2. 2
CONENTS
Practical
No.
Experiment Name Page
No.
01
MOHS SCALE OF
HARDNESS 03
02
STUDY OF MODELS OF FOLDS
AND FAULTS 08
03
International Geological
Symbols For Rock And
Minerals
15
04
Identification of rock
forming Minerals 19
3. 3
EXPERIMENT# 01
MOHS SCALE OF HARDNESS
Objective: To find Hardness of different Minerals
MOH'S SCALE OF HARDNESS
The Mohs' hardness scale was developed in 1822 by Frederich Mohs. This scale is a chart of
relative hardness of the various minerals (1 - softest to 10 - hardest). Since hardness
depends upon the crystallographic direction (ultimately on the strength of the bonds
between atoms in a crystal), there can be variations in hardness depending upon the
direction in which one measures this property. One of the most striking examples of this is
kyanite, which has a hardness of 5.5 parallel to the 1 direction ( c-axis), while it has a
hardness of 7.0 parallel to the 100 direction ( a-axis). Talc (1), the softest mineral on the
Mohs scale has a hardness greater than gypsum (2) in the direction that is perpendicular to
the cleavage. Diamonds (10) also show a variation in hardness (the octahedral faces are
harder than the cube faces). For further information see articles from the American
Mineralogist on microhardness, the Knoop tester, and diamonds.
Mohs' hardness is a measure of the relative hardness and resistance to scratching
between minerals. Other hardness scales rely on the ability to create an indentation into the
tested mineral (such as the Rockwell, Vickers, and Brinell hardness - these are used mainly
to determine hardness in metals and metal alloys). The scratch hardness is related to the
breaking of the chemical bonds in the material, creation of microfractures on the surface, or
displacing atoms (in metals) of the mineral. Generally, minerals with covalent bonds are the
hardest while minerals with ionic, metallic, or van der Waals bonding are much softer.
When doing the tests of the minerals it is necessary to determine which mineral was
scratched. The powder can be rubbed or blown off and surface scratches can usually be felt
by running the fingernail over the surface. One can also get a relative feel for the hardness
difference between two minerals. For instance quartz will be able to scratch calcite with
much greater ease than you can scratch calcite with fluorite. One must also use enough
force to create the scratch (if you don't use enough force even diamond will not be able to
scratch quartz - this is an area where practice is important). You also have to be careful to
test the material that you think you are testing and not some small inclusion in the sample.
This is where using a small hand lens can be very useful to determine if the test area is
homogenous.
7. 7
Calcite 3
Elmwood Mine,
Tennessee 8 cm.
(twinned)
Gypsum 2
Wyoming 12 cm.
Note "fishtail"
twin on left
Talc 1
Rope's Gold Mine,
Michigan (green) 4
cm. across talc
mass
8. 8
EXPERIMENT# 02
STUDY OF MODELS OF FOLDS AND FAULTS
FOLDS
“ FOld may be define as A curved or zig-zag structure shown by rock beds” OR
“The wavy undulation in the beds are called fold.
Types of Folds
(1) Symmetrical Fold:
A “symmetrical fold” is one where the two limbs dip at the same angle but in opposite
directions. In this case the axial plane is vertical and it passes through the crest or trough.
(Figure 1)
9. 9
(Figure 2)
(2) Asymmetrical Fold:
An “asymmetrical fold” is one where the two limbs dip at unequal angles in opposite
directions. On this case the axial plane is inclined and it not necessarily passes through the
crest line.
(Figure 1)
10. 10
(Figure 2)
(3) Overturned Fold:
It is an asymmetrical fold whose one limb is turned past the vertical. In this case the axial
plane is inclined and both the limbs dip in the same direction. In the overturned fold the
lower limb is turned upside down.
11. 11
(Figure 1)
(Figure 2)
(4) Recumbent Fold:
In “recumbent folds” , the folding is so intense that both the limbs become almost
horizontal. In this the axial plane also becomes nearly horizontal and the lower gets
overturned.
12. 12
(Figure 1)
(Figure 2)
FAULTS
In geology, a fault is a planar fracture or discontinuity in a volume of rock, across which
there has been significant displacement along the fractures as a result of earth movement.
Large faults within the Earth's crust result from the action of plate tectonic forces, with the
largest forming the boundaries between the plates, such as subduction zones or transform
faults. Energy release associated with rapid movement on active faults is the cause of
most earthquakes.
13. 13
A fault line is the surface trace of a fault, the line of intersection between the fault plane and
the Earth's surface
Since faults do not usually consist of a single, clean fracture, geologists use the term fault
zone when referring to the zone of complex deformation associated with the fault plane.
The two sides of a non-vertical fault are known as the hanging wall and footwall.
Classification of Fault
Normal fault:
A normal fault is one in which the hanging wall appears to have moved downward
relative to the foot wall. In this case the fault plane dips toward the down-throw side.
