The behaviour of a powder impacted on a target depends on its size, its particle size distribution (PSD), the material mechanical properties and the industrial rig. A methodology for the study of impact in an air jet mill allows one to evaluate the relation between the impact energy and the grindability of the impacted solids. Moreover, the behaviour of an impacted powder is determined by its process conditions. An example is given with the study of different hydrargillites and aluminas produced in different ways and having different morphologies. The impact test allows one to classify these solids with grindability and attrition criteria. Morphological analysis relates them to external structural descriptors.