A micro-mechanical part made of insulating material, such as a silicon balance spring (1) for a timepiece movement, tends to adhere to a neighboring part when it is in movement, such as the balance cock (9). This drawback is removed by carrying out, over all or part of the surface, a thin deposition of a layer of conductive material, such as a metal, which is preferably non-oxidizing and non-magnetic, such as gold, platinum, rhodium or silicon.