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
Diane

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

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
Diane

4. Dichotomous Key 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
Jen

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
Diane

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

7. Mineral Storage
Jen

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
Diane

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.
Jen

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
Diane

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:
Jen

12. Does the mineral have metallic luster?
Yes
Jen 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?No

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

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

18. Yes – Calcite!

19. No - Halite
Try Again!

20. Does the rock have minerals you can see without magnification?
Yes
Rock 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?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!