Lect2 geology-02

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Rock, soil and Minerals
Instructor:
Engr Muhammad Khubaib
Lecture # 3
Department of Civil Engineering
City University of Science and IT Peshawar.

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1. Rock, soil and Minerals
2. Identification of minerals: Physical properties
3. Common rock forming minerals
Outlines of the Presentation

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Week Topic/Lecture Lecture Objectives Learning
Outcomes
Delivery
(Hours)
Assessment
( Tools)
Course Program Lec Tutorial IS CP CBA TA
1 Introduction to
Geology:
The Earth as a
planet, Process of
external and
internal origin
(Volcanic,
Metamorphic,
Sedimentary)
- Introduction to
Geology and
Engineering
- Introduction to
various theories
about formation of
earth
- To identify
various layers of
Earth and its
significance of
Engineering
- Significance of
Engineering
Geology
CLO-1 PLO-1 02 01 02 X X
Assignment/Activity:
Visit website and some videos on
the formation of earth.
Team Assignments:
1. Various theories on the
formation of earth
2. Interior of earth
3. The role of earth crust in
human development
4. Relation of earth curst with
Civil Engineering
5. Role of Engineering
Geology in the Civil
Engineering Practice
6. Branches of Engineering
Geology
7. Various Engineering
problems associated with
geological Changes
8. The challenges in
Engineering geology

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Minerals are naturally occurring inorganic substances of more or less definite
chemical composition, displaying more or less definite physical properties and
regular crystalline structure.
A mineral is a naturally occurring solid formed through geological processes that
has a characteristic chemical composition, a highly ordered atomic structure, and
specific physical properties.
The study of minerals is called mineralogy.
However, the International Mineralogical Association in 1995 adopted a new
definition:
A mineral is an element or chemical compound that is normally crystalline and
that has been formed as a result of geological processes.
Minerals and Rock

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Rocks: A rock, by comparison, is an aggregate of minerals and/or
mineraloids, and need not have a specific chemical composition.
Minerals range in composition from pure elements and simple salts
to very complex silicates with thousands of known forms.
Geologist define rock as aggregates or mass composed of one or
more commonly, several of minerals. There are few exceptions to
this rule: not all rocks are composed of minerals-for example, coal.
Engineers (or contractor) define rock to be a ‘hard, durable material
that can’t be excavated without blasting’. The definition is based on
strength and durability.
Can you name some names of Rocks and Minerals?
Minerals and Rock

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• Minerals
are naturally occurring inorganic substances of more or less definite
chemical composition, displaying more or less definite physical properties.
• Some minerals are very strong and resistant to deterioration and produce
rock with similar properties, while others are much softer and produce
weaker rock.
• More than different 2000 minerals are present in the earth’s crust.
They can be identified by their physical and chemical properties; by
standard tests; or by examination under microscope.
Minerals and Rock

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1. Color
2. Streak
3. Hardness: Mohs scale of hardness
4. Cleavage
5. Fracture
6. Luster
Identification of minerals

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➢ Color:
✓ Color indicates the appearance of the mineral in reflected light or transmitted light for
translucent minerals (i.e. what it looks like to the naked eye).
✓ Some minerals have characteristics color due to composition of the minerals and the
arrangement of the constituent atoms: for example black color of magnetite, green
COLOR of chlorite and brassy yellow color of pyrite.
✓ Minerals like quartz and calcite have variable color.
✓ Color can’t be sole identification property
✓ Color change with impurities present. For example Quartz, which is colourless when
pure, may be white, grey, pink or yellow, when certain chemical impurities or
included particles are present.

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Streak
Color of mineral in powder (pulverized) form is called streak
Powder is obtained by crushing the mineral. Or the minerals may be rubbed
against unglazed porcelain streak plate to obtain the streak.
Color of the streak differs from color of mineral: for example the color of pyrite
is brass yellow and its streak is dark green.

