allophane


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allophane

[′a·lə‚fān]
(geology)
Al2O3·SiO2· n H2O A clay mineral composed of hydrated aluminosilicate gel of variable composition; P2O5 may be present in appreciable quantity.
References in periodicals archive ?
Wada, "Synthetic allophane and imogolite," Journal of Soil Science, vol.
The dominant minerals were smectite (SS), kaolinite (KS), and allophane (AS) in the soils, which were taken, respectively, from the Japanese cities of Isahaya city (32[degrees]50'N, 130[degrees]9'E) in Nagasaki prefecture, and Hukube-cho (35[degrees]3UN, 134[degrees]17'E) and Kotoura-cho (35[degrees]25'N, 133[degrees]39'E) in Tottori prefecture.
However, orthopyroxene, olivine and mangnetite were also detected in contaminated soils including allophane and quartz (Table 2).
'The presence of allophane suggests the volcanic ash spread over a great part of Santa Cruz and Reef Islands in the recent past but that it has since been eroded from the steeply ridged landscapes and remains only on stable, more or less level land as a vestigial cover' (Wall and Hansell 1976:37).
Medium-lustrous blue microcrystals of vauxite form drusy crusts and arcing, hemispherical crests on fragile matrix composed of thin white casts after vanished spheres of--probably--wavellite; in another specimen style from the same find, vibrantly bright blue vauxite druses cover clayey matrix pieces made mostly of allophane. A top-of-the-line vauxite thumbnail could be had here for around $200.
The second highest rate (362 mm h[r.sup.-1]; 14.3 in h[r.sup.-1]) was found in the Hapludands (site 3), the clay fraction of which is made up of allophane and imogolite.
These materials weather rapidly into a material called allophane. Allophane has the unique property of considerable anion exchange capacity.
The fact that the soil samples consists mostly of poorly crystalline allophane and /or halloysite clays plus beta quartz with no ma.
The high allophane content of these volcanic deposits makes them particularly prone to landslides, which occur frequently and rejuvenate the soils.
It is likely that the internal parameters of the model would have to be altered to deal with young volcanic soils that contain significant quantities of allophane.