]
Strunz classification 9.DG.10
Crystal system Orthorhombic
Crystal class Disphenoidal (222)
H-M symbol: (2 2 2)
Space group C2221 (no. 20)
Unit cell a = 11.17  Å, b = 7.38 Å
c = 22.94 Å; β = 90°; Z = 4
Formula mass 702.36 g/mol
ColorPale pinkish white, white, brown
Crystal habit As minute laths; fibrous bundles, rosettes or sheaves, radiating or plumose, fine granular, massive.
Cleavage {001} Perfect, {100} Imperfect
Mohs scale hardness2.5
Luster Vitreous, silky in fibrous aggregates
Streak White
Diaphaneity Translucent to translucent
Specific gravity 2.423 – 2.458
Optical propertiesBiaxial (+)
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 [2] [3] [4]

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 an alteration mineral in metamorphosed limestone and in skarn. It has been reported to occur in 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. [3] [5]

Use in Roman concrete

Aluminum-substituted tobermorite is understood to be a key ingredient responsible for the longevity of ancient undersea Roman concrete. The volcanic ash that Romans used for construction of sea walls contained phillipsite, and an interaction with sea water actually caused the crystalline structures in the concrete to expand and strengthen, making that material substantially more durable than modern concrete when exposed to sea water. [6] [7] [8]

Crystal structure of tobermorite: elementary unit cell. Torbermorite CSH 3D Crystal Structure RasMol.gif
Crystal structure of tobermorite: elementary unit cell.

Cement chemistry

Tobermorite is often used in thermodynamical calculations to represent the pole of the most evolved calcium silicate hydrate (C-S-H). According to its chemical formula, its atomic Ca/Si or molar CaO/SiO2 (C/S) ratio is 5/6 (0.83). Jennite represents the less evolved pole with a C/S ratio of 1.50 (9/6).

See also

Related Research Articles

<span class="mw-page-title-main">Wollastonite</span> Single chain calcium inosilicate (CaSiO3)

Wollastonite is a calcium inosilicate mineral (CaSiO3) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or dolomite is subjected to high temperature and pressure, which sometimes occurs in the presence of silica-bearing fluids as in skarns or in contact with metamorphic rocks. Associated minerals include garnets, vesuvianite, diopside, tremolite, epidote, plagioclase feldspar, pyroxene and calcite. It is named after the English chemist and mineralogist William Hyde Wollaston (1766–1828).

<span class="mw-page-title-main">Uvarovite</span> Chromium-bearing garnet group

Uvarovite is a chromium-bearing garnet group species with the formula: Ca3Cr2(SiO4)3. It was discovered in 1832 by Germain Henri Hess who named it after Count Sergei Uvarov (1765–1855), a Russian statesman and amateur mineral collector. It is classified in the ugrandite group alongside the other calcium-bearing garnets andradite and grossular.

<span class="mw-page-title-main">Phillipsite</span> Minerals in the zeolite group

Phillipsite is a mineral series of the zeolite group; a hydrated potassium, calcium and aluminium silicate, approximating to (Ca,Na2,K2)3Al6Si10O32·12H2O. The members of the series are phillipsite-K, phillipsite-Na and phillipsite-Ca. The crystals are monoclinic, but only complex cruciform twins are known, these being exactly like twins of harmotome which also forms a series with phillipsite-Ca. Crystals of phillipsite are, however, usually smaller and more transparent and glassy than those of harmotome. Spherical groups with a radially fibrous structure and bristled with crystals on the surface are not uncommon. The Mohs hardness is 4.5, and the specific gravity is 2.2. The species was established by Armand Lévy in 1825 and named after William Phillips. French authors use the name Christianite (after Christian VIII of Denmark), given by A. Des Cloizeaux in 1847.

