Crystal Measurement and Axial Ratio Laboratory

George R. McCormick
,
University of Iowa
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Summary

This exercise is designed to help students understand relationships among external morphology of crystals (their shape and faces), internal structure (unit cell shape, edge measurements, and volume), Hermann-Mauguin notation for the 32 crystal classes, and Miller Indices of forms and faces.

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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

Students should know basic geometry (e.g. measuring angles) and crystallography.

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

This exercise is designed to help students understand relationships among external morphology of crystals (their shape and faces), internal structure (unit cell shape, edge measurements, and volume), Hermann-Mauguin notation for the 32 crystal classes, and Miller Indices of forms and faces by having students measure angles in crystal structures.

Higher order thinking skills goals for this activity

This activity helps students use models to understand crystal structures.

Other skills goals for this activity

Description of the activity/assignment

This exercise is designed to help students understand relationships among external morphology of crystals (their shape and faces), internal structure (unit cell shape, edge measurements, and volume), Hermann-Mauguin notation for the 32 crystal classes, and Miller Indices of forms and faces.


The example and four crystal measurement problems have been drawn using the computer program SHAPE (see both Brock and Velbel, this volume). Both a single drawing and stereo pair are given for each problem. The stereo pair drawings can be used with the normal stereoscope used to read air photographs. The interfacial angles were calculated by the SHAPE program. If you have access to SHAPE you can design other crystal problems or have students generate the crystal drawing on the computer and then make the calculations ask for in this exercise.

Determining whether students have met the goals

Students have met the goals of this activity if they correctly and thoroughly answer the questions embedded in the laboratory activity handout.

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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