Optical Mineralogy Lab 1 of 2: PPL

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Optical MineralogyLab 1 of 2 PPL

• Plain polarized light

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Pleochroism
Color changes as the stage is rotated
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Pleochroism

• In some slides the range of colors will be seen
  right away (blue to purple here)
• Why??

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Relief?

• Low
• Note how each blend to the other minerals

• High
• Sharp boundaries and cleavage lines

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Cleavage

• Easier to pick out in thin section than hand
  sample
• What is the cleavage angle here

120º /60º
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Cleavage?

• Rhombohedral

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Cleavage?
90º
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Crystal Shape

• This was in last weeks pre-lab lecture
• What are they?????

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Types of crystals

• Euhedral
• Subhedral
• Anhedral
• Amorphous

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Slides for today Garnet
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Corundum
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Hornblende
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Kaersutite
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Glaucophane
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Aegirine
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Chlorite