Gyrolite, NaCa₁₆(Si₂₃Al)O₆₀(OH)₈·14H₂O, is a rare

silicate mineral Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

(basic sodium calcium silicate hydrate: N-C-S-H, in

cement chemist notation Cement chemist notation (CCN) was developed to simplify the formulas cement chemists use on a daily basis. It is a shorthand way of writing the chemical formula of oxides of calcium, silicon, and various metals. Abbreviations of oxides The ma ...

) belonging to the class of

phyllosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consid ...

s. Gyrolite is also often associated with

zeolites Zeolites are microporous, crystalline aluminosilicate materials commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula ･y where is either a metal ion or H+. These p ...

. It is most commonly found as spherical or radial formations in hydrothermally altered

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...

and basaltic tuffs. These formations can be glassy, dull or fibrous in appearance. Gyrolite is also known as ''centrallasite'', ''glimmer zeolite'' or ''gurolite''.

Discovery and natural occurrence

It was first described in 1851 for an occurrence at The Storr on the Isle of Skye,

Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...

and is named from the ancient Greek word for circle, ''guros'' (γῦρος), based on the round form in which it is commonly found. Minerals associated with gyrolite include

apophyllite The name apophyllite refers to a specific group of phyllosilicates, a class of minerals. Originally, the group name referred to a specific mineral, but was redefined in 1978 to stand for a class of minerals of similar chemical makeup that compris ...

, okenite and many of the other

. Gyrolite is found in Scotland, Ireland; Italy, Faroe Islands, Greenland, India, Japan, USA, Canada and various other localities.

Occurrence in hardened cement paste and concrete

Gyrolite is also mentioned as a rare

calcium silicate hydrate Calcium silicate hydrate (or C-S-H) is the main product of the hydration of Portland cement and is primarily responsible for the strength in cement based materials (e.g. concrete). Preparation When water is added to cement, each of the compounds ...

( C-S-H) phase in cement chemistry textbooks with a simplified formulation: Ca₈(Si₄O₁₀)₃(OH)₄ · ~6 H₂O, which is consistent with the general formulation given here above, but does not consider the

isomorphic substitution In mathematics, an isomorphism is a structure-preserving Map (mathematics), mapping between two Mathematical structure, structures of the same type that can be reversed by an inverse function, inverse mapping. Two mathematical structures are iso ...

of one

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...

atom by one

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

and one

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

atoms in its crystal lattice. Gyrolite may form at higher temperature in oilwell cement muds containing

ground granulated blast furnace slag Ground-granulated blast-furnace slag (GGBS or GGBFS) is obtained by quenching molten iron slag (a by-product of iron and steel-making) from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into ...

s (

GGBFS Ground-granulated blast-furnace slag (GGBS or GGBFS) is obtained by quenching molten iron slag (a by-product of iron and steel-making) from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into ...

) activated by alkali. It could also form in CEM III cement-based

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

exposed to alkali-silica reaction (ASR) at elevated temperature.

Hydrothermal synthesis

Gyrolite can be synthesized in the laboratory, or industrially, by hydrothermal reaction in the temperature range 150 – 250 °C by reacting CaO and amorphous SiO₂, or

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

, in saturated steam in the presence of CaSO₄ salts or not. At temperature lower than 150 °C, the reaction rate is very slow. At temperature above 250 °C, gyrolite recrystallizes into 1.13 nm

tobermorite 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 cemen ...

and

xonotlite Xonotlite, or eakleite, is a mineral of general formula 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 i ...

. Gyrolite is also one of the rare phases detected in situ along with

pectolite Pectolite is a white to gray mineral, Na Ca2 Si3 O8(O H), sodium calcium hydroxide inosilicate. It crystallizes in the triclinic system typically occurring in radiated or fibrous crystalline masses. It has a Mohs hardness of 4.5 to 5 and a specif ...

by synchrotron X-rays diffraction in hydrothermal synthesis of cement. Synthetic gyrolite has also a large specific surface and could enter industrial applications as oil absorber. Gyrolite globular rosettes resemble that of shlykovite, a new natural crystalline C-S-H mineral characterized in 2010 and also to mountainite and rhodesite, other crystalline ASR products of the same family.

Discovery and natural occurrence

Occurrence in hardened cement paste and concrete

Hydrothermal synthesis

See also

References

Further reading