Olivine Crystal Structure
Skills and concepts that students must have mastered
- students should be familiar with the olivine crystal structure
- students should be familiar with the concept of order/disorder within crystals
- students should know how to use Excel to make x-y graphs
How the activity is situated in the course
- this activity could supplement class lectures on order/disorder
- this activity could supplement class lectures on solid solutions
- this activity could supplement class lectures on solid solutions nesosilicate mineral structures
Content/concepts goals for this activity
- students should be able to use the American Mineralogist Crystal Structure Database to obtain crystal structures of synthetic olivines
- students should be able to use a crystallographic visualization program (such as CrystalMaker or Xtaldraw) to identify which elements are housed in which crystallographic sites in the olivine structure
- students should be able to use downloaded olivine compositions and Excel to determine the ordering of M1 and M2 cations within olivine
Higher order thinking skills goals for this activity
- application of the abstract concept of crystallographic order to a dataset in which the amount of order within two cation sites is temperature-dependent
- recognition of the relationship between crystallographic order and entropy
Other skills goals for this activity
- using crystallographic software to solve geologic problems
- using an Excel program to plot data
- writing answers to open-ended questions
Description of the activity/assignment
While this study reports cutting-edge materials research carried out with the latest crystallographic techniques, the results are educationally instructive and illustrate important concepts normally covered in an undergraduate mineralogy course.
- In this exercise, students are guided into the American Mineralogist Crystal Structure Database to retrieve and download published crystal structure data for viewing in either the CrystalMaker or XtalDraw visualization software packages.
- The students are instructed on how to manipulate the structures and are asked to plot some of the crystallographic data from this study on graphs using a spreadsheet program such as Excel.
Determining whether students have met the goals
- This activity 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.
Download teaching materials and tips
- The complete activity is available from: Order/Disorder Within Crystal Structures as a Function of Temperature. This site has step-by-step tutorials that demonstrate how to access the Mineralogical Society of America Crystal Structure Database and how to use these data in the XtalDraw and CrystalMaker software packages.