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MINERAL, BATUAN DAN FOSIL
ARKEOGEOLOGI
UAW302
SAINS DALAM ARKEOLOGI
SEMESTER KDUA 2010/2011
1. HUBUNGAN BATUAN, MINERAL DAN FOSIL DENGAN
MANUSIA
2. PENGENALAN KEPADA BATUAN
3. PENGENALAN KEPADA MINERAL
4. KAEDAH ANALISIS
1. Petrograpy
2. SEM
3. XRF
4. XRD
KULIAH INI AKAN DIBAHAGIKAN KEPADA:
A collection of stone age tools: Bronze Age Tools
2
� Mining, smelting, and casting became organized efforts.
Iron Age Tools
3
Geoarchaeology:
represents the application of geographical
and geological concepts and methods to
aid in the interpretation of the
archaeological record of ancient human
societies.
Geology + Archaeology KENALPASTI BATUAN, MINERAL ATAU ELEMEN
SECARA MIKROSKOPIK DAN MAKROSKOPIK
Rocks
� A rock is a hard substance composed of
one or more minerals. A rock can also
be made of or contain naturally occurring
substances that do not perfectly fit the
definition of a mineral. Rocks can be
composed of volcanic glass or of opal.
Both of these substances lack a
crystalline structure.
4
�� Lithosphere is the solid part of the Earth.Lithosphere is the solid part of the Earth.
�� Crust is the outermost solid part of the Crust is the outermost solid part of the
Earth.Earth.
�� The EarthThe Earth’’s crust is not evenly thick.s crust is not evenly thick.
5
The Formation of RocksThe Formation of Rocks
�� Principal rock types:Principal rock types:
�� IgneousIgneous 65%65%
�� MetamorphicMetamorphic 27%27%
�� SedimentarySedimentary 8%8%
The Rock CycleThe Rock Cycle
6
Igneous Rocks
� Igneous rocks were originally hot, fluid
magma within the Earth. Igneous get
their name from the Latin word, ignis,
which means “fire”.
Igneous Rocks
� Igneous rocks are classified according to their composition and texture.
� Composition refers to the minerals of which rocks are formed.
� Texture means the shape, size, arrangement and distribution of the minerals that make up rocks.
� Both are evident in a rock’s appearance.
7
Igneous Rock Textures
� Igneous rocks have four basic types of
textures: glassy, fine-grained, coarse-
grained and porphyritic.
Glassy Igneous
� Glassy igneous rocks are shiny and look
like glass. The minerals that make up a
glassy igneous rock are not organized
into crystals. Obsidian has a glassy
texture.
Fine-Grained Igneous
� Fine-grained rocks, unlike glassy rocks,
are made of interlocking mineral crystals.
These crystals are too small to be seen
without the help of a microscope. The
dark gray rock known as basalt has a
fine-grained texture.
Coarse-Grained Rock
� Coarse-grained rocks, such as granite,
consist of interlocking mineral crystals,
which are all roughly the same size and
visible to the unaided eye.
8
Porphyritic Igneous Rocks
� Porphyritic rocks consist of large crystals
scattered on a background of much
smaller crystals. Sometimes these small
background crystals are too tiny to be
seen with a microscope. Porphyritic
rocks have a texture that resembles
rocky road ice cream.
Igneous Variety
� Where and how magma cools determines the size of mineral crystals. The longer it takes magma to cool, the larger are the crystals that form. Glassy and fine-grained rocks form from lava that erupts from volcanoes and hardens on the Earth’s surface. Coarse-grained rocks form from molten rock that cools and hardens within the Earth.
Extrusive Rocks
� Rocks formed from lava are called
extrusive rocks. Because lava is brought
to the surface by volcanoes, extrusive
rocks are also known as volcanic rocks.
Basalt and obsidian are two kinds of
extrusive rocks that are quite solid.
Pumice, another extrusive rock, is filled
with bubbles.
9
10
Intrusive Rocks
� Igneous rocks formed deep within the Earth
are called intrusive. They form when magma
forces its way upward into preexisting rocks
and then hardens. Intrusive rocks include
granite and pegmatite. Intrusive rocks are
also known as plutonic rocks. A mass of
intrusive rocks are known as a pluton. Plutons
may produce landforms by pushing up layers
of rock above them, such as domes.
