Working with Electron Microprobe Data from a High Pressure Experiment - Calculating Mineral Formulas, Unit Cell Content, and Geothermometry

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This exercise provides students the opportunity to work with real microprobe data to perform a series of common calculations. It also provides a brief glimpse into a high-pressure experiment. (I hope to expand this opportunity in the future via web activities...stay tuned.) The exercise can be used as a laboratory activity or a problem set. It is ideally suited for the use of a spreadsheet like Excel, but can be completed by hand. This is a great opportunity for students who are unfamiliar with spreadsheets to get their feet wet. For me, trial by fire is the best way to learn a new software program. The exercise could be used in any undergraduate petrology or mineralogy course and assumes only a general background in mineral chemistry. The goals are for students to: 1) work with real data from an experiment, 2) learn/remind themselves of the relationship between chemistry and crystal structure as displayed in mineral formula, 3) use a geothermometer to see how phase equilibria can be used to decipher physical properties of rocks. The exercises include: - Mineral formula recalculation - Unit cell content calculation - Calculating end-member percentage - Plotting data on a ternary plot - Geothermometer calculation The exercise could easily be modified to include other "pet" analyses or questions.