GeoClick: reading the Michel Levy Color chart
A practice and review exercise that asks students to use the Michel-Levy Color chart to find observed interference colors, determine birefringence, and predict changes in interference color based on thickness of the mineral.
Students should be familiar with using the chart and
Students should be able to apply the chart to determine birefringence
Students should understand how thickness and birefringence produce specific interference colors.
Context for Use
Appropriate for Mineralogy or Petrology undergraduate students, after they have learned about birefringence, interference colors, and have been introduces to the Michel-Levy chart
Description and Teaching Materials
Scaffolding / Orientation:
1. Click on the chart where the band of color for 2nd order red intersects with a 30 micron thickness.
2. If you have a standard 30 micron thick thin section and your mineral shows 2nd order red colors (from question 1), click where you would read the birefringence for that color and thickness.
3. If a mineral of standard thickness (30 microns) has 2nd order red interference colors (box in red), what interference colors would you expect when it is ground down to 20 microns thick?
Teaching Notes and Tips
I suggest having students discuss their answers between each question.