Sedimentary Rock
� Most sedimentary rocks are formed from particles that have been carried along and deposited by wind and water. These particles, sediments or detritus, include bits of rock in the form of mud, sand or pebbles. Sediments also include shells, bones, leaves, stems and other remains of living things. Over time they are pressed together to form rocks.
11
Clastic
� The rocks that form by cementation or
compaction are known as detrital or
clastic sedimentary rocks.
� They are further subdivided by size of
the particles.
12
Chemical Sedimentary
� Chemical sedimentary rocks form from
solution
� An example would be rock salt or
gypsum.
Slowly Built Layers: Sedimentary
Rocks
� Igneous rocks are the most common
rocks on Earth but most of them exist
below the surface. 75% of the rocks
exposed at the surface are sedimentary.
13
Classification of Sedimentary
Rocks
� The most widely used classification
system for sedimentary rocks places
them into three main categories
according to the origin of the materials
from which they are made. These three
categories are: clastic or detrital rocks,
organic rocks and chemical rocks.
Clastic Rocks
� Sedimentary rocks that
are made of the
fragments of previously
existing rocks are
known as clastic rocks.
Clastic rocks classified
according to the size
and shape of the
fragments in them:
conglomerate,
sandstone and shale.
Conglomerates
� Some clastic rocks are made of rounded
pebbles cemented together by clay, mud
or sand. If over a third of the rock is
made of pebbles, the rock is called a
conglomerate. The pebbles in
conglomerates are smooth and rounded
because they have been worn down by
the action of water. They are also called
puddingstones. If the pieces of the rock
are angular then it is called breccia.
Sandstones
� Clastic rocks made of small, and-sized grains are called sandstones. At least half the particles in a clastic rock must be sand sized in order for it to be considered a sandstone. Sandstones are very common rocks. They are formed from the sand on beaches, in riverbeds and in sand dunes. In a sandstone, the grains are cemented together by minerals such as quartz, calcite and hematite, that harden.
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Shale
� Many geologists use term shale to
describe all the clastic rocks that are
made of particles smaller than sand.
Shale forms from small particles of mud
and clay that settle to the bottom of quiet
bodies of water such as swamps. Most
shale can be split into flat pieces.
Organic Rocks
� Organic rocks come from organisms. Limestone are often but not always organic rocks. Deposits of limestone may be formed from the shells of creatures when they die. Creatures may also cement their shells together and over time form reefs. Coal is also made from the remains of living things. It is made from plants that lived millions of years ago.
Coal and Coquina Chemical Sedimentary Rocks
� Water precipitates two ways to form
chemical sedimentary rocks
� 1. by the process of evaporation
� 2. through the life processes of marine
organism
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Biochemical Sedimentary Rocks
� Coral is an example
of a chemical
sedimentary rock
that was formed
through the life
processes of a coral
polyp.
Evaporites
� Halite and gypsum
are examples of
evaporates.
Chemical Rocks� Some sedimentary rocks are
formed when a sea or lake
dries up, leaving large
amounts of minerals that
were dissolved in water.
Examples of chemical rocks
formed this way include rock
salt and gypsum. Some
limestone rocks are formed
by inorganic processes in
caves. As water evaporates,
a thin deposit of limestone is
left behind.
Limestone- the most abundant
sedimentary rock
� Calcium carbonate is
carried in solution in
ocean water. When the
calcium carbonates
comes out of solution as
calcite, the crystals grow
together and lime stone
forms. Limestone is
50% calcite. Much is
found in Kansas which
was underwater.
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Rock Salt
When water that is rich in
salt evaporates, it
deposits the mineral
halite. Halite forms rock
salt. Rock salt deposits
can be as thick as 400
meters. Companies
mine these salts. It is
used in making glass,
paper, soap and dairy
products. The halite is
processed for table salt.
Inorganic Chemical Sedimentary
Rocks
� Travertine is an
inorganic chemical
sedimentary rock
that is found in
caves.
Silicates
� Chert, jasper and
flint all form from
silica that is left
behind when water
evaporates.
Sedimentary Rock Classification
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METAMORPHIC ROCKSMETAMORPHIC ROCKS
�� Metamorphism is the process by which Metamorphism is the process by which
the structure and mineral content of a the structure and mineral content of a
rock are changed while the rock remains rock are changed while the rock remains
in a solid state. in a solid state.
