Introduction to the SEM/EDS or "Every Composition Tells a Story"

John T Cheney and Peter D. Crowley
,
Amherst College
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Summary

This lab is designed as an introduction to the investigation of minerals with the Scanning Electron Microscope (SEM) and the X-ray analyzer (Energy Dispersive Spectrometer - EDS). We will explore the relationships among the optical image, the backscattered electron image, and the chemical composition of minerals in thin-sections that we have studied optically. Specifically we will examine the interaction of a mineral with a high energy (20 kv) electron beam focused to a diameter of a few microns. Three different detectors of the SEM/EDS will be used to study minerals in thin sections. Additional concepts that may be introduced in this lab include: formula calculations, solid solution, exsolution, and chemical zoning.

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Context

Audience

This activity is designed for an undergraduate required course in mineralogy and is generally for sophomore or junior level students.

Skills and concepts that students must have mastered

  • Petrographic microscopy

How the activity is situated in the course

This activity is a stand-alone exercise, but is part of a larger volume of classroom and laboratory activities from "Teaching Mineralogy," a workbook published by the Mineralogical Society of America, Brady, J., Mogk, D. W., and Perkins, D., (editors), 1997,406 pp.

Goals

Content/concepts goals for this activity

In this activity, students will examine the interaction of a mineral with a high energy (20 kv) electron beam focused to a diameter of a few microns. Three different detectors of the SEM/EDS will be used to study minerals in thin sections. Additional concepts that may be introduced in this lab include: formula calculations, solid solution, exsolution, and chemical zoning.

Higher order thinking skills goals for this activity

  • Data analysis

Other skills goals for this activity

  • Operating analytical equipment
  • Improving writing skills to describe data

Description of the activity/assignment

This lab is designed as an introduction to the investigation of minerals with the Scanning Electron Microscope (SEM) and the X-ray analyzer (Energy Dispersive Spectrometer - EDS). We will explore the relationships among the optical image, the backscattered electron image, and the chemical composition of minerals in thin-sections that we have studied optically. Specifically we will examine the interaction of a mineral with a high energy (20 kv) electron beam focused to a diameter of a few microns. Three different detectors of the SEM/EDS will be used to study minerals in thin sections. Additional concepts that may be introduced in this lab include: formula calculations, solid solution, exsolution, and chemical zoning.

Determining whether students have met the goals

Students have met the goals of this activity if they perform the assigned tasks and correctly answer the embedded questions.

More information about assessment tools and techniques.

Teaching materials and tips

Other Materials

Supporting references/URLs

Brady, J., Mogk, D. W., and Perkins, D., (editors), 1997, Teaching Mineralogy, a workbook published by the Mineralogical Society of America, 406 pp.

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