A poorly crystallized (i.e., lacks long-range atomic order) hydrous aluminosilicate of approximate composition of (OH)3Al2O3SiOH, with a natural-samples range of Al2(OH)3(SiO2)1.0-1.2(H2O)2.3-3.0. The Si/Al ratio is near 0.5. The structure consists of nanotubes, often occurring in closest packing arrangements about 2nm in diameter and to several micrometers in length, typically forming bundles 10 to 30 nm across. The morphology makes imogolite potentially useful in industry for contaminant sorption, gas storage, as an oxidation catalyst, and as an electron emitter. Imogolite has a gibbsite-like structure with Si tetrahedra spanning the vacant octahedral sites, and because of the mismatch in size between the vacant site and the tetrahedron, the gibbsite-like sheet rolls. Imogolite forms from weathered volcanic ash, but may also occur in podzolized soils and in pumice.
Cf., allophane