GeoClick: reading the Michel Levy Color chart

This page is authored by Katharine Johanesen, Juniata College.

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Initial Publication Date: July 19, 2021

Summary

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.

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Learning Goals

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

Prompts:

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.


Prediction/Process: 

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.