Small object shape of cylinder maybe 1'x 2' suddenly appeared directly over us about 100' above. we were on mountain top and we could see it until it cleared the top of the hill next to us. speed seemed to be as fast as a rocket, so only had seconds to view object. nothing like a drone or bird, more like a rock with no light trail or fire. just dull grey object flying straight line not up or down. waited to hear a crash noise but heard nothing and saw nothing after it flew over next hill.