Civil Engineering Geology_Study of Mineralogy

A mineral is a naturally-occurring, homogeneous, solid with a definite, but generally not fixed, chemical composition and an ordered atomic arrangement.

1. MINERALOGY
FRANCIS W.

2. MINERALOGY
Definition:
•This deals with the study of minerals.
•Mineralogy deals with the detailed mode of formation, composition, occurrence,
types, associated properties uses, etc.

3. MINERALOGY
Definition:
A mineral is a naturally-occurring, homogeneous, solid with a definite, but generally
not fixed, chemical composition and an ordered atomic arrangement.
It is usually formed by inorganic processes.

4. MINERALOGY
Define Minerals
1.Natural
➢Occurs naturally
➢NOT manmade

5. MINERALOGY
Define Minerals
1.Natural
2.Homogeneous
✓Something that is the same throughout.
✓Cannot be broken into simpler components

6. MINERALOGY
Define Minerals
1.Natural
2.Homogeneous
3.Solid
✓Minerals must be able to maintain a set shape nearly indefinitely
✓liquids are not minerals.

7. MINERALOGY
Define Minerals
1.Natural
2.Homogeneous
3.Solid
4.Chemical Composition
➢A mineral can be described by a chemical formula
–Quartz: SiO
2
–Biotite: K(Mg, Fe)
3 (AlSi
3O
10)(OH)
2
–Diamond: C

8. MINERALOGY
Define Minerals:
5. Orderly Arrangement of Atoms
➢Minerals have a fixed atomic pattern where atoms are arranged
in a repeating and organized structure.
➢This repeating structure extends over a large region compared
to the size of individual atoms.
➢This regular and repeating pattern is known as the crystal lattice
and gives minerals their unique geometric shapes and physical
properties, such as cleavage, hardness, and density.
➢Minerals are crystalline solids, meaning their atoms are arranged
in a regular three-dimensional framework
➢A glass is not a mineral; not organized

9. MINERALOGY
Define Minerals:
6. Generally Inorganic
➢Most minerals are inorganic, meaning they do not originate from living
organisms or biological processes.
➢Organic: A substance composed of C bonded to H, with varying amounts of O,
N and other elements, eg., Proteins, fats, and sugars. C, alone, is not organic!
➢A few organic substances, such as certain carbonates or hydrocarbons like
amber and oxalates, may be classified as minerals if they meet other mineral
criteria (e.g., crystalline structure), all other minerals are inorganic

10. MINERALOGY - MINERAL IDENTIFICATION
Mineral Identification
Minerals are primarily identified based on their physical properties and chemical
characteristics, which can be observed and tested without specialized equipment
like X-ray diffraction machines or electron microscopes.
These methods make mineral identification accessible to a wide range of people,
from geologists to hobbyists.

11. PHYSICAL PROPERTIES OF MINERALS
Physical Properties of Minerals
1.Forms and Habits
2.Colour
3.Streak
4.Lustre
5.Fracture
6.Cleavage
7.Hardness
8.Specific Gravity
9.Degree of Transparency
10.Special Properties

12. PHYSICAL PROPERTIES -FORMS AND HABITS
Forms and Habits
The form represents the common mode of occurrence of a mineral in nature.
It is also called Habit or Structure of minerals.
To some extent this is the function of the atomic structure of minerals.

13. PHYSICAL PROPERTIES -FORMS AND HABITS
Lamellar Form
Mica
Minerals appears as Thin separable Layer
Tabular Form
Feldspar
Minerals appears as slab of uniform Thickness

14. PHYSICAL PROPERTIES -FORMS AND HABITS
Fibrous Form
Asbestos
Minerals appears to be made of Thin Thread

15. PHYSICAL PROPERTIES -FORMS AND HABITS
Pisolitic Form
Bauxite
Minerals appears to be made of small spherical grain

16. PHYSICAL PROPERTIES -FORMS AND HABITS
Oolitic Form
Lime stone
Minerals appears to be made of still small spherical grain

17. PHYSICAL PROPERTIES -FORMS AND HABITS
Rhombic Form Granular Form
Calcite
Minerals appears to be made of Rhombic
Shape
Minerals often appear as aggregates composed
of countless equidimensional grains that can
vary in size, ranging from coarse to medium
grains.
Magnetite, Chromite

18. PHYSICAL PROPERTIES -FORMS AND HABITS
Bladed Form
Botryoidal Form
Minerals appears as a cluster or independent
lath shaped grains.
Lath-shaped grains are thin, elongated crystals
resembling flat blades or needles.
Kyanite
Minerals appears as made up of smaller curved
faces like bunch of grapes.
Hematite, Chalcedony

