Intensities and wavelengths of the K-series lines of silicon were measured using primary excitation in the electron probe. Specifically, intensity and line Position data for the Si K spectral lines α1, α2, ß, α3, and α4 were recorded using a high-resolution continuously curved mica-crystal vacuum spectrometer. Spectra were obtained from silicon metal and a wide range of mineral samples, e.g., SiO2, Mg2Si2O6, CaSiO3, KAlSi2O6, CaMgSi2O6, KAlSi3O8, NaAlSi3O8, CaAl2Si2O8, Fe2SiO4, and (Na, K) (AI, Si)2O4. Only slight differences were found to exist among the mineral spectra, but these differed markedly from that obtained from silicon metal.