Non destructive observation by X-ray diffraction on a berlinite crystal

For the characterisation of a crystal, several non destructive observations can be made by X-Ray diffraction. The crystal may be studied either as a block as grown from the autoclave or as a cut or a finished resonator. Once the crystal is placed on a special piezogoniometer its orientation may be measured and its orientation matrix calculated. Then, the most useful lattices planes are chosen, some of them allow the determination of the lattice parameters, others the detection of defects as twins or a mosaic structure. Illustrations are made on a berlinite crystal showing some macroscopic defects