�� Contact metamorphismContact metamorphism
�� Shear metamorphismShear metamorphism
�� Regional metamorphismRegional metamorphism
�� FoliationFoliation
Changes in Form: Metamorphic
Rocks
� When already existing rocks are buried
deep within the Earth, tremendous heat,
great pressure and chemical reactions
may cause them to change into different
rocks with different textures and
structures. The changing of one type
rock into another as a result of heat,
pressure and /or chemical reactions is
called metamorphism.
Metamorphic Rocks
� Metamorphic rocks are formed when
chemical reactions, tremendous heat
and great pressure change existing
rocks into new kinds of rocks. These
new rocks have chemical and physical
properties usually quite different from the
original rocks.
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Metamorphic Rocks
� Metamorphic rocks may be formed from igneous, sedimentary or metamorphic rocks. Heat and pressure are great enough to make tock undergo change. Temperatures of 100 degrees to 800 degrees cause some minerals to break down, allowing their atoms to form other more heat-tolerant minerals.Texture, mineral and chemical composition may change.
19
Metamorphic Rocks
� The amount of heat, pressure and
chemical reactions varies during
metamorphism. Thus the degree of
metamorphism also varies. The
characteristics of the original rock also
affect the degree of metamorphism.
Many metamorphic rocks can be
produced from more than one kind of
rock.
Metamorphic Classification
� Like igneous and sedimentary rocks,
metamorphic rocks can be classified
according to texture. The classification
for metamorphic rocks are based on the
arrangement of the grains that make up
the rocks.
Foliated Rocks
� In the first group, the mineral crystals are
arranged in parallel layers, or bands.
The word foliated comes from the Latin
word for leaf. It describes the layers in
such metamorphic rocks, which are thin
and flat. Most metamorphic rocks are
foliated, like schist, slate and gneiss.
Unfoliated Rocks
� In the second, smaller group of
metamorphic rocks, the rocks are not
banded and do not break into layers.
These rocks are said to be unfoliated.
Marble and quartzite are examples of
unfoliated rocks.
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Elements, Compounds and
Mixtures
� Matter is anything that takes up space
and has mass.
� All matter can be classified into three
forms: elements, compounds and
mixtures.
Element
� An element is a substance that cannot be separated into simpler substances by ordinary chemical means. Scientists have identified 109 elements.
� Each element has a name and a chemical symbol made up of one or two letters.
� The smallest part of an element that has all the properties of that element is an atom.
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Molecules
� Some elements are made up of atoms
that are chemically combined to form
molecules.
� A molecule is two or more atoms held
together by chemical forces.
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Atomic Structure
� Atoms are made up of three main
particles: protons, neutrons and
electrons. The center of the atom is
called the nucleus. Two different kinds
of particles are found in the nucleus.
One of these is the proton.the proton is a
positively charged particle. The other
particle that makes up the nucleus is the
neutron. A neutron is a neutral particle.
Compounds
� A compound is made of atoms of
different elements that are bonded
together. Water is a compound. Some
compounds are made up of aluminum,
magnesium, silicon, oxygen and
hydrogen.
Mixtures
� Some forms of matter are neither elements nor
compounds. Instead they are two or more
substances mixed together. Such forms of
matter are called mixtures. A mixture is two or
more substances physically combined. Most
rocks, soil, sea water and air are examples of
mixtures. Because the substances that make
up a mixture are not chemically combined they
can be separated by physical means.
23
Chemical Formulas
� The combinations of chemical symbols
that represent atoms are called chemical
formulas.
� A chemical formula shows that elements
that make up a compound. A chemical
formula also shows the number of atoms
of each element in a molecule or
smallest particle of the compound.
Minerals
� A mineral is a naturally occurring,
inorganic solid that has a definite
chemical composition and crystal
structure. In order for a substance to be
called a mineral, it must have all of the
characteristics described in this
definition.
Inorganic
� A mineral must be inorganic, or not
formed from living thing or the remains of
living things.
Solid
� A mineral is always a solid. Like all
solids, a mineral has a definite volume
and shape.
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Chemical Composition
� A mineral has a definite chemical
composition. A mineral may made of a
single pure substance, or element, such
as gold, copper or sulfur. Most minerals
are made of two or more elements
chemically combined to form a
compound.
Crystal Structure
� A mineral’s atoms are arranged in a
definite pattern repeated over and over
again. Atoms not confined, the
repeating pattern of a mineral;s atoms
forms a solid called a crystal. A crystal
has flat sides that meet in sharp edges
and corners. All minerals have a
characteristic crystal structure.
