ORE DEP (ORE MICROSCOPY)

Question 1

Thin section: Petrography = _________: Ore Micrsocopy

Answer 1

Polished Sections

Question 2

Difference of Ore Microscope vs Petrographic Microscope?

Answer 2

Ore Microscope uses Incident Light which allows examination of PLOSHED SURFACES of OPAQUE MINERALS under REFLECTED LIGHT

Light source above the thin section

Petrographic: Transmitted Light
Light source below the section

Question 3

The distance between the specimen and the objectives

Answer 3

Free working Distance

Question 4

Types of Objectives

Answer 4

1) Achromat - corrected for spherical aberration of 1 color (Yl.Grn) and for Chromatic Abberation for two colors
2) Apochromat - corrected for spherical aberrationof 2 colors (blue green) and Chromatic Abberation for primary colors
3) Flourite - Between

Question 5

The degree by which the image is enlarges as light passes through the objective

Answer 5

Magnification of an object

Question 6

Measure of the ability to distinguish fine structureal details in a specimen and determines the depth of focus and the useful range of magnification

Answer 6

Numerical Aperture (NA)

Question 7

Most commonly used low-to medium- magnification objetives fo ore microscopic work and is designed to have only air in between the ibjective and the sample

Answer 7

Dry/Air Lenses

Question 8

Thickness of the cover glass in Thin Sections

Answer 8

0.17-0.18 mm

Question 9

Commonly used objectives for reflected light microscopy especially when high magnification and high resln is required

Answer 9

Immersion objectives

Question 10

Immersion Oil Index of refraction

Answer 10

n=1.515

Question 11

The higher the objective power

Answer 11

The higher the FWD, the larger tha angular apertures

Question 12

Difference of Oculars in Petrog in ore microscopy

Answer 12

Do not have crosshairs!!

Question 13

color of filter to produce daylight illumniation

Answer 13

Pale Blue

Question 14

Field Diapgrahm vs Aperture Diapgrahm

Answer 14

Aperture D. - reduce stray scattered liht
Field D. - controls the angle of cone of light incident

Question 15

Most Critical Component of a Ore Microscope

Answer 15

Reflector

Question 16

Types of Reflectors

Answer 16

1) 45 plane glass reflector - some is reflected some light lost
2) Smith Reflector - light enters at an angle of 22.5 deg and isotropic samples appears uniformly black in XPL
3) Totally relecting Prism - light is reflected downward through 0.5 aperture of the objective and is reflected back upward through the other half

Question 17

Used to control or provide a specified wavelength

Answer 17

Monochromators

Question 18

Used to measure Reflectance

Answer 18

Photometers

Question 19

Used to measure grain size

Answer 19

Stage Micrometers

Question 20

Process in which chemical solutions are used to enhance structures within grains subected for mineral identification

Answer 20

Chemical Etching

Question 21

Commong Ecthants

Answer 21

HNO3 -Nitric Acid
Ammonium Dichromate - HCl Soln
H2SO4 - Sulfuric Acid

Question 22

Advance Technique in Ore Microscopy

Answer 22

EPMA
Fluid Inclusion
SEM
Stable Isotope Study
XRD

Question 23

Set-up for Observing Color in Reflected Light

Answer 23

?Illuminator Field Diapgrahm and Illimunator Apertur Diapgrahm opened wide
?Low Power Objective
?High Voltage for light of good intensity
?Polarizer in, Analyzer out

Question 24

The amount of light reflected back

Answer 24

Reflectance

Question 25

Reflectance formula (R%)

Answer 25

(Intensity of Reflected Light / Intensity of Incident Light ) x 100%

Question 26

Factors which can affect amount of light reflected back to the observer

Answer 26

?Cyrstallographic Orientation of the Polished Surface relative to the vibration directions of linearly polarized incident light ?Wavelength of light ?Angle of Incidence ?Defree of Polish

Question 27

Change of Reflectance

Answer 27

Bireflectance (Anisotopism)

Question 28

Change of color or tint

Answer 28

Reflection Pleochroism

Question 29

Reflections within semi-translucent to transparent minerlas

Answer 29

Internal Reflection

Question 30

Minerals which does not exhibit Bireflectance and Reflection Pleochroism (Parang Birefringence and Pleochroism sa Petrg)

Answer 30

Isotropic Minerals (Cubic Minerals) Basal Sections of Hexaonal and Tetragonal Cyrstals

Question 31

Bireflectance is the measure of

Answer 31

The difference between the maximum and minimum values of reflectance percentage

Question 32

The resistance of particular mineral to abrasion during polishing process

Answer 32

Polishing Hardness

Question 33

The property in which hard minerals may stand slightly above the surfaces of softer grains in the section

Answer 33

Polishing Relief (Relief is a function of Hardness)

Question 34

The relative amount of surface scratchin an the depth of scratches that cross grain

Answer 34

Scratch Hardness

Question 35

Line test that is used in Reflected Ore microscopy which makes use of scratches

Answer 35

Kalb Line Test

Question 36

Mohs Scale of Hardness for ore minreals

Answer 36

Argentite 2-2.5 Galena 2.5 Chalcopyrite 3.5-4 tetraherite 3-4.5 Niccolite 5-5.5 Magnetite 6 Ilmenite 5.5-6

Question 37

Seen in polished sections as one or more sets of parallel cracks

Answer 37

Cleavage

Question 38

How are three cleavage direction seen under reflected light especially seen in Galena, Magnetite and Pentlandite?

Answer 38

Parallel rows of triangular pits

Question 39

Three types of twinnig obersved in Ore Microscopy

Answer 39

1) Growth 2) Inversion 3) Deformation

Question 40

What may be the caused of Zonal Sturctures in ore minerals

Answer 40

1) Depositional Pause during Growth 2) Different Growth Rates w/ or w/o inclusions 3) Chemcial Variations during growth

Question 41

Strong Bireflectance

Answer 41

Graphite Molyb Covellite Stibnite Vallerite

Question 42

Moderated

Answer 42

Marcasite hematite Niccolite Cubanite Pyrrhotite

Question 43

Weak

Answer 43

Ilmenite Arsenopyrite