Automated Diffraction Tomography (ADT)
The structures of three different minerals (beryl, sanidine, labradorite) were structurally characterised via transmission electron microscopy, especially focusing on the application of the method Automated Diffraction Tomography (ADT). Thereby it was possible to record 3D diffraction data of single crystallites and domains on a nanometre scale which could be used for structure analysis. For beryl and sanidine the structure was solved on single particles from powdered samples. In case of labradorite the origin of the schiller was described over several magnitudes. In order to observe the structural context in detail, ion-thinned samples along several orientations were required. The orientation of the lamellae producing the schiller was described in relation to the axes of the cell and the obtained specimen. Furthermore, the size of the lamellae was correlated with the wavelength of the reflected light and thus, the colour of the labradorescence as well as the An-content. A structural characterisation was performed on the basic metric of the labradorite cell followed by a characterisation of the modulated lattice. Additionally, the satellite vector and its length were determined. The full analysis of the positions of reflection was complicated further by twinning on different scales.
A)  zone-axis taken from the 3d reconstructed labradorite cell. Incommensurate modulation induces satellite reflections along c* which are not described by the lattice.
B)Bright field TEM image of labradorite lamellae.