Identifying Minerals with Chemical and Crystallographic Data

Kent Ratajeski

Montana State University

This activity is part of the On the Cutting Edge Peer Reviewed Teaching Activities collection. (view details)

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Initial Publication Date: August 7, 2006 | Reviewed: October 21, 2012 (see revision history: 4 events)

Summary

In this exercise, crystal structure data for a variety of unknown minerals are downloaded and entered into XtalDraw or CrystalMaker visualization software program. Step-by-step tutorials are provided with instructions and examples of how to use this software. Through a series of directed questions for each unknown, students investigate and manipulate the crystal structure to gather information about its possible identity.

Crystallography, Crystal Chemistry, Physical Properties, Sulfates, ...(more) | College Lower (13-14), College Upper (15-16)

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Context

Audience

mid-level mineralogy course

Skills and concepts that students must have mastered

This exercise covers a wide variety of mineral structures, building on concepts such as crystal system, coordination number, valence state, crystal chemistry, polymorphism, silica polymerization, silicate mineral classes, and non-silicate minerals.

How the activity is situated in the course

This assignment could be used towards the end of the semester, perhaps as a final homework assignment or a self-paced review exercise that the students could work through to prepare for a final exam. Alternatively, the exercise could be split up and assigned over the course of the semester as weekly extra-credit assignments or quizzes.

Goals

Content/concepts goals for this activity

understanding mineral classification, coordination polyhedra, element occupancies in various crystallographic sites, crystallographic systems, and symmetry operations within crystal structures

Higher order thinking skills goals for this activity

This exercise requires students to apply the abstract concepts of symmetry and coordination to actual crystal structures. Spatial thinking skills are also used to visualize the three-dimensionality of the crystal models with the computer (3-D glasses can be used with CrystalMaker to facilitate spatial learning).

Other skills goals for this activity

using visualization software for displaying crystal structure files

Description of the activity/assignment

In this exercise, crystal structure data for a variety of unknown minerals are downloaded and entered into a visualization program (either XtalDraw or CrystalMaker). Through a series of directed questions for each unknown, students investigate and manipulate the crystal structure to gather information about its possible identity. This exercise builds on a wide variety of content normally covered over an entire introductory mineralogy course, and could be used as a self-study exercise to help mineralogy students prepare for a comprehensive final exam.

Determining whether students have met the goals

The exercise is formatted as a self-paced exercise where students can check their own answers by clicking on "Show answer" tabs. The exercise could be reformatted as a normal homework assignment without the answers given and graded by the instructor based on his/her own evaluation scheme. If used as an evaluative instrument, outcomes could be any of the following:
written short answers to the questions, longer integrative writing assignments, or verbal articulation of answers to peers or instructors.

More information about assessment tools and techniques.