The paper discusses abrasive water-jet cutting of hard-to-cut materials represented by high carbon steel DIN norm No.1.2436 (CSN EN 19437) plate 61–mm-thick and high-strength concrete cube sized 150 mm. Four relatively hard minerals with different densities not commonly used in water-jet technology were tested and their cutting results compared to those of three types of almandine garnets: Ukraine, Australian, and sorted Australian. Cutting efficiency was evaluated utilizing declination angle. Dependence of cutting efficiency on abrasive density and hardness was investigated. High density of abrasive appeared to be disadvantageous in our experiment. Cutting efficiency dependence on hardness exhibited nearly linear course, the increase was much more significant for concrete than for steel. Evaluation of experimental results led to the conclusion that cutting mechanism in case of very thick samples is different from common abrasive waterjet cutting. The limit declination angle for thick samples is significantly smaller, it was found to be approximately 22°. This result represents entirely new finding. The most promising finding from the economical point of view appears to be behavior of corundum, when cutting concrete. Our experimental results promise 20 % increase in cutting speed for brittle materials.