OM and Petrography Flashcards
Used extensively to examine transparent minerals, fragments, grains and small crystals, as well as thin sections of minerals, rocks and other crystalline aggregates
Polarizing Microscope
cut to such thickness that it increases or decreases retardation of a section by about 1/4λ
Mica Plate
It is used to determine fast and slow directions (electric vectors) of light polarization in crystals under view on the microscope stage by increasing or decreasing retardation of the light
Gypsum Plate
beam of light consists of a stream of minute particles, or photons, given off at high velocity by a luminous body that travel through space in straight lines and eventually reach the eye.
Corpuscular Theory
useful in the determination of the optical properties of individual crystals or aggregates and in the interpretations of textures, structures, growth patterns, and various relationship of natural or artificial substance.
Polarizing Microscope
considered light to be transmitted by the vibration of particle in the waves. The phenomena of light such as reflection, refraction, diffraction and interference may be readily explained in accordance with this theory.
Wave Theory
ground to produce interference colors from the beginning of the first to the end of the third or fourth order. Equals 0.009
Quartz Wedge
He is the proponent for the Wave Theory
Christian Huygens
considered light as made up of waves but said that waves are electromagnetic. A wave consists of rapidly alternating electric and magnetic fields normal to each other and normal to the direction of propagation of light
Electromagnetic Theory
He is the proponent for the Electromagnetic Theory
James Clerk Maxwell
assuming that radiating oscillators in a black body radiate energy discontinuously in units
Quantum Theory
black body that radiate energy discontinuously in units are called
Quanta
defined as the locus of all the points of a medium, which receives light wave disturbance simultaneously so that all these points are, in the same phase
Wave Front
a perpendicular drawn to the surface of a wave front at any point in the direction of propagation of light
Wave Normal
The direction in which light is propagated
Ray of Light
the wave normal and the direction of propagation of the light rays are perpendicular to the wave front
Isotropic
may represent a curve combining movement around a circle with motion along a straight line
Displacement
lies in the wavefront and is perpendicular to the ray in isotropic media. In anisotropic media, it is only perpendicular in limited directions
Vibration Direction
The light rays are not parallel to the wave normal
Anisotropic
distance between two successive crests or troughs, or any corresponding distance along the wave.
Wavelength
surface determined at a given instant by all parts of a system of waves traveling along the same direction and in the same phase. In anisotropic, it is perpendicular only in certain directions.
Wavefront
direction perpendicular to the wavefront. In isotropic, the wave normal and ray direction are the same. In anisotropic, they differ aside from certain directions
Wave Normal
number of vibrations in a given unit of time
Frequency
maximum displacement of a wave from the line of transmission
Amplitude
time interval necessary for a wave to undergo a complete oscillation
Period
point of the wave with the maximum upward displacement
Crest
point of the wave with the greatest downward displacement
Trough
a group of light waves following along a sample path
Beam
straight-line path followed by light in moving from one point to another
Ray
equal to the ratio of the wave-normal velocity in a vacuum to the wave-normal velocity in the medium whether isotropic or anisotrophic
Refractive Index
light of a single wavelength
Monochromatic Light
lies parallel to the plane of the wavefront. In isotropic, perpendicular to the direction of the propagation. In anisotropic, still parallel but not perpendicular to the direction of the propagation
Light Vector
measures the electrical displacement
Electric
measures the magnetic displacement or induction
magnetic
combination of all the different wavelengths visible to the eye. Maybe considered composed of seven different colors
White light
speed of light
186,284 mi/s
realistic virtual image with a flat field
Orthoscopic Observation
Low to high magnification objective
Analyzer out
Condenser top lens out
Bertrand lens out
PPL or Plane Polarized Light or Uncrossed Nichols
What solution is used to clean the thin section?
