LAB

Question 1

RI formula

Answer 1

R.I.= Vvacuum/ Vmineral

Question 2

Relief

Answer 2

Is the difference between the RI of the medium with the mineral

Question 3

Steps to find the Becke line

Answer 3

1- Use plain polarized light
2-focus at a grain boundary
3- Set the substage iris diaphragm in nearly closed
4- Increase the distance between the stage and the objective lens by slightly turning the fine focus towards you
5- what the Becke line move in or out

Question 4

In how many step can we determine relief?

Answer 4

2 steps:

1- High, moderate and low

2- Positive or negative

Question 5

If the becke line moves in, the mineral has a…..and if moves out of the grain, it has……. Relief.

Answer 5

Positive……..Negative

Question 6

How many times does a pleochroic mineral changes color during a full stage rotation?

Answer 6

2X

Question 7

In what line you check for pleochroism??

Answer 7

Plain polarized light

Question 8

In cross polars, the mineral gets extinct……….in a full stage rotation.

Answer 8

4X

Question 9

Isotropic

Answer 9

Transmit light with the same velocity regardless of direction. Only one refractive index

Question 10

Anisotropic

Answer 10

(uniaxial and biaxial): light entering an anisotropic crystal in all but 1 or 2 special directions (optic axis) is resolved into two plane polarized components perpendicular to each other. 1 fast and 1 slow

Question 11

What test can be done to differentiate isotropic to anisotropic minerals?

Answer 11

Test of interference figures

Question 12

The greater the velocity that lights travel, the………. Is the R.I.

Answer 12

Lower

Question 13

What is garnet system form?

Answer 13

Cubic

Question 14

What is crystal form of isotropic minerals?

Answer 14

Cubic

Question 15

What test you can do if a mineral appears isotropic?

Answer 15

Do an interference figure

Question 16

What are the vibration direction in calcite?

Answer 16

E and O

Question 17

What are the refractive indices for calcite?

Answer 17

Epsilon and Omega

Question 18

What is birefringence?

Answer 18

Is the measure of double refraction in terms of the difference in refractive indices

B=|n (max) - n (min)|

Question 19

What kind of light do you need to see relief?

Answer 19

Plain polarized light

Question 20

How to measures refractive index?

Answer 20

May be measured by comparison between the substance of known RI (mounting medium of Canada balsam that has RI = 1.54, or oils or epoxy of known RI, or a mineral of known RI in physical contact with the mineral of interest.