Mineral Identification Using a Student-Friendly Dichotomous Key

1. Mineral Identification Using a Student-Friendly Dichotomous Key Diane A. McCallum & Jennifer M. Allison Chambersburg Area School District Chambersburg, Pennsylvania NSTA National Conference on Science Education Philadelphia, Pennsylvania March 21, 2010

2. Standards • National Science Education Standard • A: Science as inquiry – abilities necessary to do scientific inquiry. • D: Earth science – structure of the Earth system • Pennsylvania Standard • 3.3.10.A1 – Describe the rock cycle and the processes that are responsible for the formation of igneous, sedimentary, and metamorphic rocks

3. Traditional Mineral Identification Labs • Take several days to complete • Often lead to student frustration • Without careful monitoring, students may make mistakes in tests, thus making errors in identification

4. Advantages Requires less class time Key has built-in checks More inquiry based Disadvantages Students do not identify a large number of samples Some samples can be identified through process of elimination Dichotomous Key

5. Why use a dichotomous key? • Students identify a few, carefully selected minerals • Checks are built in to correct errors • Takes less time • Students can progress at their own pace, in any order they choose

6. How much teacher prep time is required? • Determine which minerals to use ~10 minutes • Determine how minerals will be stored ~10 minutes • Prepare dichotomous key ~30-60 minutes • Assign groups ~15 minutes

7. Mineral Storage

8. Materials • Mineral and/or Rock dichotomous key(s) • Lab instructions • Mineral sets and/or Rock sets • Weak hydrochloric acid • Streak plate • Glass • Magnifying lens • Pencil

9. Procedure • Students pick up materials. • One mineral is identified as a class. • Students work with lab groups to continue identifying the remaining mineral samples. • Clean up approximately 5 minutes before the class ends. • Work with group to complete follow-up questions.

10. How much class time is required for lab completion? • At the 8th grade level, class periods are approximately 40 minutes long. • Advanced – 1 to 2 days per lab • General Level – 2 to 3 days per lab

11. Suggestions • Check your samples before creating a dichotomous key • The following minerals are good to do together: galena, magnetite, chalcopyrite • Conglomerate & breccia can be difficult, depending on your samples:

12. Does the mineral have metallic luster? Yes No

13. Yes – Does the mineral have gray or silver streak? Try Again!

14. No – Is the mineral white or clear? Yes No

15. Yes – Does the mineral show cleavage? Yes No

16. No – Does the mineral scratch glass? Try Again!

17. Yes – Does the mineral react with acid? Yes No

18. Yes – Calcite!

19. No - Halite Try Again!

20. Does the rock have minerals you can see without magnification? Yes No

21. Yes – Is the rock multi-colored? Try Again!

22. No – Does the rock have minerals you can see with magnification? Yes No

23. Yes – Is the rock a dark color? Try Again!

24. No – Is the rock shiny like glass? Yes No

25. Yes - Obsidian Try Again!

26. No – Does the rock have air holes? Yes No

27. Yes – Is the rock dark in color? Yes No

28. No Try Again!

29. Yes - Scoria Try Again!

30. No – Does the rock float in water? Yes No

31. Yes - Pumice

32. No Try Again!