ContextAudience: mid-level mineralogy course.
Skills and concepts that students must have mastered: This activity assumes students are familiar with the olivine crystal structure and are familiar with the concept of order/disorder within crystals. Students should also 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, solid solutions, or nesosilicate mineral structures.
GoalsContent/concepts goals for this activity: Students who complete this exercise should be able to:
- Use the American Mineralogist Crystal Structure Database to obtain crystal structures of synthetic olivines.
- Use a crystallographic visualization program (such as CrystalMaker or XtalDraw) to identify which elements are housed in which crystallographic sites in the olivine structure.
- 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: This exercise requires students to apply the abstract concept of crystallographic order to a dataset in which the amount of order within two cation sites is temperature-dependent. Students are also asked to think about the relationship between crystallographic order and entropy.
Other skills/goals for this activity: Students gain practice in (1) using crystallographic software to solve geologic problems, (2) using an Excel program to plot data, and (3) writing answers to open-ended questions.