The document discusses minerals and their properties. It defines a mineral as a naturally occurring, homogeneous, solid substance with a defined chemical composition and internal atomic structure. Minerals are building blocks of rock. The study of minerals is called mineralogy. There are over 4,900 known mineral species. Minerals form through igneous, sedimentary and metamorphic processes. Their identification is important for civil engineering applications when evaluating rock properties. Minerals can be identified by their physical properties like color, streak, luster, hardness, crystal structure, cleavage and density, as well as their chemical composition.

1. UNIT-2
MINERALS OF THE EARTH’S
CRUST

3. What is a Mineral?
• Definition: a 1homogeneous,
2naturally-occurring, 3solid, and 4
generally inorganic substance with
a 5definable chemical composition
and an 6orderly internal
arrangement of atoms
• It is a building block of rock
• Does not include “minerals” in the
nutritional sense

4. 1- Homogeneous
 Definition: Something that is the same through and through
Cannot be broken into simpler components
2- Naturally Occurring
 Minerals are the result of natural geological processes
 Man-made minerals are called synthetic minerals
Eg industrial diamonds
3- Solid
 Minerals must be able to maintain a set shape nearly
indefinitely
 liquids are not minerals

5. 4- Definable Chemical Composition
 A mineral can be described by a chemical formula
 Quartz: SiO2
 Biotite: K(Mg, Fe)3 (AlSi3O10)(OH)2
 Diamond: C
5 Orderly Arrangement of Atoms
• Minerals have a fixed atomic pattern that repeats itself over a
large region relative to the size of atoms
– Crystal solid, or crystal lattice: The organized structure of a
mineral
– A glass is not a mineral; no organized structure
6- Generally Inorganic
• Organic: A substance composed of C bonded to H, with
varying amounts of O, N and other elements. C, alone, is not
organic!
• Only a few organic substances are considered minerals, all other
minerals are inorganic

6. Mineralogy
A mineral is a naturally occurring substance that
is solid and stable at room temperature,
representable by a chemical formula, and has an
ordered atomic structure. The study of minerals
is called mineralogy, deals with their individual
properties, their mode of formation and mode of
occurrence.
There are over 4,900 known
mineral species; over 4,660 of
these have been approved by
the (IMA). International
Mineralogical Association

7. Mode of formation of minerals
• Basically there are three kinds of formation of minerals in
nature. They are formed from magma or out of secondary
processes or under metamorphism.
• Most of the minerals are formed directly or indirectly out of
magma during different stages of its solidification. Important
and bulky rock- forming minerals such as feldspar, quartz,
pyroxenes, amphiboles, micas, are formed these ways.
• Some precious minerals such as garnet, topaz, magnetite are
also formed from magmatic sources.

8. Mode of formation of Minerals
• In nature, some minerals are
from secondary processes
formed
like
weathering, precipitation and
deposition. Minerals like calcite,
dolomite, salts, coal, are example of this
group.
• Another important mode of formation of
minerals is out of metamorphism. These
minerals are formed under the influence
of high temperature and pressure with
or without active involvement of
chemically active solutions.

9. Civil Engineering Importance of
Rock forming minerals
• Undoubtly, among different minerals of economic minerals by
virtue of their utility and inherit values are very important.
However from civil engineering point of view, rock forming
minerals are very essential because:
• The civil engineers need to know the properties of rocks precisely
to enable them to consider different rocks for any required
purpose i.e. as a foundation rock, as a road metal, as
concrete aggregate, as building stones, as floorings, or
roofing minerals as decorative material.

10. Civil Engineering Importance of Rock forming
minerals
• Thus properties of rocks such as
strength, durability, and appearance of
rock can
knowledge
be assessed
of the minerals
only
that
with
form
rock. The economic minerals , since they
are scare, do not influence the properties
of rocks and hence irrelevant from civil
engineering point of view.

11. Different methods of study of minerals
• According to the definition, every mineral has its
own chemical
structure. This
composition
combination
and atomic
of chemical
composition and atomic structure is unique for
every minerals. This in fact facilitates the study
of minerals in different ways. Common methods
of study and identification of minerals are
• (i) Their physical properties
• (ii) Their chemical composition
• (iii) Optical methods
• (iv) X-ray analysis

12. Study of Physical Properties
• Physical properties of minerals like color, shine,
hardness, density,etc can be studied with mere
observation of small mineral specimen.
• Since the minerals invariably possess its own
specific chemical composition and atomic
structure every minerals should possess its own
physical properties.