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➢ Cleavage:
✓ The cleavage of the minerals is its capacity to split more readily in certain
directions than in others, due to the arrangement of the atoms.
✓ Minerals break with ease producing smooth surfaces is called perfect cleavage. It can be
either good, distinct, indistinct and imperfect.
✓ Some minerals such as mica have perfect cleavage in one direction. The
feldspars, which is the most abundant of all minerals, have two cleavages.
Cleavage NO cleavage

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➢ Luster:
How shinny the mineral is. The quality and intensity of light that reflects from a mineral
Metallic – shines like a polished metal
Vitreous – shines like glass
Pearly – shines like a pearl
Resinous – shines like the surface was covered by oil or grease.
➢ Appearance of mineral in ordinary light (that is the appearance due to reflected
light). Luster may be metallic, glassy, earthy, pearly or silky.
➢ If the minerals looks metal as do galena and pyrite, its luster is said to be metallic.
If the minerals looks glassy, like quartz, its luster is glassy.
Non-metallic mineral Metallic mineral

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Fracture
The nature of a broken surface of a mineral is known as fracture, but
the breaking should be in any other direction than the cleavage.
Minerals that have no cleavage commonly have an irregular fracture.
Quartz and garnet show conchoidal (curved surface) fractures. But
they also show irregular fracture.
Irregular Fracture Conchoidal Fracture

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➢ Hardness:
– The hardness of a mineral, as commonly determined on fresh material,
is measured by its ability to resist scratching. If a mineral is scratched
by a knife, it is softer than the knife. If it cannot be scratched by a knife,
the two are equal hardness or the mineral is the harder.
– Hardness is tested by attempting to scratch the minerals of the scale
with the specimen under examination.
– In order to have a standard method of expressing hardness of minerals, a
simple scale, known as the Mohs scale, has been universally adopted.

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➢ In sequence of increasing hardness from 1 to 10, the following minerals
are used as standard of comparison:
Talc 01 - Gypsum 02 - Calcite 03 - Fluorite 04 - Apatite 05 Orthoclase
(feldspar) 06 - Quartz 07 -Topaz 08 - Corundum 09 and Diamond -10
➢ A mineral which scratches calcite, for example, but not fluorspar, is said to have a
hardness between 3 and 4, or H = 3-4. Talc and gypsum can be scratched with a
finger-nail, and a steel knife will cut apatite (5) and perhaps feldspar (6), but not
quartz (7). Soft glass can be scratched by quartz. The hardness test, in various forms,
is simple, easily made, and useful; it is a ready means for distinguishing, for example,
between quartz and calcite.
Dorry test:
• Dorry's testing machine is used for hardness test of stones.
• The test measures resistance of aggregates to surface wear by abrasion.
The test involves in subjecting a cylindrical specimen of 25 cm height and 25
cm diameter to the abrasion against rotating metal
disk sprinkled with quartz sand.

Specific Gravity
Specific Gravity means the weight of a substance compared with the weight
of an equal volume of water. The specific gravity of quartz is 2.65. Some
minerals are heavier than the others. The specific gravity of majority minerals
range from 2.55 to 3.2.
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➢ Other Characteristics:
➢ Crystal Form: Internal atomic arrangement in definite geometric
patterns is sometimes outwardly expressed in crystal form.
➢ Magnetism: A few minerals are attracted by a magnet. Of these minerals,
magnetite, and pyrrhotite are the most common examples.
➢ Other properties:
✓ Fluorescence (response to ultraviolet light),
✓ Radioactivity, tenacity (response to mechanical induced changes of shape or form),
✓ Piezoelectricity ( Can generate electric fields) and
✓ Reactivity to dilute acids.
Reaction to Dilute Hydrochloric Acid
Carbonate minerals, especially calcite, may be identified by their reaction with
dilute HCl. This reaction is in the form of rapid bubbling, or effervescence, as
carbon dioxide is released. Non-carbonate minerals do not react to HCl.

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Pyrrhotite
Calcite Minerals

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Quartz- Carbonate class
Hallite- Oxide class
Kohinoor-Diamond

• Basic/Primary minerals (Silicate minerals)
– The olivine group
– The pyroxene group
– The amphibole group
– The mica group
– The feldspar group
– The feldspathoid group
• Accessory minerals
– Minerals that occur as small crystals and in limited quantities are described as
accessory
• Secondary minerals
– Described under this head are the minerals chlorite, serpentine, talc, kaolin, epidote and
zeolite, all of which result from the alteration of pre-existent minerals
• Clay minerals: Clays can form as either primary or secondary minerals. Here they
are grouped under one heading because of their economic importance,
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Rock Forming Minerals

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➢ Feldspars:
Feldspar is the most abundant minerals. There are two types. Orthoclase feldspars
contain potassium (KalSi3O8) and usually range from white to pink. Plagioclase
feldspars contain sodium (NaAlSi3O8), calcium (CaAl2Si2O8) or both, and range
from white to gray to black,. Feldspars have moderate hardness.
Uses:
Feldspar is a common raw material used in glassmaking, ceramics, and to some extent as a
filler and extender in paint, plastics, and rubber. In glassmaking, alumina
from feldspar improves product hardness, durability, and resistance to chemical corrosion.

