Imogolite

Al₂SiO₃(OH)₄IMA symbolImo^[1]Strunz classification9.ED.20Crystal systemTetragonal
Unknown space groupIdentificationColorWhite, blue, green, brown, blackCrystal habitConchoidal to earthy masses of microscopic threadlike particles and bundles of fine tubes, each about 20 Å in diameterMohs scale hardness2–3LusterVitreous, resinous, waxyDiaphaneityTransparent to translucentSpecific gravity2.7Optical propertiesIsotropicRefractive indexn=1.47–1.51References^[2][3][4]

Imogolite is an aluminium silicate clay mineral with the chemical formula Al₂SiO₃(OH)₄. It occurs in soils formed from volcanic ash and was first described in 1962 for an occurrence in Uemura, Kumamoto prefecture, Kyushu Region, Japan.^[2] Its name originates from the Japanese word imogo, which refers to the brownish yellow soil derived from volcanic ash. It occurs together with allophane, quartz, cristobalite, gibbsite, vermiculite and limonite.^[3]

Imogolite consists of a network of nanotubes with an outer diameter of ca. 2 nm and an inner diameter of ca. 1 nm. The tube walls are formed by continuous Al(OH)₃ (gibbsite) sheets and orthosilicate anions (O₃SiOH groups). Owing to its tubular structure, natural availability, and low toxicity, imogolite has potential applications in polymer composites, fuel gas storage, absorbents, and as a catalyst support in chemical catalysis.^[5]

References

Further reading

• Media related to Imogolite at Wikimedia Commons
• Wada K, Yoshinaga N (1969). "The structure of "Imogolite"" (PDF). Am. Mineral. 54: 50–71.
• Gabriel JC, Davidson P (2003). "Mineral Liquid Crystals from Self-Assembly of Anisotropic Nanosystems" (PDF). Topics in Current Chemistry. 226: 126–127. doi:10.1007/b10827. Archived from the original (PDF) on 2011-07-26. (Contains structure illustration)