When I do granite the dark areas are not touched by the laser beam and the light or white/ grey areas are the ones hit by the beam, correct? So the detail in the shaded in between area depends on the dithering or spacing of those dots. It could be and just guessing the space between the dots, the beam goes off and then does not come on fast enough or at enough power. To prove, I would try slowing down the speed a little at a time until you get that detail Do some testing on some scape pieces or purchase some at Home Depot. . I have no idea of the power and speeds your running but it does not take a whole lot of power to do granite.... at least what I have seen anyway.