BULK VERSUS POWDER X-RAY DIFFRACTION (XRD) COMPARISONS FOR PHASE COMPOSITION AND QUANTITATIVE ANALYSIS (RIETVELD) WITH FOUR ROCK AND MINERAL TYPES: AMPHIBOLE, MARBLE, AUGITE, AND SHALE

Since geologists began using X-ray diffraction (XRD) to determine/confirm mineral phases in 1924, it has commonly been referred to as X-ray powder diffraction. The popular practice is to grind or powder the specimen before measuring. The intent is to randomize the individual crystals in a poly-crystalline material and minimize the particle size. This usually results in higher diffraction peak intensity in counts, higher peak to background ratios and helps minimize preferred orientation effects. However, could any valuable information be obtained from the bulk form XRD measurements without all the grinding?

A series of XRD experiments with four rock and mineral types are compared for both the bulk and powdered forms to determine what types of information can be observed or “lost” in each physical preparation method. Results from each preparation method are compared from automatic phase identification, and quantification (Rietveld analysis)programs, along with average crystallite size. Weight percents of each phase are mass balanced against Wave Dispersive X-Ray Fluorescence results from Rigaku's new Mineral-Pak analyses for confirmation.