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[[Image:halloytemcx.jpg|right|thumb|200px|TEM Image of Halloysite Nanotubules]] |
[[Image:halloytemcx.jpg|right|thumb|200px|TEM Image of Halloysite Nanotubules (''unknown scale - see discussion pages'')]] |
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[[Image:Mineraly.sk - halloyzit.jpg|right|thumb|200px|A sample of Halloysite]] |
[[Image:Mineraly.sk - halloyzit.jpg|right|thumb|200px|A sample of Halloysite (''unknown scale - see discussion pages'')]] |
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'''Halloysite''' is a 1:1 aluminosilicate [[clay]] [[mineral]] with the [[empirical formula]] Al<sub>2</sub>Si<sub>2</sub>O<sub>5</sub>(OH)<sub>4</sub>. Its main constituents are [[aluminium]] (20.90%), [[silicon]] (21.76%), and [[hydrogen]] (1.56%). Halloysite typically forms by [[hydrothermal]] alteration of alumino-silicate minerals. <ref>Paul F. Kerr, FORMATION AND OCCURRENCE OF CLAY MINERALS, Clays and Clay Minerals, Volume 1, page 19-32, 1952</ref> It can occur intermixed with [[dickite]], [[kaolin]], [[montmorillonite]] and other clay minerals. [[X-ray diffraction]] studies are required for positive identification. It was first described in 1826 and named for the [[Belgian]] [[geologist]] [[Omalius d'Halloy]]. |
'''Halloysite''' is a 1:1 aluminosilicate [[clay]] [[mineral]] with the [[empirical formula]] Al<sub>2</sub>Si<sub>2</sub>O<sub>5</sub>(OH)<sub>4</sub>. Its main constituents are [[aluminium]] (20.90%), [[silicon]] (21.76%), and [[hydrogen]] (1.56%). Halloysite typically forms by [[hydrothermal]] alteration of alumino-silicate minerals. <ref>Paul F. Kerr, FORMATION AND OCCURRENCE OF CLAY MINERALS, Clays and Clay Minerals, Volume 1, page 19-32, 1952</ref> It can occur intermixed with [[dickite]], [[kaolin]], [[montmorillonite]] and other clay minerals. [[X-ray diffraction]] studies are required for positive identification. It was first described in 1826 and named for the [[Belgian]] [[geologist]] [[Omalius d'Halloy]]. |
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Halloysite is a 1:1 aluminosilicate clay mineral with the empirical formulaAl2Si2O5(OH)4. Its main constituents are aluminium (20.90%), silicon (21.76%), and hydrogen (1.56%). Halloysite typically forms by hydrothermal alteration of alumino-silicate minerals. [1] It can occur intermixed with dickite, kaolin, montmorillonite and other clay minerals. X-ray diffraction studies are required for positive identification. It was first described in 1826 and named for the Belgian geologist Omalius d'Halloy.
Two common forms are found, when hydrated the clay exhibits a 1 nm spacing of the layers and when dehydrated (meta-halloysite) the spacing is 0.7 nm. Halloysite naturally occurs as small cylinders which average 30 nm in diameter with lengths between 0.5 and 10 micrometres. [2]
Halloysite has been found at Australia, Austria, Belgium, Bolivia, Canada, China, Colombia, Czech Republic, France, Germany, Greece, Greenland, Hungary, Ireland, Israel, Italy, Japan, Kazakhstan, Madagascar, Mexico, Netherlands, New Zealand, Norway, Oman, Russia, Slovak Republic, South Korea, Spain, Sweden, Switzerland, Tajikistan, Turkmenistan, UK, USA and Zimbabwe. [3]
A very pure halloysite is mined from an highly altered rhyolite occurrence in New Zealand uses include porcelain, bone and fine china. Various patents exist for the use of hallosyite as nanofillers [4] and in controlled release technology for a range of active agents.[5][6] It is also used for other high-tech ceramic applications.
Halloysite also has been used as a petroleum cracking catalyst in the past, [7]. Exxon has also developed a cracking catalyst based on synthetic halloysite[8].
Due to its structure, it can be used as filler in either natural or modified forms in nanocomposites.
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