<span class="mw-page-title-main">Afwillite</span> Nesosilicate alteration mineral also sometimes found in hydrated cement paste

Afwillite is a calcium hydroxide nesosilicate mineral with formula Ca3(SiO3OH)2·2H2O. It occurs as glassy, colorless to white prismatic monoclinic crystals. Its Mohs scale hardness is between 3 and 4. It occurs as an alteration mineral in contact metamorphism of limestone. It occurs in association with apophyllite, natrolite, thaumasite, merwinite, spurrite, gehlenite, ettringite, portlandite, hillebrandite, foshagite, brucite and calcite.

<span class="mw-page-title-main">Xonotlite</span> Inosilicate mineral

Xonotlite, or eakleite, is a mineral of general formula Ca6Si6O17(OH)2 named by the German mineralogist Karl Friedrich August Rammelsberg in 1866. The name originates from its discovery locality, Tetela de Xonotla, Puebla, Mexico. Although it was discovered in 1866, it was first described in 1959. It is approved by the IMA, but it is a grandfathered species, meaning the name supposedly represents a valid species til this day.

<span class="mw-page-title-main">Ettringite</span> Hydrous calcium sulfo-aluminate

Ettringite is a hydrous calcium aluminium sulfate mineral with formula: Ca6Al2(SO4)3(OH)12·26H2O. It is a colorless to yellow mineral crystallizing in the trigonal system. The prismatic crystals are typically colorless, turning white on partial dehydration. It is part of the ettringite-group which includes other sulfates such as thaumasite and bentorite.

<span class="mw-page-title-main">Thaumasite</span> Complex calcium silicate hydrate mineral

Thaumasite is a calcium silicate mineral, containing Si atoms in unusual octahedral configuration, with chemical formula Ca3Si(OH)6(CO3)(SO4)·12H2O, also sometimes more simply written as CaSiO3·CaCO3·CaSO4·15H2O.

<span class="mw-page-title-main">Roman concrete</span> Building material used in ancient Rome

Roman concrete, also called opus caementicium, was used in construction in ancient Rome. Like its modern equivalent, Roman concrete was based on a hydraulic-setting cement added to an aggregate.

Calcium silicate hydrates are the main products of the hydration of Portland cement and are primarily responsible for the strength of cement-based materials. They are the main binding phase in most concrete. Only well defined and rare natural crystalline minerals can be abbreviated as CSH while extremely variable and poorly ordered phases without well defined stoichiometry, as it is commonly observed in hardened cement paste (HCP), are denoted C-S-H.

<span class="mw-page-title-main">Yuksporite</span>

Yuksporite is a rare inosilicate mineral with double width, unbranched chains, and the complicated chemical formula K4(Ca,Na)14Sr2Mn(Ti,Nb)4(O,OH)4(Si6O17)2(Si2O7)3(H2O,OH)3. It contains the relatively rare elements strontium, titanium and niobium, as well as the commoner metallic elements potassium, calcium, sodium and manganese. As with all silicates, it contains groups of linked silicon and oxygen atoms, as well as some associated water molecules.

<span class="mw-page-title-main">Okenite</span>

Okenite (CaSi2O5·2H2O) is a silicate mineral that is usually associated with zeolites. It most commonly is found as small white "cotton ball" formations within basalt geodes. These formations are clusters of straight, radiating, fibrous crystals that are both bendable and fragile. It also belongs to the family of the calcium silicate hydrates (C-S-H) commonly found in hardened cement paste. In cement chemist notation (CCN) it is noted as CaO·2SiO2·2H2O and abbreviated as CS2H2.

<span class="mw-page-title-main">Jennite</span> Inosilicate alteration mineral in metamorphosed limestone and in skarn

Jennite is a calcium silicate hydrate mineral of general chemical formula: Ca9Si6O18(OH)6·8H2O.

Apachite is a copper silicate mineral with a general formula of Cu9Si10O29·11H2O. The name is associated with the Apache tribe residents of the area near the Christmas copper mine in the Dripping Spring Mountains of Gila County, Arizona, the location where apachite was first described in 1980.

