Feldspar Mineral Chemistry Using the FCAEM Remotely Operable Electron Probe Micro-Analyzer.

Jaime Macdonald Florida Gulf Coast University (FGCU) and Sven Holbik Florida International University (FIU)

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This page first made public: Aug 17, 2015

Summary

This lab uses the remote operation of an Electron Probe Micro-Analysis (EPMA) available through the Florida Center for Analytical Electron Microscopy (FCAEM; https://fcaem.fiu.edu/), at Florida International University, Miami, to explore feldspar mineral chemistry. This lab explores detailed mineral chemistry, data normalization, and plotting compositional ranges on ternary diagrams suitable as an introductory assignment in a Mineralogy, Earth Materials, or Petrology course. This instructor-led interactive demonstration of remote Electron Microprobe use introduces students to microprobe analysis, x-ray analytical techniques, standardization, image analysis, normalization, mineral formulas and composition. The instructor can acquire images (optional) of samples containing feldspar (provided by FCAEM or instructor's samples) then select multiple points for analysis. This activity captivates student's attention and provides a hands-on instrument-led approach to introducing undergraduate students to chemical analysis and vital concepts in mineralogy and petrology.

Mineral Analysis, Mineralogy | College Introductory, College Lower (13-14), College Upper (15-16)

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Context

Audience

This assignment is intended for sophomore to senior level course in Mineralogy, Earth Materials, or Petrology. It could also be adapted for an introductory courses if needed. Since this is an instructor-led assignment (one collection event on electron microprobe) which can be projected onto a large screen, there is no real limit to class size.

Skills and concepts that students must have mastered

How the activity is situated in the course

Goals

Content/concepts goals for this activity

The objective of this assignment is to familiarize students with electron probe microanalysis, x-ray analytical techniques, mineral formulas/associations and compositions and examining data quality. The assignment is designed using Excel to normalize data and calculate end member compositions. The instructor should spend time in class refreshing student's skills with Excel commands. The higher order thinking skills for this assignment include having students scrutinize collected data, calculating mineral components, and understanding possible ionic substitution.

Higher order thinking skills goals for this activity

Other skills goals for this activity

Description and Teaching Materials

Feldspar Mineral Formula & Normalization (Microsoft Word 2007 (.docx) 2.3MB Aug14 15)

Instructors Key with EPMA data and Ternary Diagram (Excel 2007 (.xlsx) 43kB Aug14 15)

EPMA Remote Startup Procedures (Acrobat (PDF) 308kB Aug14 15)

EPMA General Operational Procedures (Acrobat (PDF) 2.1MB Aug14 15)

Teaching Notes and Tips

The demonstration should take between 30 to 45 minutes from acquiring images, digitizing points, setting up standards and finally analyzing 5 to 20 points. Normally, one class period is used to introduce students to the EPMA system and collect the data then assign the problem set as a lab during the following class meeting. Alternatively, it can be assigned for homework. Remote users of the EPMA can use the in-house samples at FCAEM or mail in their own samples for analysis. The EPMA software is initially challenging, so if you are a first time user plan to use the instrument at least one time with FCAEM staff supervision (via phone, Skype, or TeamViewer) to get comfortable with the controls. We encourage faculty users to check out our step-by-step procedures on our website https://fcaem.fiu.edu/tutorials/. This activity is building upon the SERC Undergraduate Research Across the Curriculum Case Study by Jeff Ryan, University of South Florida (http://serc.carleton.edu/NAGTWorkshops/undergraduate_research/casestudy/electron_microprobe.html)

Assessment

The questions and answers in this assignment are straightforward and based on data collected so if the students have correctly answered questions and scrutinized the data then the objective of the assignment has been met. Pre- and post-testing using the Creative Exercises assessment of Lewis et al. (2010; Journal of College Science Teaching) was used to assess this active learning assignment by the instructors.

References and Resources

Florida Center for Analytical Electron Microscopy
A Term Research Project Focused on Electron Microprobe Studies of Unknowns in a Junior-Level Mineralogy/Petrology Course; Jeff Ryan, University of South Florida; http://serc.carleton.edu/NAGTWorkshops/undergraduate_research/casestudy/electron_microprobe.html
Lewis, S.E., Shaw, J. L., and Freeman, K. A., 2010, Creative Exercises in General Chemistry: A Student-Centered Assessment: Journal of College Science Teaching, v. 40, No. 1, p. 48-53.

Video tutorials at https://fcaem.fiu.edu/tutorials/

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