Mineral Identification Using a StudentFriendly Dichotomous Key Diane

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

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. A 1 – Describe the rock cycle and the processes that are responsible for the formation of igneous, sedimentary, and metamorphic rocks

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

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

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

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

Mineral Storage

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

Procedure 1. Students pick up materials. 2. One mineral is identified as a class. 3. Students work with lab groups to continue identifying the remaining mineral samples. 4. Clean up approximately 5 minutes before the class ends. 5. Work with group to complete follow-up questions.

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

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:

Does the mineral have metallic luster? Yes No

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

No – Is the mineral white or clear? Yes No

Yes – Does the mineral show cleavage? Yes No

No – Does the mineral scratch glass? Try Again!

Yes – Does the mineral react with acid? Yes No

Yes – Calcite!

No - Halite Try Again!

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

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

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

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

No – Is the rock shiny like glass? Yes No

Yes - Obsidian Try Again!

No – Does the rock have air holes? Yes No

Yes – Is the rock dark in color? Yes No

No Try Again!

Yes - Scoria Try Again!

No – Does the rock float in water? Yes No

Yes - Pumice

No Try Again!