Midterm Flashcards
What is a crystal?
A piece of mineral bounded by regular crystal faces formed during crystal growth.
What defines crystalline?
the ordered arrangement of atoms, ions or molecules in a crystalline material.
What are minerals?
Naturally occurring
Inorganic
Solid crystalline substances with definite chemical composition and orderly internal atomic arrangements
What are polymorphs?
Minerals with the same chemical composition but variation in crystal lattice structure
What does isotropic mean? Name an isotropic mineral
Uniform light velocity in all directions (independent of direction)
What does anisotropic mean? Name an anisotropic mineral
Light velocity depending on direction
What happens to light when it enters a mineral?
Slows down relative to air (wavelength decreases. Causes refracion
What causes the lens affect
Snell’s law (index 1/index2)
How do the filters work?
Long chains of hydrocarbons filter directionally
What do you see in a microscope w no slide and both filters?
Nothing (90 degree blocks all light)
What kind of light enters a mineral?
PPL
What is relief?
How much a mineral stands out from the mounting medium. Can be + or -
How do you tell relief magnitude?
High has thick borders, and low has small
What’s the Becke line test?
When lowering stage, White into mineral = Nmin>Noil (+ve relief) and opposite is opposite
Which is fast ray, which is slow ray?
Fast ray has lower index of refraction