� There are 2500 different kinds of
minerals.
Crystal Structure Crystals
25
Formation and Composition of
Minerals
� Many minerals come from magma, the molten rock beneath the Earth’s surface. When magma cools, mineral crystals are formed. How and where magma cools determine the size of the mineral crystals. When magma cools slowly beneath the Earth’s crust, large crystals form. When magma cools rapidly beneath the Earth’s surface, small crystals form.
Crystal Formation
� Crystals may also form from compounds
dissolved in a liquid such as water.When
the liquid evaporates, or changes to a
gas, it leaves behind the minerals as
crystals. Halite, or rock salt, forms in this
way.
Minerals can thus be classified into
the following major groups:
native elements, sulfides,
sulfosalts, oxides and hydroxides,
halides, carbonates, nitrates,
borates, sulfates, phosphates, and
silicates.
Rock Forming Mineral Groups
Chemical Classification Mineral Elements
Silicates Feldspar, Pyroxene,
Olivine, Mica, Quartz
Silicon, Oxygen
Carbonates Calcite, Dolomite Calcium Carbonate
Oxides Hematite Iron
Sulfates Gypsum Sulfur, Calcium
Halides Halite Sodium, Chlorine
26
Identifying Minerals
� Minerals have certain physical properties
that can be used to identify them, such
as color, luster, hardness, streak,
density, crystal shape, and other special
properties.
Color
� The color of a mineral is an easily
observed physical property. Color can
be used to identify only those few
minerals that always have their own
characteristic color, such as malachite
which is always green. The mineral
azurite is always blue.
� Many minerals come in a variety of
colors. Some are colorless.Colors can
also change.
Color The Many Colors of Quartz
27
Luster
� The luster of a mineral describes the way
a mineral reflects light from its surface.
Certain minerals have a metallic luster,
such as silver, copper and gold.
Minerals that do not reflect light have a
nonmetallic luster, and are described by
terms like glassy, pearly, dull and silky.
Metallic Luster
Non Metallic Luster Hardness
� The ability of a mineral to resist being scratched is known as its hardness. Hardness is one of the most useful properties for identifying minerals. Friedrich Mohs, a German mineralogist, worked out a scale of hardness for minerals ranging from 1 to 10. The number one is assigned to the softest mineral, talc and 10 is assigned to the mineral, diamond.
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Moh’s Scale
1-10
Streak
� The color of the powder scraped off a mineral when it is rubbed against a hard , rough surface is called its streak. The streak may be different from the color of the mineral. Streak can be observed by rubbing the mineral sample across a piece of unglazed porcelain, which is called the streak plate. A streak plate has a hardness slightly less than 7.
Streak
29
Density
� Density is the amount of matter in a
given space. The density of a mineral is
always the same, no matter what the
size of the mineral sample.
Crystal Shape
� Minerals have a characteristic crystal
shape that results from the way the
atoms or molecules come together as
the mineral is forming. There are six
basic shapes of crystal structures: cubic,
hexagonal, orthorhombic, monoclinic,
tetragonal and triclinic.
Crystal shape Cleavage and Fracture
� The terms cleavage and fracture are
used to describe the way a mineral
breaks. Cleavage is the tendency of a
mineral to split along smooth, definite
surfaces. Some minerals, like halite,
break into small cubes. Micas cleave
along one surface, making layers of thin
sheets. Most minerals do not break
along smooth lines.
30
CleavageFracture
Special Properties
� Some minerals can be identified by
special properties. Magnetite is naturally
magnetic. Fluorite glows under ultraviolet
light. Halite tastes salty. Sulfur smells
like rotten eggs. Calcite fizzes when
hydrochloric acid is added to . Uraninite
is radioactive.
31
Ores
� The term ores is used to describe
minerals or combinations of minerals
from which metals and nonmetals can be
removed in usable amounts.
Metals
� Metals are elements that have shiny
surfaces and are able to conduct
electricity and heat. Metals can be
pressed or hammered into thin sheets
and other shapes without breaking.
Metals cans also be pulled into thin
strands. Iron, lead, aluminum, copper,
silver and gold are examples of metals.
