We report on electron emission and defect formation in the interaction between slow (v~;0.3 vBohr) highly charged ions (SHCI) with insulating (type IIa) and semiconducting (type IIb) diamonds. Electron emission induced by 31Pq+ (q=5 to 13), and 136Xeq+ (q=34 to 44) with kinetic energies of 9 kVxq increase linearly with the ion charge states, reaching over 100 electrons per ion for high xenon charge states without surface passivation of the diamond with hydrogen. Yields from both diamond types are up to a factor of two higher then from reference metal surfaces. Crater like defects with diameters of 25 to 40 nm are formed by the impact of single Xe44+ ions. High secondary electron yields and single ion induced defects enable the formation of single dopant arrays on diamond surfaces.