Sharp silicon tips, coated with diamond, were tested concerning electron gun application. Emission stability, reproducibility of current-voltage characteristics, and beam confinement in the vacuum of 10(-6) Torr were studied. No hysteresis or shift of emission characteristics during long term testing have been found. Low frequency current fluctuations were less than 10%. The electron source was tested over a 120 h period and the current decrease was within 10% of the initial value at the end of the test period. The divergence half-angle of emitted electrons was found to be within 3 degrees.