An analysis of SI content suggested that the dominating topic was technology. A detailed analysis of the content shows that the majority of papers concern various methods of classification and separation: from screening classification [
1,
2] and sorting [
3], to jig [
4] and flotational [
5] beneficiation, with one publication related to crushing [
6]. Authors applied various methods to monitor the obtained qualitative characteristics [
1,
3] and utilized simulation and modelling tools [
2,
5,
7] in order to evaluate the operation effectiveness of individual separation techniques. Technological aspects were also underlined in a review of recent directions of comminution technology development [
8]. It is accepted that the mechanical processing stage predetermines the efficiency of downstream separation operations, especially in the technological circuits of ore beneficiation. For industries associated with the processing of rock materials, mechanical processing, in turn, directly influences the characteristics of final products in terms of size and shape [
9]. This was the subject of investigations in papers by Saramak, and Gawenda et al. [
4,
8].
Screening technology was the scope in works of N. Duda-Mróz et. al. And C. Yu et. al. [
1,
2]. In the work [
1] focuses on development of diagnostic procedures and monitoring of screening device, particularly its spring, to estimate the time needed for the safe operation of the device and early damage detection. One approach consisted of an analysis of vibration data registered for the specific components of the device, i.e., springs and bearings, and identification of disturbances by means of calculated techniques of wavelet filtering. The second paper, concerning size classification [
2], focuses on the screening of high-viscosity, fine, cohesive particles. The authors analysed the achieved screening efficiency from the scope of the device operation (different sections of the mat surface) and surface energy of particles. The authors also utilized the DEM modelling technique to simulate the behaviour of material on the screen. They also concluded that the service energy level of the particles regarding adhesion was inversely proportional to the screening efficiency. The study of [
3] concerns the sorting technology and investigates the system of Dual-Energy X-ray (DE-XRT) and its ability to distinguish sulphides from non-sulphides. For this type of material, it was possible to achieve a very high accuracy and the system appeared to be an effective sensor that could be used to differentiate sulphides from waste material. The issues presented in this work have an advantage over recent achievements in the development of visual methods and the increasing sensitivity and accuracy of detecting tools [
10]. These methods are significant from the scope of the proper characterization of granular material, especially in its description according to particle size, but also for other features, such as the density, porosity, or content of different types of materials. These issues can be found in paper [
7], where problems concerning granular material segmentation during transportation are analysed. The practical aspects of this work seem to be significant due to the possibility of online monitoring and the early detection of improper or undesired states. The application of neural networks algorithms makes the system more effective. This is especially significant from the scope of material characterization and helps to select and optimize the downstream separation techniques of granular material. Similar aspects were included in the work of [
1]. Optimizational models were also developed in the work of Niedoba et al. [
5], which applied copper ore flotation. A mathematical model based on taxonomic methodology was developed, as well as the adopted functions enabling the determination of the optimal technological parameters of flotation, depending on the material characteristics and process regime. This approach is in line with the popular direction of modelling in mineral processing; assuming the binding of parameters in theoretical models or functions with a material, device, and process course [
2,
8,
9,
11].
Rock materials enrichment is also present in studies concerning the beneficiation of aggregates in a jig device [
4]. This problem is common for a wide group of rock materials, confirming the opinion expressed in other papers of this Special Issue: that the proper characterization of granular material is of key significance in the effective separation of rock materials. The utilization of a patented system of material classification, upstream to the beneficiation, significantly improves separation according to size and shape, but the selection of operational parameters for this system is possible due to the knowledge on the size and shape characteristics of the processed material.
One paper is strictly related to comminution [
7], concerning the problem of material breakage in dynamic conditions. Due to the complexity of this process, resulting from a series of interactions occurring both in space and time, this problem is under constant investigation. This paper’s findings are interesting as they concern the general problem of raw materials breakage, namely the low effective utilization of energy for breakage and high energy-consumption. The results can contribute to a better understanding of selected mechanisms relating to dynamic breakage, such as the probabilities of establishing the given size of particles and their location within the crushed product.