Abstract: The transformation of kaolinite to halloysite-7 Å was identified in the kaolin deposit of São Vicente de Pereira (SVP), using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Both the 02,11 and 13,13 reflections show changes in the XRD patterns along the kaolinite to halloysite-7 Å transition, and the FTIR spectra show changes corresponding to both OH− and Si-O-stretching bands and Al-O-Si-bending vibrations. The interlayer water content in the kaolinite structure increases during transition. The two-layer periodicity of well-ordered kaolinite and rolling up of kaolinite plates are observed using high-resolution transmission electron microscopy (HRTEM). Long and short tubes exhibit halloysite-7 Å. No structural Fe was found in the kaolinite samples. Analytical electron microscopy (AEM) indicates no substitution of Al3+ for Si4+. The Si/Al ratio shows values of ∼ 1 for the kaolinite and rolled kaolinite plates. The 27Al magic angle spinning neutron magnetic resonance (MAS-NMR) spectra display a resonance centered at ∼ 1 ppm, assigned to six-coordinated aluminum. The transformation of kaolinite to halloysite-7 Å is controlled by surface reaction.