299— Determining Accuracy of XRD from Known Samples

Powdered x-ray diffraction (XRD) is a technique that has the power to identify minerals and the proportion of the minerals in a mixture. A mineral is defined by a repeatable set of planes between atoms that form the crystal lattice. It is this repetition that allows the process of XRD to work. The process is done by taking a powdered sample and placing it into the machine and then shooting x-rays into the sample causing diffraction. From this using Bragg’s Law we can determine the d-spacing which is how an identity is determined for a sample and the intensity of each angle measured is used for determining proportions of the sample. The samples chosen to test the accuracy were composed of Quartz, K-Feldspar and Hornblende. These were first run as pure samples and then in a variety of mixtures to compare known ratios to XRD-determined ratios.