1. Look at the glaucophane slide BH250-7. The pleochroic formula for glaucophane is: X=colorless, Y=pale violet, Z=deep blue. Knowing that glaucophane is a negative mineral, what two colors would you look for if you were trying to find a grain properly oriented to give you a Bxa figure? For a Bxo? For a flash figure? And for a centered optic axis figure? Look at the slide to see if you are correct.
What is the 2V for glaucophane?

2. Look at a slide containing biotite BH-250-14 . Look up the pleochroic formula and see if you can determine the orientation of individual grains like you did in #1. (This one's just for practice)

3. Look at the slides of biotite, glaucophane, olivine, and hornblende. Look at these minerals and make a table of important characteristics. Record only things you observe.

Plechroism is demonstrated here in these pictures of....

Mineral under plane polarized light	again but now rotated 90 degrees clockwise

Mineral under plane polarized light	again but now rotated 90 degrees clockwise

The above pictures were taken from Professor Bereket Haileab's Powerpoint presentation entitled Lecture 1.

To see this lecture go to The Lectures page and click on Lecture 1.

biotite under plane polarized light	the same biotite rotated 90 degrees counter clockwise

www.gly.bris.ac.uk/www/ teach/opmin/mins.html