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Al2Si2O5(OH)4 (halloysite) multiwalled nanotubes (MWNTs) were synthesized for the first time using a simple hydrothermal preparation technique involving the reaction SiO2 + Al(OH)3 in the presence of 0.1-0.2 mole fraction GeO2 substituted for SiO2. The inclusion of small amounts of Ge(IV) into the Al2Si2O5(OH)4 structure together with the creation of Si(IV) vacancies stimulates curving of layered nanosheets, such that they scroll to form spheroids, and finally tubes. At 0.5 GeO2 substitution, small single-walled imogolite-type nanotubes (SWNTs) with the Al2SixGe1-xO3(OH)4 structure are formed instead alongside x-ray amorphous particles. Thus the substitution of GeO2 for SiO2 provides a direct method to control the morphology of nanostructured aluminosilicates.