X-ray diffraction analysis is performed employing the instrument calibration verified by NBS and NIST standard reference samples (e.g. Si XRD NBS standards #640 and #640a), in addition to unique mixtures of standards that are implemented for custom applications to ensure analytical accuracy and precision.
The XRD lab is a participant in interlaboratory quality assurance efforts, including the biannual Reynolds Cup organized by the Clay Mineral Society.
XRD Lab Standard Mixtures
For QA/QC purposes, the XRD lab prepares standard mixtures from clay minerals (smectite, illite/smectite, kaolinite, chlorite, and illite) and non-clay minerals (quartz, dolomite, calcite, feldspar, siderite, marcasite, pyrite, etc.), all common mineral phases that occur in sediments, clay ores, and soils. Source material for clay minerals used in standard mixtures are prepared and purified by the Source Clays of the Clay Mineral Society. Additional QA/QC standards are chosen from the suite appropriate RM and NIST standards. These standard concentrations are well known and historically reported, making them essential for QA/QC evaluation of quantitative, semi-quantitative, and Rietveld methods.
The Reynolds Cup
The Reynolds Cup competition was established in 2000 and named after Prof. Robert C. Reynolds, Jr., a pioneer in quantitative clay mineralogy and a great contributor to clay science. It is a quantitative mineralogical analysis competition that is free and open to any laboratory in a commercial, industrial, government, and academic field. It is held by the Clay Minerals Society and organized every two years by the winner of the previous event. Each participant is sent three mixtures of pure standards representing realistic sedimentary rock compositions and can use any method or combination of methods to obtain the most accurate quantitative phase analysis. It is an effective evaluation of various XRD methods applied to clay mineral-bearing samples. Our XRD laboratory is honored to participate in the 10th Anniversary of the Reynolds Cup competition.