Petrology Final Review

Order of interference colors is based on...

• Fluorescence of the mineral

• Difference in refractive index in different directions through the mineral

• Density

• Color of the mineral in hand sample

What do you call a mineral that is always extinct in XPL?

• Opaque

• Black

• Isotropic

• Anisotropic

Pleochroism describes the variation of color of a mineral while rotating in...

• XPL

• PPL

What is the optic sign of this interference figure?

• Uniaxial (+)

• Uniaxial (-)

• Biaxial (+)

• Biaxial (-)

Answer explanation

Remember, for uniaxial: BURP (Blue Upper Right Positive!)

What kind of cleavage does olivine have?

• 2 planes 90º

• 1 plane

• 2 planes 60º/120º

• None

Answer explanation

Olivine typically has arcuate fractures!

This quartz exhibits __________ extinction.

Which mica (or mica-like mineral) is this? (XPL)

• Lepidolite

• Chlorite

• Muscovite

• Biotite

Identify this brown, high-relief, wedge-shaped mineral. (PPL)

• Apatite

• Zircon

• Biotite

• Titanite (sphene)

What do you call a mineral that is black in both XPL and PPL?

• Black

• Isotropic

• Opaque

• Anisotropic

Identify this metamorphic mineral. (XPL)

• Kyanite

• Hornblende

• Titanite (sphene)

• Staurolite