Xylol Solution
High magnification objective (40x) Analyzer in Condenser top lens in Bertrand lens in Accessories in
Conoscopic Observation
Study of the interaction of light with minerals
Optical Mineralogy
Low to high magnification objective
Analyzer in
Condenser top lens out
Bertrand lens out
XPL or Cross Polarized Light or Crossed Nichols
yields interference figures which represent an optical pattern caused by the behavior of light in individual crystal
Conoscopic Observation
Study of opaque minerals commonly studied in reflected light
Ore Microscopy
observed w/ plane prolonged light; not always the same as megacopic color
Color
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
Pleochroism
the ability of a mineral to separate into smaller particles bounded of faces of possible crystal form. Expressed or best explained in terms of direction
Cleavage
can be expressed by using the terms eubedral subhedral anhedral; lath-shape, bladed etc
Shape and Form
Grains that show no recognizable crystal
Anhedral
Grains that show imperfect but recognizable crystal form
Subhedral
Grains that show sharp and clear crystal form
Euhedral
degree of visibility of a transparent mineral in an immersion medium
Relief
relief of Canada balsam
1.53
index of refraction (R.I) of the mineral is Higher
than the medium
High Relief
R.I almost the same with the medium
zero relief
R.I of the mineral is lower than the medium
Low Relief
varies as the stage is rotated, takes place if one n
mineral is near n balsam, and the other n mineral
Change of Relief
the contrast between a mineral and its surroundings due to difference in refractive index.
Relief
is the ratio of the velocity of light in a vacuum to its velocity in the medium
Refractive Index
is a band or rim of light visible along a grain/crystal boundary in plane-polarized light. 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
Becke Line
is the result of two things, both related to refraction along the boundaries of mineral grains
Becke Line
Those that display colors in varying degrees as the stage is rotated
-Produces interference color
Anisotropism
- Those w/ uniform physical properties in all directions
- Remain dark in all positions even if the stage is rotated.
istropism
observed w/ reference to the Michel – Levy Chart
Interference Color
is used in describing interference colors
Order
This maximum colour is often diagnostic of an anisotropic mineral and it is observed in sections that display simultaneously the maximum and minimum refractive indices.
Birefringence
Formation of rational symmetry intergrowth of 2 or more grains of crystalline species.
Twinning
Form of penetration twinning where two crystals form as penetration twins
Carlsbad Twinning
common within the plagioclase feldspars, in places where two adjoining twin slabs or lamellae are mutually reversed with respect to each other and every alternate twin ‘plate’ or ‘slab’ has an identical atomic structure.
Lamellar Twinning
shows two kinds of repeated twinning in thin section, with one set of twins arranged at 90° to the other set. The lamellar twins overlap each other and have ‘fuzzy’ edges, giving a ‘tartan’ appearance.
Cross-Hatched Twinning
Refers to solid solution which do not have uniform composition.
Zoning
center is more sodic becoming more calcic toward the margin
Normal Zoning
normally steplike progressions for more calcic interior to more sodic margins w/ local reversals in adjacent zones
Oscillatory Zoning
center is more sodic becoming more calcic toward the margin
Reverse zoning
when a mineral becomes dark parallel to the crosshairs.
Parallel Extinction
at an angle with the direction of polars
Inclined Extinction
or
Oblique Extinction
planes of mineral to the diagonal; vibration direction is diagonal
Symmetrical Extinction
two arms of the cross form
Isogyre
Interference Color, identical to those on the color chart.
Isochrome
The point where Isogyres cross
Melatope
The identification or interpretation of framework mineralogy and textures leading to classification of wallrock as sedimentary, metamorphic or igneous.
Petrography
refers to degree of crystallinity, grain size or granularity, and the fabric or geometrical relationship between the constituents of a rock.
texture
consist wholly of crystals
Holocrystalline
Identification of replacement mineralogy and paragenesis, and interpretation in terms of histories of diagenesis, metamorphism, hydrothermal alteration and/or weathering.
Petrography
consist entirely of glass
Holohyaline
Contain both crystals and glass
Hypocrystalline
or
Merocrystalline
Extremely minute, incipient crystals, provided they are birefringent
Microlite
Smaller, spherical, rod- and hair-like isotropic from.