13. Study of Chemical Composition
• According to the definition, every mineral is expected
to have its own distinctive chemical composition,
which is not to be found in any other mineral. Therefore,
by chemical analysis, if the composition is known it
should be possible to identify the minerals.

14. The Physical properties of minerals are
used by Mineralogists to help determine the
identity of a specimen.
• Some of the tests can be performed easily
in the field, while others require lab
equipment.
The Physical Properties of Minerals

15. The Physical Properties of
Minerals
• Color
• Streak
• Luster
• Hardness
• External Crystal Form
• Cleavage

16. The Physical Properties of Minerals
(cont.)
• Fracture
• Specific Gravity
• Special Properties
• Degree of Transparency
• Other Properties
• Chemical Tests

17. Mineral Identification
• Since we can‟t all have x-ray diffraction machines and electron
microscopes, we identify minerals by visual and chemical
properties called physical properties.
Gravity,
• Types of physical properties that geologists use include:
– Color, Streak, Luster, Hardness, Specific
Crystal Habit, and Cleavage
Pyrite
 Properties depend upon…
 Chemical composition.
 Crystal structure.
 Some are diagnostic.
 Minerals have a unique set of
physical properties.

18. 1- Color
Various colors of quartz, SiO2
Hematite (Fe O ) can have various colors, but its
2 3
streak is always red-brown
• Color may be diagnostic
for a few minerals, but in
general, a given mineral
can have a range of colors.
2- Streak
 The color of the pulverized
powder of a mineral.
 More consistent than
color
mineral against
 Found by scraping a
a
porcelain plate

19. Important Physical Properties
• Color - Although an obvious feature, it is
often unreliable to use to determine the
type of mineral.
 Color arises due to electronic transitions,
often of trace constituents, in the visible
range of the EM spectrum. For example,
quartz is found in a variety of colors.
• Color of a mineral may be quite
diagnostic for the trace element and
coordination number of its bonding
environment.

20. Color
• Colour : Colour is the first thing someone
notices when they view a mineral. Color is also
one of the big reasons that attract people to
minerals. Generally speaking, color is not a
good property to be used in the identification of
minerals. It is usually the
confuse a novice collector
first property to
into making an
incorrect identification.
• Minerals having Property of Green, Golden
Yellow, Yellow, White, Red, Blue, Black, Grey,
Purple & Transparent Colour.

21. Color

22. Color

23. Important Physical Properties
• Streak - The color of a mineral in
its powdered form;
rubbing the mineral
obtained by
against an
unglazed porcelain plate.
• Streak
color.
• Useful
is usually less variable than
for distinguishing between
minerals with metallic luster.

24. Streak

25. 3- Luster
• The way a mineral‟s
surface scatters light
Metallic luster
4- Hardness
• The measure of a mineral
to resist scratching
• Represents the strength of
bonds in the crystal lattice
– Measured on a qualitative
scale called Mohs
Hardness Scale
Nonmetallic luster
Vitreous
luster
(Nonmetallic)
Adamantine luster
(Nonmetallic)
• It is the shine of the mineral.

26. Important Physical Properties
• Luster - This property describes
the appearance of reflected light
from the mineral's surface.
Nonmetallic minerals are described
using the following terms: vitreous,
pearly, silky, resinous, and earthy.

27. Luster
Lustre is a description of the way a mineral surface
looks when light reflects off of the surface.

28. Luster

29. Important Physical Properties
• Hardness - This is the resistance of the mineral to
abrasion or scratching. This property doesn't vary
greatly from sample to sample of the same mineral,
and thus is highly diagnostic. It also is a direct
reflection of the bonding type and internal atomic
arrangement. A value is obtained by comparing the
mineral to a standard scale devised by Moh, which is
comprised of 10 minerals ranging in hardness from
talc (softest) to diamond (hardest).

30. Mohs’ Hardness
Scale

31. Hardness
a mineral
• The hardness of
describing how easy or difficult it is
scratch the mineral.
with the
is a way of
to
It is used, in
other physical
to help identify a mineral
combination
properties,
specimen

32. Mohs scale of mineral
hardness
• The Mohs scale of mineral hardness
characterizes the scratch resistance of various
minerals through the ability of a harder
material to scratch a softer material.
created in 1812 by the
geologist and mineralogist Friedrich
• It was
German
Mohs.

