Per the recommended protocol provided by the instrument manufacturer, we monitored internal instrument stability by measuring Fe K-a counts on a 316 stainless steel coin every day of use. However, standard hXRF models are traditionally used in industry and mining rather than in rigorous geologic analysis, meaning that their calibration algorithms for conversion from raw count data to oxide weight percent data were built from materials with compositions not relevant to most geologic field settings. For this reason we sought to calibrate the instrument against a set of relevant sample standards to determine the instrument’s ability to provide useful geochemical data.