There are few effective methods for characterizing the molecular scale structural environments of Ca2+ in hydrated cements, which has limited our ability to understand the structure of, for example, Ca-silicate hydrate (C-S-H). Ca-43 nuclear magnetic resonance (NMR) spectroscopy has long been considered too insensitive to provide useful data in this regard, but Ca-43 magic angle spinning (MAS) NMR spectra reported here for synthetic tobermorite and jennite with naturally abundant levels of Ca-43 demonstrate that this is a viable approach. We show that spectra with useful signal/noise ratios can be obtained in a reasonable acquisition period (similar to 2 days) using an H-0 field strength of 21.1 T, 5 mm rotors spinning at a frequency of 5 kHz, and a double frequency sweep preparatory pulse sequence. Tobermorite and jennite produce relatively broad resonances due to their complex structures and structural disorder, however, the chemical shift differences between six-coordinate Ca-43 in jennite and seven-coordinate Ca-43 in 11 angstrom tobermorite are large enough that the signals are entirely resolved at this field. These data suggest that signal from ideal tobermorite-like and jennite-like sites in cement C-S-H can most likely be distinguished by Ca-43 NMR and that this method will be a powerful approach for studying cement-based ceramic materials in the coming decade.