TEACHER NAME: SIR BILAL KHAN
MOHS SCALE OF
STUDY OF MODELS OF FOLDS
Symbols For Rock And
Identification of rock
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.
Zaire 1 cm. 14 carats
variety ruby, India 6 cm.
Mursinsk, Russia, 5cm across Seaman Museum specimen
variety amethyst, Guerro, Mexico 16 cm.
Orthoclase (white) on quartz, Baveno, Italy Orthoclase crystal is 3 cm tall. Seaman museum specimen.
Durango, Mexico. Crystal is 7.5 cm. tall. Seaman museum specimen.
Elmwood mine, Tennessee 2.5 cm. (note phantom)
Elmwood Mine, Tennessee 8 cm. (twinned)
Wyoming 12 cm. Note "fishtail" twin on left
Rope's Gold Mine, Michigan (green) 4 cm. across talc mass
STUDY OF MODELS OF FOLDS AND FAULTS
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.
(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
(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.
(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
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
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
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.
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.
International Geological Symbols For Rock
Experiment # 04
Identification of rock forming Minerals
Objective: To identify different rock forming minerals.
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.
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
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.
Color: Colorless or white, also grey, green.
Hardness (Mohs): 3
Specific Gravity: 3
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.
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.
Gypsum is soft sulfate mineral composed of ca