Air classification is widely used in industry for fractionation of crushed materials. Simplicity and high efficiency at low energy costs are distinguished by air classifiers with an inclined louver grille. The relevance of the work is conditioned upon the fact that it conducted an experimental and theoretical study of these devices on a model material – quartzite, which retains its density regardless of size. Through an experimental and theoretical study on a model material, quartzite, this work aims to investigate air classifiers with an inclined louver grille and propose a mathematical model that can reduce the amount of preliminary work required for calculating industrial classifiers. In the process of mathematical modelling, two tasks were solved: calculating the velocity field of two-dimensional vortex-free air flows inside the classifier and the subsequent study of particle motion in these fields. To set the correct boundary conditions of the problem, a thermomagnetometry was made and experimental studies of air velocities at the defining points of the classifier were carried out. A model of the distribution of extracted particles along the height of the classifier is suggested. A comparison of theoretical calculations with experimental data at different speeds and consumption concentrations showed satisfactory agreement. This study provides valuable insights into the separation properties of air classifiers with an inclined louver grille, specifically on a model material, quartzite. By conducting both experimental and theoretical studies, the authors were able to develop a mathematical model that accurately predicts air classification indicators for various materials. The results of this study have significant prospects in the industry, as it can potentially reduce the time and cost required for conducting preliminary laboratory studies on small copies of devices for specific types of raw materials.