Abstract: Silcretes developed within the in situ regolith in the Barr Smith Range, Western Australia, were investigated using optical and electron-beam techniques. One of the cementing agents in these silcretes showed gel-like optical properties and had a variable aluminosilicate chemical composition at the scale of electron microprobe analysis so that it might he considered as allophane-like material High resolution transmission electron microscopy demonstrated that the material consists of a fine-grained and poorly ordered kaolinite embedded in a matrix of amorphous silica.