The behaviour of two types of magnesium stearate with different specific surface areas on granule particles was examined. The magnesium stearate concentration was measured with an energy-dispersive X-ray fluorescence analyser. Different measurement procedures were used to investigate the properties of the two types of magnesium stearate when using different blending times and rotation speeds. Correlations were found between the specific surface area of the magnesium stearate, the blending time, the rotation speed and the specific surface free energy of the excipients. If magnesium stearate has a high specific surface area it shows higher adhesion work and is able to create a very thin homogeneous layer on the surface of the particles. Magnesium concentration was detected with the energy-dispersive X-ray fluorescence analyser. Based on the X-ray investigation the optimum blending time and rotation speed can be determined.