Smelting
� Most metals are found combined with
other substances in ores. After the ores
are removed from the Earth by mining,
the metals must be removed from the
ores. During a process, called smelting,
an ore is heated in such a way that the
metal can be separated from it. Metals
are useful. Copper is used in pipes and
electrical wire.
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Nonmetals
� Nonmetals are elements that have dull
surfaces and are poor conductors of
electricity and heat. Nonmetals are not
easily shaped. Some are removed from
the Earth in usable form. Others must
be processed. Sulfur,a nonmetal, is
used to make matches, fertilizers and
medicines.
Gemstones
� Gemstones are minerals that are hard, beautiful and durable and can be cut and polished for jewelry and decoration. Once a gemstone is cut and polished, it is called a gem. The rarest and most valuable gemstone- diamonds, rubies, sapphires and emeralds, are known as precious stones. All other gemstones, amethysts, zircons, garnets, are known as semiprecious stones.
KENALPASTI BATUAN, MINERAL ATAU ELEMEN
SECARA MIKROSKOPIK DAN MAKROSKOPIK
Identifying rocks in the field (hand sample)
� Relative hardness (Moh’s scale)
� Presence, type and size of minerals� chert versus rhyolite
� Color – some are distinctive
� Luster� metallic, vitreous, resinous, pearly, greasy, silky, adamantine, dull, earthy
� Streak (with a porcelain streak plate)
� Cleavage – good, poor
� Magnetism
33
Petrology
� How rock changes over time (weathering, erosion)
� Can help with determining age of material culture
� Source Areas (where raw materials originated)
� Thin Section Analysis
� Looking for characteristic inclusions and crystals
� Analysis of trade, exchange, social interaction, migration
� Trace Element Analysis
� X-Ray fluorescence, Neutron Activation Analysis, etc.
� Energize sample to stimulate emission of characteristic trace element
spectra; can then be tied to a source area
34
The PLM is a basic tool of the geologist. It exploits the fact
that most minerals are transluscent (i.e., if the mineral grain
is thin enough then the light will pass through). When using a
polarized light microscope an analyst examines light that
passes through a given sample and has interacted with the
internal structure of the mineral grains. When the light
emerges from the sample it has been altered due to
interactions within the mineral grains. Each mineral is unique
in its composition and/or structure so each mineral has a
unique affect on light when it passes through it. Thus
interpreting the emergent light allows a geologist to identify
minerals with great accuracy.
What Is A Polarized Light Microscope?
35
1) Light passes through the lower polarizer
west (left)
east (right)
Plane polarized light
PPL=plane polarized light
Unpolarized light
Only the component of light vibrating in E-W direction can pass through lower polarizer – light intensity decreases
2) Insert the upper polarizer
west (left)
east (right)
XN =crossed nicols (crossed polars)
south (front)
north (back)
Black!!
3) Now insert a thin section of a rock
west (left)
east (right)
Light vibrating E-W
Unpolarized light
Light vibrating in many planes and with many wavelengths
Light and colors reach eye!
Conclusion has to be that minerals somehow reorient the planes in which light is vibrating; some light passes through the upper polarizer
But, note that some minerals are better magicians than others (i.e., some grains stay dark and thus can’t be reorienting light)
36
4. Note the rotating stage
Most mineral grains change color as the stage is rotated (when the upper polarizer is in); these grains go black 4 times in 360° rotation - exactly every 90o
Glass and a few minerals stay black in all orientations
Glass and a few minerals stay black in all orientations
These minerals are anisotropic
These minerals are isotropic
Now do question 1Now do question 1
Isotropic
Uniaxial
Biaxial
How light behaves depends on crystal structure
Isometric– All crystallographic axes are equal
Orthorhombic, monoclinic, triclinic� All axes are unequal
Hexagonal, trigonal, tetragonal– All axes ⊥⊥⊥⊥ c are equal but c is unique
37
� Isotropic minerals: light does not get rotated or split; propagates with same velocity in all directions
� Anisotropic minerals:� Uniaxial - light entering in all but one special direction is resolved into 2 plane polarized components that vibrate perpendicular to one another Biaxial - light entering in all but two special directions is resolved into 2 plane polarized components…
� Along the special directions (“optic axes”), the mineral thinks it is isotropic - i.e., no splitting occurs
� Uniaxial and biaxial minerals can be further subdivided into optically positive and optically negative…
anisotropic minerals - uniaxial indicatrix
quartz
calcite
c-axis
c-axis
Mineral properties: color & pleochroism
• Color is observed only in PPL
• Not an inherent property - changes with light type/intensity
• Results from selective absorption of certain λ of light
• Pleochroism results when different λ are absorbed differently
by different crystallographic directions -
rotate stage to observe
plag
hbl
-Plagioclase is colorless-Hornblende is pleochroic in olive greens
plag
hbl
Mineral properties: Index of refraction (R.I. or n)
Light is refracted (bent) when itpasses from one substance to another;
refraction is accompanied by a change in velocity
n1n2n2
n1
n2>n1 n2<n1
n =velocity in air
velocity in mineral
• n is a function of crystallographic orientation in anisotropic minerals
� isotropic minerals: characterized by one RI
� uniaxial minerals: characterized by two RI
� biaxial minerals: characterized by three RI
• n gives rise to 2 easily measured parameters: relief & birefringence
38
Mineral properties: relief
• Relief is a measure of the relative difference in n
between a mineral grain and its surroundings
• Relief is determined visually, in PPL
• Relief is used to estimate n
olivine
plag
olivine: n=1.64-1.88
plag: n=1.53-1.57
epoxy: n=1.54
- Olivine has high relief
- Plag has low relief
What causes relief?
