X-Ray diffraction (XRD) data for bulk sediment and clay separations taken from cores from Bristol Dry Lake, California and geothermal springs from Paoha Island (Mono Lake), California. The data were collected for two separate projects: (1) determining the source of lithium in Bristol Dry Lake (BDL), and (2) determining the mechanism of sinter formation on Paoha Island, Mono Lake. The data from BDL were collected in collaboration with Standard Lithium Ltd. who drilled 6 new proprietary wells in 2017 and 2018 on the playa. The wells were not cored, but cuttings were available for sampling a few months after the drilling was completed. The wells were up to 1500 feet deep. Cuttings were kept in the dark in sealed plastic bags in a storage container on site at ambient temperatures. The Paoha Island samples were part of a larger study conducted by the National Research Program of the Water Mission Area to look at the role of microbes in arsenic utilization and growth. The current substudy was to look at how microbes may or may not contribute to sinter growth and preservation at the geothermal springs where the microbes live.