Mineral compositions are reported for Quaternary volcanic rocks of the Matan volcanic center, northern Harrat Rahat, Saudi Arabia. Compositions were measured by wavelength-dispersive methods with the 5-spectrometer JEOL-8900 electron microprobe at the USGS facility in Menlo Park, California; background-corrected X-ray intensities were reduced to oxide weight concentrations with the JEOL proprietary version of the CITZAF reduction schema. These results are part of a collaborative study by the U.S. Geological Survey and Saudi Geological survey to assess the volcanic and seismic hazards associated with the northern Harrat Rahat volcanic field.