Difference in speed of light (n) in different materials causes refraction of light rays:
leads to focusing or defocusing of grains relative to their surroundings
nxtl > nepoxy nxtl < nepoxynxtl = nepoxy
Hi relief (+) Lo relief Hi relief (-)
Mineral properties: interference colors/birefringence
• Colors one observes when polars are crossed (XN)
• Color can be quantified numerically: δ = nhigh - nlowδ = nhigh - nlow
Use of interference figures, continued…Now determine the optic sign of the mineral:1. Rotate stage until isogyre is concave to NE (if biaxial)2. Insert gypsum accessory plate3. Note color in NE, immediately adjacent to isogyre --
� Blue = (+)� Yellow = (-)
Now determine the optic sign of the mineral:1. Rotate stage until isogyre is concave to NE (if biaxial)2. Insert gypsum accessory plate3. Note color in NE, immediately adjacent to isogyre --
� Blue = (+)� Yellow = (-)
uniaxial
biaxial
(+)
(+)
39
Most easily observed in PPL (upper polarizer out), but visible in XN as well
• No cleavages: quartz, olivine• 1 good cleavage: micas• 2 good cleavages:
amphiboles, pyroxenes
2 cleavages intersectingat ~90°pyroxene
60°120°
2 cleavages intersectingat 60°/120°: amphibole
Some new properties: Cleavage
Presence and style of twinning can be diagnostic
Twins are usually most obvious in XN (upper polarizer in)
Some new properties: Twinning Extinction angle - inclined extinction
Monoclinic and triclinic minerals: indicatrix axes do not coincide with crystallographic axes
These minerals have inclined extinction(and extinction angle helps to identify them)
clinopyroxene
extinction angle
40
Review – techniques for identifying unknown minerals
Start in PPL:• Color/pleochroism• Relief• Cleavages• Habit
Then go to XN:• Birefringence• Twinning• Extinction angle• Uniaxial or biaxial?• 2V if biaxial• Positive or negative?
41
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43
44
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The Electromagnetic Spectrum
� X-rays
� (Also gamma
rays)
X-rays
� What are X-rays? High energy photons.
� Note: gamma rays are just high-energy X-rays
� Advantages of X-ray spectrometric methods:
� The X-ray spectrum is not very sensitive to molecular effects or
chemical state, or excitation conditions
� This is because core electrons are usually involved in X-ray
transitions – physical and chemical state have only minute effects
(I.e. gas vs solid, oxide vs. element).
� Atomization is not necessary for elemental analysis
� Precision and accuracy are good, spectra are simple
� Surface-sensitive (penetration of 100 um at most)
� Disadvantages of X-ray methods:
� Surface-sensitive, if you want bulk analysis (often not a problem)
� Modest limits of detection, compared to other elemental methods
(e.g. AA, ICP-OES, ICP-MS)
is a non-destructive analytical technique used to
identify and determine the concentrations of
elements present in solid, powdered and liquid
samples.
