Three industrial materials: bentonite, barite and pyrophyllite were investigated regarding their suitability as fillers in plastic compounds. Two Bulgarian calcium bentonites had to be transformed (“alkali-activated”) into sodium bentonites. The montmorillonite content, the “Swelling Index”, as well as an X-Ray diffraction analysis (XRD) were chosen as suitability indicators. The montmorillonite content was 55 - 58 %, the swelling index was 21 ml / 2g and additional minerals such as albite occurred in large quantities (25 %). The low montmorillonite content in connection with the low Swelling Index indicates that the two bentonites are not suitable as active filler for plastics. For possible further applications, e.g. drilling bentonite, rheological properties were tested, resulting in a viscometer dial reading at 600 rpm R600 = 11 and a plastic viscosity ratio b = 2.4. The Bosnian barite was characterized by mineralogical aspects and processed by optical, gravity, magnetic and electrostatic separation methods. The raw material was medium grained and intergrown with quartz and tetrahedrite. The brightness varied between 96 % and 73 %. SrSO4 contents differed between the samples in the range of 0.7 – 17 %. The manual optical sorting resulted in a barite recovery of 87 %. The sink-float analysis in three particle size ranges <1 mm showed a degree of liberation of > 99 % for barite. The shaking table test resulted in a barite grade of 98 % with a recovery of 81 %. The suitability as a filler in plastics may apply. Two Bosnian pyrophyllites were mineralogically investigated and processed by attrition and flotation. The mineral processing products were characterized by acid solubility, loss on ignition (LOI), brightness measurements and XRD. As accessory minerals quartz and carbonates occurred. Heavy minerals were apatite and zircon. The least amount of acid-soluble minerals (1.29 %) and the least LOI (3.95 %) were reached by flotation. The brightness of the raw material (81 % and 72 %) could not be increased. The suitability as a filler in plastics is not given regarding these particular results, due to the high quantity of additional minerals.