While in the process of drilling a bolt hole, when a piece of rock fell from the roof ,striking the canopy of the roof bolter and a piece 12""X 10""X 1-0"" struck right hand's ring finger causing an avulsion of the of the skin from the very tip of finger. EE finger was caught between the rock and the tray on the roof bolter. No bone damage. Started Missing work on 10/12/18