XRF (X-ray fluorescence spectrometry)
46
X-ray Fluorescence (XRF) Spectrometry
� Review of the principles:
� if an X-ray photon (the primary X-ray) is absorbed
by an atom, and it has enough energy, it can
eject an electron, leaving a vacancy
� A higher energy electron will drop down to
replace it, emitting a “secondary” X-ray
� The energy of the secondary X-ray (if it can be
detected) is the difference of the binding energy
of the two shells!!!
� XRF is a similar process to the “photoelectric
effect” – where an x-ray is absorbed and
transfers all of its energy to an electron
X-ray Fluorescence
X-ray Generation: Characteristic Radiation XRF: Typical Spectra
� An ED XRF spectrum of a calibration standard:
47
Advantages and Disadvantages of XRF� Advantages:
� Can be applied in-situ and
nondestructively to analytes with
little or no sample preparation
� Speed – very fast
� Good accuracy and precision
� Disadvantages:� Not as sensitive as UV/Vis
methods for elemental analysis
(only gets down to ppm level in
some cases)
� Auger process reduces sensitivity
for lighter elements (Z < 23)
� Windows and other spectrometer
components can limit elements to
those with atomic numbers greater
than 5-6 (i.e. carbon) Philips PW2400 WDS
is a versatile, non-destructive technique that
reveals detailed information about the chemical
composition and crystallographic structure of
natural and manufactured materials.
X-ray diffraction (XRD)
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49
50
Wavelength-Dispersive Analyzers
� General layout of a WD X-ray monochromator
and detector:
“Sample”
(source of X-rays)
Wavelength-dispersing
crystal
Detector
(pulse height
detector)
θ
θ
Total = 2θ
θλ sin2dn =
d
n
2sin
λθ =
Reflection occurs when:
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52
SUMBANGAN
BIDANG GEOLOGI
DALAM KAJIAN
ARKEOLOGI
Jenis Kristal Jenis Konglomerat – Butiran Kasar dan
heterogenus
Jenis Butiran Besar dan Homogenus Jenis Butiran Halus dan
Homogenus
Sesuai dijadikan alat – hasilkan mata tepi yang
tajam
Pemilihan Bahan Mentah – Saiz Butiran
TEKNOLOGI LITIK
Pemilihan Bahan Mentah – Elastik
Batuan yang elastik sesuai untuk dibentuk sebagai alat
seperti obsidian, flin etc
Batuan yang tidak elastik akan berkecai apabila dibentuk
sebagai alat
TEKNOLOGI LITIK
Batuan kuarzit dengan 2 sifat yang berbeza telah dibuang semasa membua t a l a t , menunjukkan kefahaman masyarakat Paleolit ik tentang bahan mentah.
TEKNOLOGI LITIK
53
TEKNOLOGI LITIK
A photograph of iron rich limonite/hematite.
This sample ore is composed of quartz, which is
distinguished by the red geometric minerals. The
green is malachite and the light ret area is cuprite. The
shiny gold color is noted as copper and the dark
crimson region is iron. The black spots are sulfur.
The bright blue sections are azurite
crystals and the green part is malachite.
The brown areas are rock sediments.
An example of copper-
rich malachite ore
Delafossite needles on slag from furnace. Quartz on slag from furnace.
slag under the light microscope
it depicts structures called delafossite.
Delafossite is a type of mineral composed of
long needle-shaped crystals; they are evidence
of the smelting process.
We can tell that these are quartz because when the
slide is rotated, light causes it to change colors. If the
quartz is very shiny and sharp edged, then you know
that the ore was not heated to high enough
temperatures. If the quartz is molten on the edges, it
still probably was not heated high enough for it to melt
all the way.
SMELTING CRUCIBLES
This crucible contains quartz,
malachite, and iron oxide, proving
that it was used in the smelting
process.
This crucible was used for
smelting. We can make this
assumption because of the
slag deposits found on the
interior and exterior
surfaces of the artifact.
This picture is a model of what this crucible fragment would have
looked like in its complete form. The artifact found at the
archaeological site was only approximately 30% of the entire
crucible. A reconstruction using this piece would result in a
crucible about 10-11 cm. in diameter.
light
microscope
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Porous slag with copper Transitional slag.
Scanning Electron Microscope.
illustrates the porous nature of slag.
The bright spots, copper, are evidence
that smelting process was not
complete.
slag showed to be in a transitional stage. The
delafossite surrounds a denser area, which
may be slag that had melted and coagulated.
Composition of Slag
…good luck
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