Calcite is a common mineral phase found in pure and mixed phase systems. The data reported here was collected for comparison with data collected on other systems and to determine the relative sensitivity for various Ca photopeaks that we were using for the analysis of other Ca-containing mineral phases. This data was collected on a PHI Quantum Scanning ESCA Microprobe. This instrument is unique in that the x-ray beam is focused and can be scanned over the sample. A single crystal of calcite was broken in vacuum (exposing the 101¯4 cleavage plane) and analyzed using monochromatic AlKαx-rays. The sample was neutralized using both low energy ions and electrons.