Optical minerology - Book by Kerr Flashcards
What does snells law relate to?
Refraction
What is refraction?
when light passes obliquely from one medium to another the velocity changes and undergoes abrupt direction change
What is another name for double refraction?
Birefringence
What are the first order birefringence colours?
Blue-gray
White
Pale-yellow
Orange
Red
What are the second order birefringence colours?
Violet-blue
Blue-green
Green
Yellow
Red
What are the third order birefringence colours?
Blue-green
Green
Yellow
Orange
Red
(will be paler then that of lower orders)
What are the fourth order birefringence colours?
Pink
Pale-green
Pale-green
Pale-orange
Pale-Orange
What feature within a mineral under microscope can be used to show inclination of extinction?
cleavage
What are the types of extinction?
Parallel
Symmetrical
Inclined
What is parallel extinction?
if the cleavage in the mineral is parallel to vibration direction
What is inclined/ oblique extinction?
when the 2 cleavages cross with an oblique angle to plane of vibration
What do you call extinction when a mineral doesn’t have cleavage?
indiscriminate
What is symmetrical extinction?
when the mineral becomes dark when parallel to diagonals of rhombic pattern
What will anisotropic minerals exhibit in varying degrees as rotated?
a change in colour called pleochroism
How can cleavage be described?
ever present ability of mineral to separate into smaller and smaller particles bound by smooth surfaces
