An updated X-ray diffractogram library of geologic materials

The X-ray diffraction (XRD) pattern library presented here is intended for qualitative or quantitative mineralogical analysis of geologic materials. The original collection of 169 reference diffractograms was released by Eberl (2003) as a part of RockJock, a USGS program for quantitative analysis of mineralogy, which included patterns of many of the major rock-forming minerals needed to analyze a wide variety of rocks, sediments, soils, and other geologic materials. The library was generated from mineral samples collected from the environment or synthesized in the laboratory. In the case of geologic samples, every effort was made to collect as pure a mineral specimen as possible. The purpose of this data release is to update the patterns in the mineral library and to provide details of a modified sample preparation procedure. Modifications to the original method include using a corundum spike for reference intensity ratio (RIR) determination, and adding an additional mixing step to reduce preferred orientation in a powder XRD mount. Scanning electron microscope (SEM) and XRD data are also included from a synthetic mineral mixture prepared for powder X-ray diffraction analysis both with and without the additional mixing step. In addition, several new patterns have been added to the original mineral library, including several synthetic and natural poorly crystalline materials (iron and aluminum minerals, basaltic glass, and organic materials). REFERENCES Eberl, D.D., 2003, User guide to RockJock - A program for determining quantitative mineralogy from X-ray diffraction data: USGS Open-File Report 2003-78, 47 p., https://doi.org/10.3133/ofr200378.