## 3 Results and Discussion
### Mass
Figure 6:0 Transformed mass loss data plot of input energy—“specific mass loss” for both machines combined (data from micro-Deval tests marked blue, data from Los Angeles tests marked orange): (**a**) all data, (**b**) for the energy input scope with data from both machines. 0.012/kJ and 0.0006/kJ for high-energy abrasion (in Los Angeles) and low-energy abrasion (in micro-Deval), respectively. Figure 6:1  
Figure 6:2  
where: \(c\)--abrasion coefficient (\(-\)/kJ). Wear rates, expressed as mass loss per introduced energy (mechanical work) (%/kJ), decreased with energy applied (mechanical work) to abraded material--that is, with each abrasion cycle. Generally, high-energy abrasion wear rates were much higher than low-energy abrasion rates. This can be seen in Figure 10a. Additionally, the change in wear rate is related to the particle shape, but shows the strongest correlation with the angularity (R\({}^{2}\) = 0.88 for micro-Deval, and R\({}^{2}\) = 0.90 for Los Angeles) (Figure 10b). This can be explained by the angular particles experiencing chipping of angular parts faster, contributing to greater mass loss. When roundness increases, there is a smaller presence of angular parts to be chipped off, and a particle is abraded at a slower rate--observed already by [PERSON] [49] in his laboratory experiments in a tumbling mill using angular and rounded clasts. This is also in accordance with the observations of [PERSON] et al. [46], who found that angular particles lose significantly more mass in contrast to rounded ones in a series of two-cycle abrasion tests in a micro-Deval. They studied the influence of fluid in a tumbling test and found greater mass losses of material abraded in water compared to the material abraded in dry conditions. This is definitely a difference between the here-presented dry experiments in the Los Angeles apparatus and the wet experiments in the micro-Deval apparatus, respectively. In this study, the influence of water was acknowledged and taken into account by its mass that contributes to the overall energy (and power) of the abrasion in each setup. [PERSON] and [PERSON] [50], in two-cycle abrasion tests, found higher wear rates in the first cycle when compared to the second abrasion cycle. Similar observations were made by [PERSON] et al. [51]. [PERSON] et al. [52] explained the reduction of wear rates by the asperities becoming rounder, resulting in higher resistance to wear. In contrast, during the low-energy abrasion, wear rates decreased rapidly in the beginning of the abrasion (in the first several cycles). Later on, the wear rate began to change (lower) at a slower rate. It should be noted that in the 10 th and 11 th cycles, one of the particles abraded in single-clast abrasion experiments (micro-Deval) experienced a major breakage, resulting in a considerable fragment being broken off. Consequently, this event contributed to the jump in wear rate values in the 10 th and 11 th cycles. Figure 6:3 Relation between relative residual mass and input energy for both abrasion tests (results from micro-Deval tests marked blue, results from Los Angeles tests marked orange). For the abrasion tests of particle mixtures in the Los Angeles machine, mean grain sizes (d\({}_{50}\)), coefficients of uniformity (C\({}_{\rm U}\)), and coefficients of curvature (C\({}_{\rm C}\)) were determined from particle size distribution curves of the tested material (shown in Figure 11). The initial (at t\({}_{0}\)) mean median grain size d\({}_{50}\) was 51 mm, the mean coefficient of uniformity C\({}_{\rm U}\) = 1.26, and the mean coefficient of curvature C\({}_{\rm C}\) = 0.99. This describes the material as evenly graded [53]. During the first \(\sim\)5 min of rotation (160 rotations), the initial particle size distribution experienced a fast change. During the further abrasion, the change in size slowed down. After the first abrasion cycle in the Los Angeles machine, the mean median grain size dropped to 37.03 mm, the C\({}_{\rm U}\) changed to 5.88, and the C\({}_{\rm C}\) to 2.50.