• Quartz is also very common ingredient in many kinds of rock. It is silicate (SiO2),
and usually has a translucent to milky white color. The luster is vitreous. Quartz is
harder than most minerals (hardness 7), and thus is very resistant to weathering.
Chert is a type of quartz sometimes found in sedimentary rocks. It can cause
problem when used as concrete aggregate.
– Transparent Rock Crystal has many electronic uses; it is used as oscillators in radios, watches,
and pressure gauges, and in the study of optics. Quartz is also used as an abrasive for
sandblasting, grinding glass, and cutting soft stones
– Difference B/W Quartz and Quartzite
• The biggest difference between quartz and quartzite is that quartz is a man-made
material, while quartzite is a natural stone. ... A quartz countertop is engineered with the
same quartz crystals found in quartzite, but a man-made process binds the crystal with
resins, pigments, and other materials such as bits of glass.
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Mica:
Translucent (semitransparent) thin sheets or flakes. There are two common varieties.
Muscovite is potassium aluminum silicate of colorless or silvery tint, pearly luster and
especially one very perfect cleavage.
Biotite, the other common variety, is a complex silicate of potassium, magnesium and
iron and aluminum.
Biotite and muscovite are similar in physical properties. Both are soft, 2.5-3, with one
perfect cleavage.
The sheets of mica have very low coefficient of friction, which can produce shear failure in
certain rocks, such as schist (pronounced as shist).
• Uses of mica?
– It is used in paints as a pigment extender and also helps to brighten the tone of
colored pigments.
– In the electrical industry the same as thermal insulation, and electrical insulators in
electronic equipment.
– Its shiny and glittery appearance makes it ultimate for toothpaste and cosmetics.

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➢ Mica: Biotite and muscovite are similar in physical properties. Both are
soft, 2.5-3, with one perfect cleavage. The sheets of mica have very low
coefficient of friction, which can produce shear failure in certain rocks,
such as schist.
➢ Ferromagnesian minerals: A class of minerals, all of which contain both
iron and magnesium. This class includes pyroxene, amphibole, hornblende
and olivine. These minerals are dark color and a moderate hardness.
Muscovite Flakes
Biotite Flakes

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➢ Calcite:
A mineral made of calcium carbonate (CaCO3). It is usually white, pink or gray. It is
soluble in water, and thus can be transported by ground water into cracks in rock where
it precipitate out of solution. It also can precipitate in soil, becoming a cementing
agent. Calcite is much softer then quartz or feldspar. The hardness is 3. Have vigorous
reaction to hydrochloric acid.
➢ Dolomite:
Dolomite is a sedimentary rock.
Similar to calcite with magnesium added. Less vigorous reaction to dilute
hydrochloric acid.
Calcite Minerals

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➢ Iron Oxides:
Another class of minerals, all of which contain iron (FeO3). The most common iron
oxides are hematite, Fe2O3 ; hydrous iron oxide that are often called limonite and
magnetite. Although less common, these minerals give a distinctive rusty color to
some rocks and soils and can act as cementing agents. The compact varieties have a
hardness of 5.5-6, but earthy form are soft. The luster is sub-metallic.
➢ Gypsum:
A soft minerals often occurring as a precipitate in sedimentary rocks. It is colorless to
white and has economic value when found in thick deposits. For example, it is used to
make drywall. Gypsum is water soluble and thus can dissolve under the action of
ground water, which can lead to other problems.

Role of Geological Survey of Pakistan
• The Geological Survey of Pakistan is responsible for the study of
geology of the country in all pertinent details and to assess its
geological resource potential.
• It undertakes:
– Geological mapping and other geoscientific surveys,
– Basic and applied research in earth sciences,
– Scientific investigations for an accurate understanding of
the country’s geological resources and their prudent
management, and
– Environmental geology and hydrogeological studies
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