details about mineralogy and physical properties of minerals

1. Unit – 2
Mineralogy

2. A mineral:A mineral:
 is a naturally occurring inorganic crystallineis a naturally occurring inorganic crystalline
solidsolid
 has an ordered internal arrangement of atomshas an ordered internal arrangement of atoms
 has specific physical properties that are eitherhas specific physical properties that are either
fixed or that vary within some defined range.fixed or that vary within some defined range.
 has a definite chemical composition that mayhas a definite chemical composition that may
vary within specific limitsvary within specific limits

3. Types of minerals
Comman rock-forming minerals
(eg: feldspar,quartz,mica,kyanite etc)
Economic minerals
(eg:hematite,galena,chrimite,magnesite etc)

4. Importance of mineralogy
 As different rocks are used in different civil
constructions so as a civil engineer we must be know to
enable them to consider different rocks for different
construction purposes. Knowledge of properties like
strength, durability, and appearance of rocks can be
assessed by only with the knowledge of minerals that
forms rocks.

5. Different methods of study of minerals
 Study of physical properties
 Study of chemical properties
 Study of optical properties
 X-ray analysis

6. Study of Physical Properties of Minerals
 Form
 Colour
 Streak
 Luster
 Fracture
 Cleavage
 Hardness
 Specific gravity
 Degree of transparency
 Special Properties
 Other Properties

7. Importance of Physical properties of
minerals
Since every mineral possess different physical
properties so it is easy to know about the mineral by
knowing its physical properties.
From the civil engineering point of view it is very
important to know the physical properties of
minerals to use them in different constructions.

8. 1. Form:
Form is nothing but the physical
appearance of mineral. It I also called as
structure of the mineral.
Tabular form: mineral occurs in the
form of a flattened, square, rectangular
shape with uniform thickness
Lamellar form: mineral appears as thin
separable layers.
Bladed form: mineral appears as if
composed of thin, flat, parts as it is cutted
with blade.

9. Bladed form
 Granular form: mineral appears
in the form of densely packed
grains.
 Massive form: no definite
shape for minerals.
 Reni form: mineral appears
with no. of overlapped kidney-
shaped structures.
Granular form Massive form Reni form

10. 2. Colour: The colour of the any mineral is a
light dependent property. Sometimes it is because of
the presence of trace elements, sometimes due to
composition.
3. Streak: It is the colour of mineral powder.
Different minerals exhibit different streak most of
them exhibit white colour.
4. Lusture: It is the shining property of
mineral. It is dependent on;
•The refractive index
•The absorption capacity if light
•The nature of reflecting surface

11. Typical lustures of minerals
 Metallic: shines like a metal. Eg: galena
 Vitreous: shines like a glass. Eg: quartz
 Pearly: shines like a pearl. Eg: mica
 Silky: shines like a silk. Eg: gypsum
 Resinous: shines like a resin. Eg:opal
 Greasy: shines like a grease. Eg: graphite
 Dull: shine is almost absent. Eg: chalk.
 Adamantine: shines like a diamond. Eg:
diamond

12. 5. Fracture:
It is the nature of the randomly broken surface of a
mineral. It is less useful property of mineral because
most of the minerals shows same fracture.
Typical fractures of minerals
• Even : broken surface is smooth and flat. Eg: chalk
• Uneven: broken surface is irregular. Eg: most of the minerals.
• Hackly: broken surface is irregular with separable layers. Eg:
asbestos.
• Conchoidal: broken surface shows concentric rings. Eg: opal
• Sub-conchoidal; broken surface shows concentric rings with
less curvature. Eg:agate

13. chalk talc
biotite
opal

14. 6. Cleavage:
The definite
direction or
plane along
which a
mineral tends
to break is
called cleavage.

15. 7. Hardness:
It may be defined as the
resistance offered by
mineral to scratching.
Based upon the Moh’s
scale of hardness
minerals are arranged
according to their
hardness from 1 to 10.

16. 8.Specific gravity(density):
Density of a mineral is defined as mass per unit
volume of the mineral.
Density types of minerals
Low density - sp.gravity<2.5
Medium density - sp.gravity 2.5 to 3.5
High density - sp.gravity>3.5

17. 9. Degree of transparency:
The property of the mineral to pass light through it.
They may be classified as,
•Transparent
•Translucent
•opaque
10. Special properties: some minerals exhibit
special properties.

18. Advantages of study of minerals by
physical properties
 Study of mineral in field it self.
 Does not require any equipment
 No need of chemicals
 No loss or wastage of minerals
 Quickest method
 Cheapest, simplest and least tedious

19. Study of chemical composition
From definition minerals have its own distinctive
chemical composition. If the composition is known it is
easy to identify the mineral.
Study of optical properties
Making use of polarized light under crossed nicols, different optical
properties of the minerals like colour, refractive index, total
refraction etc. are studied.

20. Polarising microscope

21. X-ray analysis
It make use of the atomic structure of the mineral to
identify them. X-rays are similar to light waves but
have a much shorter wavelength.

22. Atomic structure of mineral by x-ray analysis
From: http://www.geology.fau.edu/course_info/fall02/gly4200/X-RAY.htm