19. PHYSICAL PROPERTIES -FORMS AND HABITS
Acicular Form Columnar Form
Minerals appears as made up of thin
needles.
Natrolite, Actinolite
Minerals appears as Long slender prism.
Quartz, Apatite

20. PHYSICAL PROPERTIES -FORMS AND HABITS
Prismatic Form Spongy Form
Minerals appears as elongated independent
crystals.
Quartz, Apatite
Minerals appears as porous
Pyrolusite, Bauxite, pumice

21. PHYSICAL PROPERTIES -FORMS AND HABITS
Crystal Form
Minerals appears as Polyhedral
Geometrical shapes
Quartz, Amethyst, Pyrite, Galena

22. PHYSICAL PROPERTIES -FORMS AND HABITS
Nodular Form
Irregular shaped compacted body With curved
surface
Flint, Lime stone

23. PHYSICAL PROPERTIES - COLOUR
Colour
•Colour is due to the composition.
•In some others it is imparted by the presence of
trace element, inclusions, atomic structure.
•Determined by the chemical composition of the
mineral
•Minerals rich in Al, Ca, Na, Mg are often light
coloured.
•Minerals rich in Fe, Ti, Ni, Cr are often dark in
colour

24. PHYSICAL PROPERTIES - COLOUR

25. PHYSICAL PROPERTIES - COLOUR
Colour
Determined by the atomic structure of the mineral
Atomic structure controls which components of white light are absorbed or
reflected
White minerals reflect all components of white light
Black minerals absorb all components of white light
Green minerals reflect green light and absorb the others

26. PHYSICAL PROPERTIES - COLOUR
Colour:
Colour is not particularly useful as a diagnostic property
Some minerals show a wide variety of colours
Quartz can be transparent, white, pink, brown, purple, yellow, orange and even black
Many minerals show very similar colours
Calcite, gypsum, Barytes, fluorite, plagioclase feldspar and halite are commonly grey
or white in colour

27. PHYSICAL PROPERTIES - COLOUR

28. PHYSICAL PROPERTIES - STREAK
Streak
•The colour of a mineral’s powder obtained by rubbing a mineral specimen on an
unglazed white porcelain tile known as a streak plate.
•This property is a reliable diagnostic tool for identifying minerals, as the streak
often remains consistent even when the surface color of the mineral varies due
to impurities or weathering.
•Useful for identifying metallic ore minerals.
•Silicates generally do not mark the tile and have no streak.
•White minerals streaked on a white tile will have a white streak

29. PHYSICAL PROPERTIES - STREAK

30. PHYSICAL PROPERTIES - STREAK

31. PHYSICAL PROPERTIES - LUSTRE
Lustre
•The way a mineral's surface reflects light and it is Controlled by the atomic
structure of the mineral.
•It is one of the key physical properties used in mineral identification and helps
describe the mineral's appearance based on the quality and intensity of the
reflected light.
•Lustre is the nature of shining on the surface of minerals.
•Based on quality or type of shining, lustres are grouped as metallic and non
metallic.

32. PHYSICAL PROPERTIES - LUSTRE
Non-Metallic:
Includes a variety of appearances that do not
resemble metals:

33. PHYSICAL PROPERTIES - LUSTRE

34. PHYSICAL PROPERTIES - FRACTURE
Fracture
•Fracture refers to the way a mineral breaks when it does not break along its
planes of cleavage.
•Unlike cleavage, which produces smooth, flat surfaces due to atomic alignment,
fracture results in irregular or curved surfaces.
•It is an important physical property used in identifying minerals.
•Fracture is a mineral property where the atomic bonding between atoms in
crystal structure is perfect with no weakness.
•When these minerals are stressed they shatter making no two pieces truly the
same.

35. PHYSICAL PROPERTIES - FRACTURE
Fracture
•Fracture occurs in the minerals where
bond strength is generally the same in
all direction.
•Minerals that have fracture do not
exhibit cleavage.
•Fracture is the Uneven breakage of
minerals.

36. PHYSICAL PROPERTIES - FRACTURE
•Fracture is defined as the appearance of broken surface of a mineral in a direction
other than the cleavage direction.

37. PHYSICAL PROPERTIES - FRACTURE

38. PHYSICAL PROPERTIES - FRACTURE

39. PHYSICAL PROPERTIES - CLEAVAGE
Cleavage
•Cleavage refers to the tendency of a mineral to break along specific planes of
weakness in its crystal structure.
•These planes are determined by the arrangement and bonding of atoms within
the mineral.
•When a mineral is struck, it may split along these planes to produce smooth, flat
surfaces.
•It is related to crystallinity only crystalline minerals have cleavage.
•Cleavage represents the plane of weakness in atomic structure of minerals.

