Aluminosilicate

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

s ( IMA symbol: Als) are minerals composed of

aluminium 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. I ...

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 ...

, and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

, plus countercations. They are a major component of

kaolin Kaolinite ( ) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahedral ...

and other clay minerals.

Andalusite Andalusite is an aluminium nesosilicate mineral with the chemical formula Al2SiO5. This mineral was called andalousite by Delamétehrie, who thought it came from Andalusia, Spain. It soon became clear that it was a locality error, and that the spe ...

kyanite Kyanite is a typically blue aluminosilicate mineral, found in aluminium-rich metamorphic pegmatites and sedimentary rock. It is the high pressure polymorph of andalusite and sillimanite, and the presence of kyanite in metamorphic rocks gener ...

, and

sillimanite Sillimanite is an aluminosilicate mineral with the chemical formula Al2SiO5. Sillimanite is named after the American chemist Benjamin Silliman (1779–1864). It was first described in 1824 for an occurrence in Chester, Connecticut. Occurrence ...

are naturally occurring aluminosilicate minerals that have the composition Al₂ Si O₅. The

triple point In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.. It is that temperature and pressure at which the sub ...

of the three polymorphs is located at a temperature of and a pressure of . These three minerals are commonly used as

index mineral An index mineral is used in geology to determine the degree of metamorphism a rock has experienced. Depending on the original composition of and the pressure and temperature experienced by the protolith (parent rock), chemical reactions between mine ...

s in

metamorphic rock Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...

s. Naturally occurring

microporous A microporous material is a material containing pores with diameters less than 2 nm. Examples of microporous materials include zeolites and metal-organic frameworks. Porous materials are classified into several kinds by their size. The reco ...

, hydrous aluminosilicate minerals are referred to as

zeolite 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 ...

Feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) felds ...

is a common

tectosilicate 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 ...

aluminosilicate mineral made of potassium, sodium, and calcium cations surrounded by a negatively charged network of silicon, aluminium and oxygen atoms. The catalyst

silica-alumina Amorphous silica-alumina is a synthetic substance that is used as a catalyst or catalyst support. Julius Scherzer, Adrian J. Gruia, (1996), ''Hydrocracking Science and Technology'', CRC Press, It can be prepared in a number of ways for example: * ...

is an amorphous substance which is not an aluminosilicate compound.

Aluminosilicate glasses

There exist a wide variety of glass types. The characteristics of these different types depend on the chemical composition of the glass, with a special focus on the oxide composition. Glasses can be categorized into many different groups, one of them including the so-called aluminosilicate glasses.

Properties

Aluminosilicate glasses can be formulated to tolerate temperatures up to , temperatures substantially above those of

borosilicate glass Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), m ...

es and comparable to ceramic materials, with maximum temperatures being determined by the material's transformation temperature. Their formulations can also be matched to the thermal expansion coefficients of

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials d ...

s, e.g. molybdenum, making possible the creation, via hot-forming processes, of extremely tight gas-proof glass to metal seals.

Alkaline earth aluminosilicate glasses

Characteristically, these glasses are free of alkali oxides and contain 15–25% Al₂O₃, 52–60% SiO₂ and about 15% alkaline earths. Very high transformation temperatures and softening points are typical features. Main fields of application are glass bulbs for

halogen lamps A halogen lamp (also called tungsten halogen, quartz-halogen, and quartz iodine lamp) is an incandescent lamp consisting of a tungsten filament sealed in a compact transparent envelope that is filled with a mixture of an inert gas and a smal ...

, high-temperature thermometers and thermally and electrically highly loadable film resistors.

Alkali aluminosilicate glasses

The Al₂O₃ content of alkali aluminosilicate glasses is typically 10–25% and the alkali content over 10%. The high alkali content prepares the glass for ion exchange with bigger alkali ions in order to improve the surface compressive strength. Due to this particular feature, this glass type is especially suitable for the use in touch displays, solar cells cover glass and laminated safety glass. High transformation temperatures and outstanding mechanical properties, e.g. hardness and scratch behavior, are characteristic of this glass type.

References

Glass compositions Nesosilicates {{mineral-stub

Aluminosilicate glasses

Properties

Alkaline earth aluminosilicate glasses

Alkali aluminosilicate glasses

See also

References