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Mineralogy (4 credit hours)
SGES 1272/74
Tuesday 2-3 (T), 3-5 (P)
Thursday 2- 4 (P)
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Prof Emeritus C.S. Hutchison
Dr. Nur Iskandar Taib Mr. Mohd Azamie
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Learning Outcomes
At the end of the course, the student should be able to:
1. Able to use a petrology microscope.
2. Demonstrate use of the theory beside opticalproperties used to identify minerals.
3. Identify most of the rock forming minerals using apetrology microscope, both in isolation and in rocks.
4. use standard mineralogical reference texts.5. Demonstrate use of the concepts within mineralogy,
such as crystallography, solid solution and exsolution.
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Synopsis of Course Contents
The first part of the course introduces the petrographicmicroscope,and the optical properties that are usedwhen identifying minerals.
The second part of the course introduces some of theconcepts used in crystallography, and some of thechemistry behind mineralogy.
Concurrently with this, the student is also introducedto the rock forming minerals in a systematic way, andlearns to identify them using the petrographicmicroscope and standard reference texts.
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Method of Delivery : Lecture and Practical with
notesAssessment Methods : Tests and Examination
References :
Deer, W.A., Howie, R.A. & Zussman J.,
1971. An Introduction to the Rock FormingMinerals. Longman, London.
Kerr, F.K.,1959. Optical Mineralogy. McGraw-Hill. New York.
Moorhouse, W.W., 1959. The Study ofRock in Thin Section. Harper Row Publication
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Mineralogy ?
Optical mineralogy - the study of the
interaction of light with minerals, most
commonly limited to visible light and usually
further limited to the non-opaque minerals.
Opaque minerals are more commonly studied
in reflected light and that study is generally
called ore microscopy - alluding to the fact
many opaque minerals are also ore minerals.
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Polarizing Microscope /
Petrographic Microscope
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thin sections
What are thin sections? Thin sections are made from small slabs of a rock sample
glued to a glass slide (~1 inch by 2 inches), and then ground to a specified
thickness of 0.03mm (30 microns). At this thickness most minerals become moreor less transparent and can then be studied by a microscope using transmitted
light. Thin sections are time consuming and costly to prepare.
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The nature of polarised light
Light travels as electro-magnetic vibrations in
which the vibration direction is transverse to
the direction of propagation. Transverse wave-
motions of this type are said to be plane
polarised when all the vibrations lie in one
plane. Light from the sun is unpolarised but
when it reflects off a surface it becomes partlypolarised as shown opposite.
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polarised light
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Becke Line Method
Are defined as the broad, dark or bright lines
(due to refraction and/or diffraction) formed
in the image at the boundary between media
of different optical path lengths. They move in
the direction of the longer optical path when
the distance between the objective and the
object is increased. The Becke line disappearsin the region of the object that lies in exact
focus.
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BeckeLine Method
1.Use medium objective in PPL
2.Close down aperture diaphragm some
3.Lower stage
4.Beckeline is band of light along grain boundaries
5.IfBeckeline moves into oil from mineral, n oil > n mineral
6.IfBeckeline moves into mineral from oil, n mineral > n oil
Colored Beckelines indicate n mineral = n oil.
Orange yellow line into mineral
Green-blue line into oil
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Relief
You will immediately notice when you look at thin sections that someminerals are clearly visible (that is, details of surface texture, cleavage,etc., are obvious) while others appear almost featureless and, ifcolourless, barely visible. This is the property known as relief.
Minerals which have refractive indices which differ markedly from that of
the mounting medium (the glue used to stick the rock slice to the glassslide and the cover slip to the rock) show up clearly in thin section and aresaid to have high relief. Minerals with low reliefhave refractive indicesclose to that of the mounting medium of about 1.54.
Relief is a useful distinguishing property for the the igneous rock-fromingminerals; all the mafic minerals show high relief but all the felsic minerals(with the exception of muscovite) show low relief.
This thi section shows examples of contrasting relief. The high reliefmineral is clinopyroxene and the low relief mineral is plagioclase feldspar.
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