40. PHYSICAL PROPERTIES - CLEAVAGE

41. PHYSICAL PROPERTIES OF MINERALS – TENACITY
Tenacity
•Tenacity refers to a mineral's resistance to breaking, bending, or deforming under
stress.
•It describes how a mineral reacts to external forces such as pressure, impact, or
pulling.
•Tenacity is an important property in determining a mineral's durability and how it
will behave in various environments.

42. PHYSICAL PROPERTIES OF MINERALS – TENACITY
Hardness
•Hardness is the measure of a mineral's ability to resist scratching or abrasion.
•It is one of the most important physical properties used to identify minerals.
•The hardness of a mineral is determined by the strength of the bonds between its
atoms and how easily the mineral can be scratched by other substances.

43. PHYSICAL PROPERTIES - HARDNESS
Hardness
•Hardness may be defined as the
resistance offered by minerals to
abrasion or scratching.
•Its is also related to Atomic structure
of Minerals.
•The chemical composition of mineral
appear to have a less influence over
hardness.
•Hardness in minerals is studied either
as Absolute hardness and Relative
hardness.
•Absolute hardness means Total
hardness.
•Relative hardness means comparative
hardness.
•The relative hardness of an unknown
mineral is determined through a
scratch test, where the unknown
mineral is scratched with minerals of
known hardness from the Mohs
Hardness Scale. The process begins
with Talc (hardness 1) and
progresses through the other minerals
on the scale.

44. PHYSICAL PROPERTIES - HARDNESS
Hardness
Steps for Conducting a Scratch Test
•Start with Talc (Hardness 1):
•Begin by attempting to scratch the unknown
mineral with Talc (the softest mineral, hardness 1).
•If Talc scratches the unknown mineral, the unknown
mineral is softer than Talc (which is very unlikely).
•If the unknown mineral scratches Talc, it is harder
than 1.

45. PHYSICAL PROPERTIES - HARDNESS

46. PHYSICAL PROPERTIES - SPECIFIC GRAVITY
Specific Gravity (Density):
•Specific Gravity (Gs) is a measure of the density of a mineral compared to the
density of water.
•It is the ratio of the mineral’s density to the density of water at 4°C (which is 1
g/cm³).
•The concept of specific gravity provides a way to assess how heavy or light a
mineral is relative to its volume, which can be helpful for mineral identification.
•Specific gravity of minerals depends on their chemical composition and atomic
structure.
•Specific gravity of minerals is determined by using either Walker’s steel yard or
jolly’s spring.

47. PHYSICAL PROPERTIES - SPECIFIC GRAVITY
Specific Gravity (Density):
•Quartz with silicon dioxide has higher specific gravity of 2.7.
•Opal with Amorphous variety has lesser specific gravity2.2 .
•Amber as specific gravity nearly equal to water 1.
•Platiniridium is the heaviest specific gravity of 22.84.
•Rock forming minerals have specific gravity of 2.5 – 3.5.
•Ore forming minerals have specific gravity of over 3.5.

48. PHYSICAL PROPERTIES - SPECIFIC GRAVITY
Most sulfides are 4.5 to 6.0
Iron metal is ~8Lead is ~13
Gold and platinum are 19-22.

49. PHYSICAL PROPERTIES - DEGREE OF TRANSPARENCY
Degree of Transparency
•Degree of Transparency refers to how much light passes through a mineral.
•It is a key property used to describe and identify minerals based on how they interact
with light.
•Minerals can vary greatly in their transparency, from completely transparent (allowing
light to pass through) to opaque (not allowing any light to pass through).
•The resistance offered by materials to the passage of light through them.
•Transparency depends on chemical composition.
•Ore minerals exhibits opaque.
•Degree of transparency mainly depends on thickness.

50. PHYSICAL PROPERTIES - DEGREE OF TRANSPARENCY

51. PHYSICAL PROPERTIES - SPECIAL PROPERTIES
Magnetism
Magnetism refers to the ability of a mineral to attract or
repel other materials, particularly metals, due to the
presence of magnetic properties.
Some minerals are naturally magnetic, while others can be
influenced by external magnetic fields.
a.Strongly Magnetic (e.g.) Magnetite
b.Feebly Magnetic Slightly Magnetic (e.g.) Spinel
c.Non –Magnetic (e.g.) Quartz, Calcite

52. PHYSICAL PROPERTIES - SPECIAL PROPERTIES
Electricity(Pyro-electricity and Piezoelectricity):
Minerals can exhibit electrical properties when subjected to external conditions
like temperature changes or mechanical stress.
Two such properties are pyroelectricity and piezoelectricity, which are related to
the ability of some minerals to generate electric charge in response to specific
stimuli.
1.Pyro-electric: Minerals producing electric charge when heat applied, are called
Pyro-electric (e.g.) Quartz, Tourmaline.
2.Piezoelectricity: When Pressure applied certain minerals will glow (e.g.) fluorite.