<span class="mw-page-title-main">Fluorellestadite</span> Nesosilicate mineral

Fluorellestadite is a rare nesosilicate of calcium, with sulfate and fluorine, with the chemical formula Ca10(SiO4)3(SO4)3F2. It is a member of the apatite group, and forms a series with hydroxylellestadite.

<span class="mw-page-title-main">Bultfonteinite</span>

Bultfonteinite, originally dutoitspanite, is a pink to colorless mineral with chemical formula Ca2SiO2(OH,F)4. It was discovered in 1903 or 1904 in the Bultfontein mine in South Africa, for which the mineral is named, and described in 1932.

<span class="mw-page-title-main">Junitoite</span> Sorosilicate mineral

Junitoite is a mineral with formula CaZn2Si2O7·H2O. It was discovered at the Christmas mine in Christmas, Arizona, and described in 1976. The mineral is named for mineral chemist Jun Ito (1926–1978).

<span class="mw-page-title-main">Gyrolite</span> Rare phyllosilicate mineral crystallizing in spherules

Gyrolite, NaCa16(Si23Al)O60(OH)8·14H2O, is a rare silicate mineral (basic sodium calcium silicate hydrate: N-C-S-H, in cement chemist notation) belonging to the class of phyllosilicates. Gyrolite is also often associated with zeolites. It is most commonly found as spherical or radial formations in hydrothermally altered basalt and basaltic tuffs. These formations can be glassy, dull or fibrous in appearance.

<span class="mw-page-title-main">Garronite-Ca</span> Zeolite mineral

Garronite-Ca is a fairly rare silicate mineral, from the zeolite, which has been found in a few dozen locations in the world. It was first found in the Glenariff Valley, Garron Plateau, County Antrim, Northern Ireland, and in some locations in Iceland. The name comes from the town of Garron, in Northern Ireland, which is consequently considered its type locality. The name initially used was that of Garronite, without subfixes, but the discovery in 2015 of a garronite with dominant sodium instead of calcium in the position of interchangeable cations made it necessary to use subfixes, remaining as Garronite-Ca, to distinguish it from the new species, Garronite-Na.

<span class="mw-page-title-main">Tacharanite</span> Calcium aluminium silicate hydrate mineral

Tacharanite is a calcium aluminium silicate hydrate (C-A-S-H) mineral of general chemical formula Ca12Al2Si18O33(OH)36 with some resemblance to the calcium silicate hydrate (C-S-H) mineral tobermorite. It is often found in mineral assemblage with zeolites and other hydrated calcium silicates.


  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  2. Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Tobermorite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 27 July 2022.
  3. 1 2 Mineralogy Database, , retrieved 27 July 2022
  4. Barthelmy, David (2014). "Lavendulan Mineral Data". Retrieved 27 July 2022.
  5. Scottish physician and amateur mineralogist Matthew Forster Heddle (1828–1897) first described tobermorite in: Heddle (1880). "Preliminary notice of substances which may prove to be new minerals. Part second". Mineralogical Magazine and Journal of the Mineralogical Society. 4: 117–123. doi:10.1180/minmag.1880.004.18.04. See pp. 119–121.
  6. Ancient Romans made world’s ‘most durable’ concrete. We might use it to stop rising seas, Washington Post , Ben Guarino, July 4, 2017. Retrieved July 5, 2017.
  7. Ancient lessons: Roman concrete durable, green, Jim Destefani, ed., Ceramic Tech Today, The American Ceramic Society, June 7, 2013
  8. Jackson, Marie D.; Mulcahy, Sean R.; Chen, Heng; Li, Yao; Li, Qinfei; Cappelletti, Piergiulio; Wenk, Hans-Rudolf (2017). "Phillipsite and Al-tobermorite mineral cements produced through low-temperature water-rock reactions in Roman marine concrete". American Mineralogist. 102 (7): 1435–1450. Bibcode:2017AmMin.102.1435J. doi: 10.2138/am-2017-5993CCBY . ISSN   0003-004X.

Further reading