Unformatted text preview: (2) Imagine you are constructing a thin section and you find a quartz grain cut parallel to the c axis that shows an interference color of first order reddish ( ∆ ~430nm). What is the thickness of this thin section? You continue to grind the thin section for another half hour and look again. The grain now has an interference color of light gray ( ∆ ~240nm). What is the thickness now? Are you happy about the quality of your thin section? Why? (3) Draw a uniaxial indicatrix: a) indicate on the drawing the location of the principal section, the circular section and one random section; b) draw these three sections next to the drawing of the indicatrix and label the ε , ε ’, and ϖ vibration directions; c) indicate if your indicatrix is for an optically positive or negative mineral? (4) Briefly describe the angular relationship between the crystallographic axes and the indicatrix axes for both uniaxial and biaxial minerals. 1...
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- Spring '11
- refractive index, Interference color, highest interference color