Optical Mineralogy

Question 1

Study of the interaction of light with minerals

Answer 1

Optical Mineralogy

Question 2

Opaque minerals commonly studied in reflected light

Answer 2

ore microscopy

Question 3

general application of optical mineralogy is?

Answer 3

to aid in the identification of minerals, either in rock thin sections or individual mineral grains

Question 4

It has Low power objective (10x) and Bertrand lens is optional

Answer 4

Orthoscopic (Uncrossed)

Question 5

Properties that can be observed in Orthoscopic

Answer 5

[] Color and Pleochroism
 Cleavage
 Shape and Form
 Relief/ Refractive Index (R.I.

Question 6

observed w/ plane prolonged light; not always the same as megacopic color

Answer 6

Color

Question 7

change in color of a mineral in varying degrees as
the stage is rotated due to differences in light absorption &
extraordinary rays generally expressed as a formula

Answer 7

Pleochroism

Question 8

The ability of a mineral to separate into smaller
particles bounded of faces of possible crystal form.

Answer 8

Cleavage

Question 9

qualities of cleavage

Answer 9

[] Perfect
 Good
 Poor
 None

Question 10

Directions of Cleavage

Answer 10

One Direction
Two Directions
Three Directions
Four Directions
Six Directions
All Directions

Question 11

-can be expressed by using the terms
eubedral subhedral anhedra

Answer 11

Shape and Form

Question 12

no recognizable crystal form

Answer 12

anhedral

Question 13

show imperfect but recognizable
crystal form

Answer 13

subhedral

Question 14

show sharp and clear crystal form

Answer 14

euhedral

Question 15

degree of visibility of a transparent mineral in an immersion medium

Answer 15

Relief

Question 16

R.I of Canada balsam

Answer 16

1.53

Question 17

index of refraction (R.I) of the mineral is Higher than the medium

Answer 17

. HIGH RELEF

Question 18

-R.I of the mineral is lower than the medium

Answer 18

LOW RELIEF

Question 19

almost the same with the medium

Answer 19

ZERO RELIEF

Question 20

varies as the stage is rotated, takes place if one n
mineral is near n balsam, and the other n mineral

Answer 20

CHANGE of RELIEF

Question 21

the contrast between a mineral and its
surroundings due to difference in refractive index.

Answer 21

Relief

Question 22

Relief is __________ when the grain has higher refractive index than surroundings

Answer 22

positive

Question 23

Relief is __________ when the grain has lower refractive index than surroundings

Answer 23

negative

Question 24

ratio of the velocity of light in a vacuum to its
velocity in the medium

Answer 24

Refractive Index

Question 25

R.I, constant velocity in all directions

Answer 25

isotropic/ isotropic substances

Question 26

more than one R.I, light velocities vary with direction

Answer 26

anisotropic

Question 27

a band or rim of light visible along a grain/crystal boundary in plane-polarized light.

Answer 27

Becke line

Question 28

It is best seen using the intermediate power lens (or low
power in some cases), on the edge of the grain, with
the diaphragm stopped down a bit

Answer 28

Becke line

Question 29

Those with uniform physical properties in all direction

Answer 29

Isotropism