Samples were analyzed using the handheld portable X-ray fluorescence (pXRF) analyzer as part of a study examining the occurrence chromium and of natural and anthropogenic hexavalent Chromium, Cr(VI) in groundwater. Data will be used to estimate naturally-occurring background Cr(VI) concentrations upgradient, near the plume margins, and downgradient from a mapped Cr(VI) contamination plume near Hinkley, CA (Izbicki and Groover, 2016). Relative concentrations for 18 elements of interest were measured on the less than 2mm and sized- fraction splits of the 36 field samples. Greater than 20 percent of the samples analyzed using pXRF also have Contract Laboratory results for comparison. These pXRF results are part of a data release including grain size distribution, photographic, and associated chemical and mineral analysis data for 36 sediment core and alluvium samples as well as Scanning Electron Microscopy analyses on select grains from magnetic and heavy mineral separates collected near Hinkley, CA. The cooperator for this study is the Lahontan Regional Water Quality Control Board.