14. 14
1) Reverse fault:
A reverse fault is one in which the hanging wall appears to have moved upward
relative to the foot wall. In this case the plane dips toward the upthrow side. Normally
reverse faults have dips of the order of 45 degree or more.
19. 19
Experiment # 04
Identification of rock forming Minerals
Objective: To identify different rock forming minerals.
(1) Talc
Color: Light to dark green , brown , white , grey.
Streak: white to pearl black.
Specific Gravity: Its specific gravity is 2.58-2.83
Moh's Scale Of Hardness: 1
Use: Talc is used in many industries such as paper marking , plastic, paint, and coatings
rubber, food, electric cable, pharmaceuticals, cosmetics, ceramics etc.
(2)Mica
The mica group of sheet silicate (phyllosilicate) minerals includes several closely related
materials appears as sheety, shiny plated crystals.
Color: Shades of brown, Yellow, White, Black, Gray
20. 20
Streak: Gray
Specific Gravity: Its specific gravity is 2.76 – 3.2
Hardness: 2 – 2.5
Use: The principal use of ground mica is in gypsum wallboard joint compound, where it acts
as a filter and extender, provides a smoothly consistency, improves work ability and
prevents cracking.
(3)Calcite
Color: Colorless or white, also grey, green.
Hardness (Mohs): 3
Specific Gravity: 3
Steak: White.
Transparency: Transparent, Translucent.
Solubility: Soluble in dilute acids.
Use: Higher grade optical calcite was used in world War II for gun sights, specifically in bomb
sights and anti- aircrafts weaponry.
21. 21
(4) Malachite
Color: Bright green, yellow green, blackish green, commonly banded in masses ; green to
yellowish green in transmitted light.
Hardness (Mohs): 3.5 - 4
Steak: Light green
Specific Gravity: 3.6 – 4
Diaphaneity (Transparency): Transparent, Translucent
Use: Malachite is used in jewelry, ammunition, electrical circuits, electronic equipment,
appliances, automobiles, coins, etc. The ore is also used to build copper pipes. Primitive
people used malachite for making paint.
22. 22
(5) Gypsum
Gypsum is soft sulfate mineral composed of calcium sulfate dehydrate.
Color: Colorless to white, often tinged other hues due to impurities; colorless in transmitted
light.
Streak: White.
Hardness (Mohs): 2
Specific Gravity: 2.31-2.33
Diaphaneity: Transparent to translucent
Use: Gypsum uses include: manufacture of wallboard, cement, plaster of Paris, soil
conditioning, a hardening retarder in Portland cement. Varieties of gypsum known as "satin
spar" and "alabaster" are used for a variety of ornamental purposes, however their low
hardness limits their durability.
23. 23
(6) Hematite
Hematite, also spelled as hematite, is the mineral form of iron III oxide (Fe2O3), one of
several iron oxides.
Color: Steel-grey to black in crystals and massively crystalline ores, dull to bright "rust-red"
in in earthy, compact, fine-grained material.
Streak: Bright red to dark
red
Hardness (Mohs): 5.5 – 6.5
Diaphaneity (Transparency): Opaque
Specific Gravity: 5.26
Uses: It is used in rouge makeup and polish because of its red pigment. it is also used for
ore of iron for steel tools, vehicles, nails and bolts and bridges.
(7) Magnetite:
Color: Black
24. 24
Streak: Black
Hardness: 5.5 – 6.5 (harder than glass)
Transparency: Opaque
Specific Gravity : 4.9 - 5.2
Uses: Magnetite is used for many different things. Some of the things it is used for is to
make Magnets, Steel, Paints, Ink, Cosmetics and also to make Paper. Also used to make
some pieces of jewelry.
25. 25
(8) Bauxite:
Color: White, grey, yellow or brown.
Streak: White
Hardness: 1 - 3
Transparency: Opaque
Specific Gravity: 2.0 - 2.6
Uses: It is used as ore of Aluminium, refractory material,
abrasive material.
(9) Fluorite
Fluorite is found as a common gangue mineral in hydrothermal
veins, especially those containing lead and zinc minerals. It is also
found in some greisens, granites
Color: White, Blue, Green,Red, Yellow, Purple
Streak: White
26. 26
Hardness: 4
Transparency: Transparent
Uses: It is used as a making and for the preparation of
hydrofluoric acid.
(10) Dolomite:
Color: White, Pink, Gray, Greenish, Brown, Red
Hardness: 3.5-4
Streak: White
Transparency: Transparent to translucent on thin splinters
Specific Gravity: 2.8 - 3.0
Uses: It is used as a building and ornamental stone and in
manufacture of refractory bricks.
27. 27
(11) Aragonite:
Color: Color can be white or colorless or with usually subdued
shades of red, yellow, orange, brown, green and even blue.
Transparency: Crystals are transparent to translucent.
Specific Gravity is 2.95
Steak is white.
Hardness is 3.5-4
Uses: minor constituent of limestone which is used in cement and in
steel production, ornamental carvings and as mineral specimens.
