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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

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� Mining, smelting, and casting became organized efforts.

Iron Age Tools

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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.

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�� 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.

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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

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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

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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

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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

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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

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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.

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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.

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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

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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

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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?

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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)

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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

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� 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

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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

(+)

(+)

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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

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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?

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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)

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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:

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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