53. PHYSICAL PROPERTIES - SPECIAL PROPERTIES
Fluorescence: When exposed to sun’s radiation (UV
light), certain minerals will glow (e.g.) Fluorite..
Phosphorescence: Some minerals continue to glow
even when bringing to the dark room after exposure
to sun’s radiation (e.g.) diamond.
Transparency: refers to a mineral's ability to transmit
light completely, allowing objects on the other side to
be seen clearly through it. Transparent minerals allow
light to pass through without significant scattering,
making them clear and easy to see through.
Translucency: refers to a mineral's partial transmission of
light, where light is transmitted but objects on the other
side cannot be seen clearly. Translucent minerals scatter
light, allowing some light to pass through but obscuring
detailed views of objects on the other side.
Opaque: refers to a mineral's inability to transmit light.
When a mineral is opaque, no light passes through it,
making it completely non-transparent. These minerals
block all light, preventing visibility of objects behind them.
Fusibility: A mineral's ability to melt or fuse when exposed
to high temperatures. This property is important in the
context of understanding a mineral's behavior when
subjected to heat, which is relevant in both natural
processes (such as volcanic activity) and human
applications (like metallurgy and material science).

54. CLASSIFICATION OF MINERALS
Minerals can be classified as:-
a.Silicate Minerals
b.Non-Silicate Minerals
c.Clay Minerals

55. CLASSIFICATION OF MINERALS - SILICATE MINERALS
Silicate Minerals:
The existence of a silicon tetrahedron makes a mineral as silicate mineral.
1.Felspar/ Feldspar group
2.Pyroxene group or pyroxenes.
3.Amphibole group or Amphiboles
4.Mica Group or Micas

56. CLASSIFICATION OF MINERALS - NON- SILICATE MINERALS
Non- Silicate minerals
These are minerals that do not contain silica tetrahedrons.

57. CLASSIFICATION OF MINERALS - CLAY MINERALS
Clay minerals:
These have properties that are of great importance to Geotechnical Engineers,
Some clays swell when wet and shrink when dry. Such clays can cause settlement in
foundation of structures and roads.
Gs of clay = 2.60 to 2.90.
Most of clay minerals are soft and exhibit plasticity when mixed with a limited
quantity of water.
Particle sizes (<0.002mm).
Examples: Kaolinite, Halloysite (amorphous), Montmorillonite, Beidellite,
Pyrophyllite, Allophane, Illite (hydro mica), chlorite, Bentonite clay, china clay
(Kaoline), Ball clay.

58. ROCK FORMING MINERALS
Rock forming Minerals
•The minerals which constitute the bulk of the rocks of the earth’s crust are called
the rock forming minerals.
•Civil engineers are more concerned with the rock forming minerals because they
need to know the properties of the rocks precisely, to enable them to consider
different rocks for their civil engineering uses, like: picking the rocks as good
foundations, or for using the rocks for making concrete aggregates, as building
stones, or road metal, or flooring, roofing, or decorative materials, etc.

59. ROCK FORMING MINERALS
Rock forming Minerals
Based on the nature and economic
importance all minerals are grouped
into Rock forming and Economic
minerals.
•Some economic minerals serve as a
source of extraction of valuable
metals and other become useful by
virtue of their physical properties.
•99% of the earth crust made up of
20- 25 rock forming minerals.

60. ROCK FORMING MINERALS
99.2% of the earth crust made of these
9 elements.
Oxygen and silicate together constitute
74.4%.
The rock forming minerals are mainly
silicates.
All precious and useful minerals such as
platinum, gold, silver etc., are together
represents only 0.436%. That’s why
economic minerals are scarce.
•The rock forming minerals are mainly
composed of silicates, oxides and
carbonates.
•Since silicate are the most common
rock forming minerals.

61. ROCK FORMING MINERALS GROUPS
Rock Forming Minerals Groups
•Feldspar
•Quartz
•Pyroxene
•Olivine
•Amphibole
•Mica
•Garnet
•Kyanite
•Chlorite
•Talc
•Calcite
•Bauxite