To investigate particle motions and resultant impact erosion is highly desirable to improve the abrasive waterjet and abrasive airjet micro-machining performance. Numerical study found that particles in waterjet are easier to move following water streamlines than that in airjet due to their larger momentum equilibration numbers, and average impact angle induced by micro-particles in airjet are larger than that driven by waterjet, which in turn affect the resultant impact erosion on quartz crystals. By experimentally analysing the surface morphology of eroded craters generated by the individual micro-particle laden waterjet and airjet, brittle erosion mode is found to significantly dominate the impact erosion of quartz crystal driven by airjet, while both of brittle and ductile erosion modes can be observed by the impacts of the micro-particle laden waterjet. Particularly with relatively low water pressure contributions of ductile and brittle erosions to the material removal process are found to be equally important. (C) 2019 Elsevier B.V. All rights reserved.