33. Mohs scale of mineral hardness

34. Mohs scale of mineral hardness
• The Mohs scale of mineral hardness is based on the
ability of one natural sample of matter to scratch another
mineral. The samples of matter used by Mohs are all
different minerals. Minerals are pure substances found in
nature. Rocks are made up of one or more minerals. As
the hardest known naturally occurring substance when
the scale was designed, are at the top of the scale. The
hardness of a material is measured against the scale by
finding the hardest material that the given material can
scratch, and/or the softest material that can scratch the
given material.

35. Mohs scale of mineral
hardness

36. Mineral Hardness
The Moh's Scale of Hardness:
Talc Gypsum Calcite
Fluorite Apatite Orthoclase Feldspar

37. Mineral Hardness
The Moh's Scale of Hardness:
Topaz
Quartz Corundum
Diamond

38. 5- Specific Gravity
 Specific Gravity: The weight of a substance
divided by the weight of an equal volume of water
6- Crystal Habit
• A description of a mineral‟s
consistent shape
Prismatic
Blade-like or
Elongated
Needle-like or
fibrous

39. Density and Specific Gravity
• Density - Defined as the mass divided by the
volume and normally designated by the
Greek letter, rho, Mass/ Volume; SI units: kg/m3
or kg m-3, but geologists often use g/cm3 as the unit
of choice.
• Specific Gravity - Ratio of the mass of a
substance to the mass of an equal volume of
water. S.G. is unit-less.
• Examples - quartz (SiO2) has a S.G. of 2.65
while galena (PbS) has a S.G. of 7.5 and gold
(Au) has a S.G. of 19.3.

40. Specific Gravity
• Specific Gravity : Specific Gravity of a
mineral is a comparison or ratio of the
weight of the mineral to the weight of an
equal amount of water. The weight of the
equal amount of water is found by
finding the difference between the weight
of the mineral in air and the weight of
the mineral in water.

41. Specific Gravity
• Specific Gravity (G) = mass of subs./mass of
equiv. Vol. H2O at 4ºC
• Silicates ~ 2.5
• Gold ~ 19
• Galena ~ 7.5
• 45
• Specific Gravity is a „way‟of expressing density.
• Density: weight/unit volume (g/cm3)

42. Crystal Form
 Crystal form is the external expression of the internally ordered arrangement
of atoms.
 During mineral formation, individual crystals develop well-formed crystal
faces that are specific to that mineral.
 The crystal faces for a particular mineral are characterized by a symmetrical
relationship to one another that is manifest in the physical shape of the mineral‟s
crystalline form.
 Crystal forms are commonly classified using six different crystal systems, under
which all minerals are grouped.
The six major crystal forms:
1. Isometric (Cubic)
2. Tetragonal
3. Orthorhombic
4. Hexagonal
5. Monoclinic
6. Triclinic
Axes and Angles
C
B

A

43. Fracture and Cleavage
• Cleavage: The tendency of a
mineral to break along a plane of
weakness in the crystal lattice.
• Fracture: The mineral breaks in
no consistent manner
– Equal bond strength in all
directions
• Conchoidal Fracture: The
tendency for a mineral to break
along irregular scoop-shaped
fractures that are not related to
weaknesses in the crystal
structure
Obsidian, a volcanic glass, and
quartz commonly exhibit conchoidal
fracture, which is why Indians used
them as cutting tools.

44. Important Physical Properties
• Cleavage - Orientation and number of planes of
weakness within a mineral. Directly reflects the
orientation of weak bonds within the crystal
structure. This feature is also highly diagnostic.
• Fracture - This describes how a mineral breaks if
it is not along well defined planes. In minerals with
low symmetry and highly interconnected atomic
networks, irregular fracture is common.

45. Planer Cleavage in Mica

46. Cleavage
• Tendency to break along planes of weakness.
• Cleavage produces flat, shiny surfaces.
• Described by number of planes and their angles.
• Sometimes mistaken for crystal habit.
– Cleavage is through-going; often forms parallel “steps.”
– Crystal habit is only on external surfaces.
• 1, 2, 3, 4, and 6 cleavage planes possible.

47. Cleavage
 Examples of
Cleavage:
 1 direction
 2 directions at 90º
 2 directions NOT at
90º
Muscovite Mica
Amphibole
Potassium Feldspar

48.  Examples of Cleavage:
 3 directions at 90º
 3 directions NOT at 90º
Cleavage
Calcite
Halite

49. Cleavage

50. Fracture