Summary: A nondestructive method for sodium-trace determination is described. 16 quartz samples widely distributed over the Swiss Alps have been investigated. The sodium contents have been measured after irradiation with 3,6 • 1012slow n/cm2, sec by γ-spectrometry. Concentrations of 0,15 to 24 ppm (i.e. sodium quantities of 0,03 to 5 μg in this case) have been found. The considerable spread of results demonstrates the different conditions of formation of the quartz crystals.