Crystallite
Fine grained texture
Aphanitic or Eucrystalline
Very-fine and undistinguishable under petrographic microscope
Cryptocrystalline
Coarse Grained texture
Phaneritic or Dyscrystalline
Very-coarsed grained texture
Pegmatitic
Crystals were not bounded by crystal faces.
a. met
b. sed
c. ign
a. automorphic
b. idiomorphic
c. euhedral
Crystals were partially bounded by crystal faces.
a. IGN
b. SED
c. MET
a. Anhedral
b. Allotriomorphic
c. Xenomorphic
Crystals were not bounded by crystal faces.
a. IGN
b. MET
a. Subhedral
b. Hypidiomorphic
- Chiefly minerals are anhedral.
- Common in aplites
a. IGN
b, MET
c. SED
d. Mineral
a. Aplitic
b. Xenomorphic Granular
c. Allotriomorphic Granular
d. Sugary/ Saccharoidal
- If chiefly minerals are euhedral
- Common in dark hypabyssal rock
a. MET
b. IGN
c. SED
a. Automorphic Granular
b. Lamprophyre
c. Panidiomorphic Granular
If all faces are present
a. MET
b. SED
c. IGN
Hypidiomorphic Granular
Hypautomorphic Granular
Granitic
the phenocrysts lie in a matrix of glass
Vitrophyric texture
If the groundmass is a dense intergrowth of quartz and feldspar
Felsophyric Texture
If the groundmass of feldspar are rectangular in form instead of slender lath crystals
Orthophyric Texture
term used to describe a porpyritic texture in which phenocrysts are clustered into aggregates
Glomeroporphyritic Texture
or
Glomerophyric texture
accumulation of crystals occurs by surface tension and fixing by interpenetration due to crystal growth
Synneusis
is widely used to determine order of crystallization; if one mineral is enclosed by another then the enclosed grain must have been the first to crystallize. This may sometime be true , but it is certainly not always so.
Poikilitic Texture
one where random plagioclase laths are enclosed by pyroxene or olivine.
Ophitic Texture
plagioclase is larger and encloses the ferromagnesian minerals
Sub-Ophitic Texture
Angular interstices between feldspars filled with glass instead of pyroxene
Hyalophitic Texture
A genetic term for a border of secondary minerals formed at the margin of a primary grain in an igneous or metamorphic rock
Reaction Rim or Corona Texture or Opacitic Rim
Formed from post-magmatic reaction
Reaction Rim or Corona Texture or Opacitic Rim
Secondary rim/coronas
Kelyphitic Rim
a textural term indicating that a crystal occupies the angular space between at least two larger crystals. Intergranular crystals have crystallised later than the crystals that control their shape
Intergranular Texture
A textural term used to denote that the angular spaces between larger crystals is occupied by glass, or glass and small crystals. The glass may be devitrified or altered to other phases.
intersertal texture
Texture of the groundmass of a holocrystalline igneous rock in which lath-shaped microlites (typically plagioclase) are arranged in a glass-free mesostasis and are generally interwoven in irregular unoriented fashion.
Pilotaxitic Texture
A texture of extrusive rocks in which the groundmass contains little volcanic glass and consists predominantly of minute tabular crystals, namely, sanidine microlites
Trachytic Texture
An intergrowth of branching rods of quartz set in a single crystal of plagioclase, neighboring rod of quartz have the same lattice orientation and extinguish together.
Myrmekitic Texture
Plagioclase commonly exhibits a variety of disequilibrium textures in volcanic rocks, especially in orogeny andesites
Sieve Texture
Is an intimate intergrowth of sodic and potassic feldspar resulting from subsolidus exsolution
Perthitic Texture
A process by which a solid solution phase unmixes into two separate phases in the solid state.
Exsolution
occurs only in minerals whose compositions vary between two or more pure endmember compositions.
Exsolution
is an intergrowth arising due to exsolution where potassic feldspar is present as blebs or lamellae within a sodic feldspar
Anti-Perthitic Texture
occurs in rocks that are rich in alkalies; hence the vitreous mass of the rocks has a relatively low viscosity
Trachytic Texture
