A rock drill (1) for cutting rock comprising an elongated, helical shaft (2), which has, at one end, an insertion part (3) and, at the end opposite, a tool head (4) with cutters (5) made of hard material, wherein the helical shaft (2) is at least partially coated with a colored layer (7a, 7b) and the layer forms a lengthwise running wear indicator marking (8) inside the helical groove (8).