Using Powder X-ray Diffraction in the Undergraduate Curriculum to Determine Total Iron in Rocks and Minerals

Abstract

We developed a simple X-ray diffraction (XRD) method to measure the iron content of rocks and minerals up to 10 weight percent Fe (total iron as Fe) which can be used routinely in undergraduate mineralogy and petrology courses. The method is based on the linear relationship between powder X-ray fluorescence intensity background and the wt% Fe in the sample. Using analytical rock standards with known total iron contents G-2, GSP-1, AGV-1, BCR-1, W-l and Or-1, we established a calibration curve by plotting the X-ray fluorescence intensity background against wt% total Fe. We tested the method using several rock samples with known total Fe contents and found that it predicts the iron content of samples with an accuracy of ± 10 wt% of the amount present. It is very easy to teach undergraduate students how to use this technique and to develop lab exercises where they can test different hypotheses based on iron content of rock samples.