<jats:title>Abstract</jats:title><jats:p>Although structural disorder in kaolinite has been investigated extensively, it is still not understood properly. To investigate the problem, a kaolinite specimen of sedimentary origin from Capim, Brazil, was examined, mainly by transmission electron microscopy (TEM). Selected-area electron diffraction (SAED) along the <jats:italic>X</jats:italic><jats:sub>i</jats:sub> ([100], [110], and [<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0009860400035795_inline1.png" />]) directions shows various features, from completely discrete patterns to heavily streaked ones along the <jats:italic>c</jats:italic>* direction, suggesting that the degree of stacking disorder is variable among individual grains. High-resolution TEM images indicate that stacking faults are mainly caused by disorder of alternating <jats:italic>t</jats:italic><jats:sub>1</jats:sub> (~ −<jats:italic>a</jats:italic>/3) and <jats:italic>t</jats:italic><jats:sub>2</jats:sub> (−<jats:italic>a</jats:italic>/3 +<jats:italic>b</jats:italic>/3) layer displacements. Furthermore, stacking faults have been observed (1) as isolated stacking faults (<jats:italic>e.g.</jats:italic> insertion of an isolated <jats:italic>t</jats:italic><jats:sub>2</jats:sub> `fault' in an ordered sequence with <jats:italic>t</jats:italic><jats:sub>1</jats:sub> layer displacement) and (2) as interstratification of two kinds of multilayer blocks having regular <jats:italic>t</jats:italic><jats:sub>1</jats:sub> and <jats:italic>t</jats:italic><jats:sub>2</jats:sub> layer displacements. A mixture of grains with various degrees and modes of disorder with alternating <jats:italic>t</jats:italic><jats:sub>1</jats:sub> and <jats:italic>t</jats:italic><jats:sub>2</jats:sub> layer displacements may explain the experimental profile of the 02, 11 X-ray diffraction band.</jats:p><jats:p>Faults related to displacement of the octahedral vacancy and/or to layer rotation were also observed in HRTEM images. The SAED patterns along the <jats:italic>Y</jats:italic><jats:sub>i</jats:sub> ([010], [310], and [<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S0009860400035795_inline2.png" />]) directions occasionally have extra spots and/or streaks, suggesting the presence of stacking sequences with (±60°, 180°) mutual layer rotation and/or with (0, ±<jats:italic>b</jats:italic>/3) layer displacements. The local dickite or nacrite-like fragments formed by these faults are in qualitative agreement with recent low-temperature FTIR results from this sample, where distinct ν(OH) absorption bands reflect multiple interlayer O-H⋯O environments that are possibly ascribed to dickite and nacrite.</jats:p>