Gibbsite, Al(OH)3, is one of the mineral forms of aluminium hydroxide. It is often designated as γ-Al(OH)3[2]: 2 (but sometimes as α-Al(OH)3.[3]). It is also sometimes called hydrargillite (or hydrargyllite).
Gibbsite is an important ore of aluminium in that it is one of three main phases that make up the rock bauxite.
Gibbsite has three named structural polymorphs or polytypes: bayerite (designated often as α-Al(OH)3,[2]: 2 but sometimes as β-Al(OH)3)[citation needed], doyleite, and nordstrandite. Gibbsite can be monoclinic or triclinic, while bayerite is monoclinic.[2]: 13 Doyleite and nordstrandite are triclinic forms.[2]: 13
The structure of gibbsite is interesting and analogous to the basic structure of the micas. The basic structure forms stacked sheets of linked octahedra. Each octahedron is composed of an aluminium ion bonded to six hydroxide groups, and each hydroxide group is shared by two aluminium octahedra.[4] One third of the potential octahedral spaces are missing a central aluminium. The result is a neutral sheet: with aluminium as a +3 ion and hydroxide a –1 ion, the net cationic charge of one aluminium per six hydroxides is (+3)/6 = +1/2, and likewise the net anionic charge of one hydroxide per two aluminium atoms is (-1)/2 = -1/2. The lack of a charge on the gibbsite sheets means that there is no charge to retain ions between the sheets and act as a "glue" to keep the sheets together. The sheets are only held together by weak residual bonds and this results in a very soft easily cleaved mineral.[citation needed]
Gibbsite's structure is closely related to the structure of brucite, Mg(OH)2. However the lower charge in brucite's magnesium (+2) as opposed to gibbsite's aluminium (+3) does not require that one third of the octahedrons be vacant of a central ion in order to maintain a neutral sheet. The different symmetry of gibbsite and brucite is due to the different way that the layers are stacked.
It is the gibbsite layer that in a way forms the "floor plan" for the mineral corundum, Al2O3. The basic structure of corundum is identical to gibbsite except the hydroxides are replaced by oxygen. Since oxygen has a charge of -2 the layers are not neutral and require that they must be bonded to other aluminiums above and below the initial layer producing the framework structure that is the structure of corundum.
Gibbsite is interesting for another reason because it is often found as a part of the structure of other minerals. The neutral aluminium hydroxide sheets are found sandwiched between silicate sheets in important clay groups: the illite, kaolinite, and montmorillonite/smectite groups. The individual aluminium hydroxide layers are identical to the individual layers of gibbsite and are referred to as the gibbsite layers.[5]
The lattice parameters for gibbsite depending upon the particular method used to measure or calculate them and are therefore displayed as ranges below. An Al-Al interlayer spacing of 0.484 or 0.494 nm has been reported.[6]
^ abcdefWefers, Karl; Misra, Chanakya (1987). Oxides and hydroxides of aluminum. Alcoa Research Laboratories. OCLC 894928306.
^N.N. Greenwood and A. Earnshaw, "Chemistry of Elements", 2nd edition, Butterworth and Heinemann, 1997
^Saalfeld, H.; Wedde, M. (1974). "Refinement of the crystal structure of gibbsite, Al(OH)3" (PDF). Zeitschrift für Kristallographie. 139 (1–2): 129–135. Bibcode:1974ZK....139..129S. doi:10.1524/zkri.1974.139.1-2.129.
^Advances in catalysis. Amsterdam. 24 November 2014. pp. 321–325. ISBN978-0-12-800300-8. OCLC 894277485.{{cite book}}: CS1 maint: location missing publisher (link)
^Gale, Julian D.; Rohl, Andrew L.; Milman, Victor; Warren, Michele C. (2001). "An ab Initio Study of the Structure and Properties of Aluminum Hydroxide: Gibbsite and Bayerite". The Journal of Physical Chemistry B. 105 (42): 10236–10242. doi:10.1021/jp011795e. ISSN 1520-6106.
Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., ISBN0-471-80580-7
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September 26, 2023
gibbsite, mineral, forms, aluminium, hydroxide, often, designated, sometimes, also, sometimes, called, hydrargillite, hydrargyllite, generalcategoryhydroxide, mineralsformula, repeating, unit, 3ima, symbolgbb, strunz, classification4, 10crystal, systemmonoclin. Gibbsite Al OH 3 is one of the mineral forms of aluminium hydroxide It is often designated as g Al OH 3 2 2 but sometimes as a Al OH 3 3 It is also sometimes called hydrargillite or hydrargyllite GibbsiteGibbsiteGeneralCategoryHydroxide mineralsFormula repeating unit Al OH 3IMA symbolGbb 1 Strunz classification4 FE 10Crystal systemMonoclinicCrystal classPrismatic 2 m same H M symbol Space groupP21 mIdentificationMohs scale hardness2 5 3Specific gravity2 35Ball and stick model of the part of the crystal structure of gibbsiteGibbsite is an important ore of aluminium in that it is one of three main phases that make up the rock bauxite Gibbsite has three named structural polymorphs or polytypes bayerite designated often as a Al OH 3 2 2 but sometimes as b Al OH 3 citation needed doyleite and nordstrandite Gibbsite can be monoclinic or triclinic while bayerite is monoclinic 2 13 Doyleite and nordstrandite are triclinic forms 2 13 Contents 1 Structure 2 Mineralogical Properties 3 Etymology 4 References 5 Further readingStructure EditThe structure of gibbsite is interesting and analogous to the basic structure of the micas The basic structure forms stacked sheets of linked octahedra Each octahedron is composed of an aluminium ion bonded to six hydroxide groups and each hydroxide group is shared by two aluminium octahedra 4 One third of the potential octahedral spaces are missing a central aluminium The result is a neutral sheet with aluminium as a 3 ion and hydroxide a 1 ion the net cationic charge of one aluminium per six hydroxides is 3 6 1 2 and likewise the net anionic charge of one hydroxide per two aluminium atoms is 1 2 1 2 The lack of a charge on the gibbsite sheets means that there is no charge to retain ions between the sheets and act as a glue to keep the sheets together The sheets are only held together by weak residual bonds and this results in a very soft easily cleaved mineral citation needed Gibbsite s structure is closely related to the structure of brucite Mg OH 2 However the lower charge in brucite s magnesium 2 as opposed to gibbsite s aluminium 3 does not require that one third of the octahedrons be vacant of a central ion in order to maintain a neutral sheet The different symmetry of gibbsite and brucite is due to the different way that the layers are stacked It is the gibbsite layer that in a way forms the floor plan for the mineral corundum Al2O3 The basic structure of corundum is identical to gibbsite except the hydroxides are replaced by oxygen Since oxygen has a charge of 2 the layers are not neutral and require that they must be bonded to other aluminiums above and below the initial layer producing the framework structure that is the structure of corundum Gibbsite is interesting for another reason because it is often found as a part of the structure of other minerals The neutral aluminium hydroxide sheets are found sandwiched between silicate sheets in important clay groups the illite kaolinite and montmorillonite smectite groups The individual aluminium hydroxide layers are identical to the individual layers of gibbsite and are referred to as the gibbsite layers 5 The lattice parameters for gibbsite depending upon the particular method used to measure or calculate them and are therefore displayed as ranges below An Al Al interlayer spacing of 0 484 or 0 494 nm has been reported 6 Gibbsite Structural Properties Crystal System Molecules Per Unit Cell Lattice parameters nm Lattice Angles a b cMonoclinic 7 4 0 850 0 868 0 487 0 508 0 922 0 974 92 8 94 5Triclinic 2 13 16 1 733 1 008 0 973 94 2 92 1 90 0Mineralogical Properties EditIndex of Refraction 2 12 a b g1 568 1 568 1 587Etymology EditGibbsite is named after George Gibbs 1776 1833 an American mineral collector 8 References Edit 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 a b c d e f Wefers Karl Misra Chanakya 1987 Oxides and hydroxides of aluminum Alcoa Research Laboratories OCLC 894928306 N N Greenwood and A Earnshaw Chemistry of Elements 2nd edition Butterworth and Heinemann 1997 Saalfeld H Wedde M 1974 Refinement of the crystal structure of gibbsite Al OH 3 PDF Zeitschrift fur Kristallographie 139 1 2 129 135 Bibcode 1974ZK 139 129S doi 10 1524 zkri 1974 139 1 2 129 Gibbsite on Galleries com Advances in catalysis Amsterdam 24 November 2014 pp 321 325 ISBN 978 0 12 800300 8 OCLC 894277485 a href Template Cite book html title Template Cite book cite book a CS1 maint location missing publisher link Gale Julian D Rohl Andrew L Milman Victor Warren Michele C 2001 An ab Initio Study of the Structure and Properties of Aluminum Hydroxide Gibbsite and Bayerite The Journal of Physical Chemistry B 105 42 10236 10242 doi 10 1021 jp011795e ISSN 1520 6106 Gibbsite Mineral Data on Webmineral comFurther reading EditHurlbut Cornelius S Klein Cornelis 1985 Manual of Mineralogy 20th ed ISBN 0 471 80580 7 nbsp Wikimedia Commons has media related to Gibbsite Retrieved from https en wikipedia org w index php title Gibbsite amp oldid 1140082505, wikipedia, wiki, book, books, library,
