Unit-I
MINERALOGY

Crystallography
 When mineral solidifies and grow without interference under favorable conditions they will usually adopt smooth, angular and symmetrical shapes. Known as crystal.
 When the solid substances formed are in disorderly manner do not acquire fixed shapes known as amorphous substance.
 Transformation of amorphous material to crystalline material known as devitrification.
Amorphousglobalizesmargarineslongulitestrichitesscopulites
microlites
Microlites are crystalline minerals with definite properties, enabling
Indentification of minerals.


Crystal systems:
Six general groups
1. Isometric(cubic)system ex: diamond
2. Tetragonal system
3. Hexagonal system
4. Ortho-rhombic system
5. Monocline system
6. Triclinic system
These groups are called crystal systems and the overall study of crystals is crystallography.

Isometric system:
It is the best possible perfect atomic arrangement.
Lowest order of symmetry occurs in the 6th system.
(ie)Tricline




























































Important terminology relating to crystallography

1.Crystal facesThe crystals are bounded by flat surface known as faces

2.Edge.
The line of inter-section formed by any two adjacent faces in a crystal is edge.

3.Solid angle:The points of inter section formed by three or more adjacent faces in a crystal is solid angle

4.Distortion:
The crystals with different size& shapes
(ie)geometrical irregularity called as Distortion:

5. Interfacial angle:
The angle formed in between the normal of adjacent crystal faces known as interfacial angle.

6. Simple form and combination form:
If a crystal is bounded by all similar or like faces is simple form
It is bounded by dissimilar or unlike face is combination form

7. Crytalographic axes:
It is an imaginary line extending thought the centre of crystal

8. Symmetxy:
The faces, edges and solid angles crystal occur with some regularity or plane of symmetry, axes of symmetry centre of symmetry.

9. Twinning:
 In a homogenous mineral aggregate various mineral crystal are usually found to occur in parallel position known as parallel growth.
 Two halves of the crystal, thus related may show some of the crystallographic direction arrested in oblique disposition known as Twinning
 One half of the twins appear to form the mirror Image of the other half known as plane of Twinning
 Due to rotation of one half through 180˚ about a definite axis of rotation called as axis of Twinning
 The two trained halves of crystals ordinarily lie side by side and are mutual contact along a plane called as composite plane.










Three type:
Simple Twinning
The two halves of the crystal for mining mirror image remain in contact along the composite plane


b)Repeated Twinning or polysynthetic:
Is made up of three or more parts, formed due to several repetitions of same kind.

C)Penetration twinning :
The two twinned portions are found to have inter grown & cannot be separated from each other.











Classification of crystal
1. Symmetry characters
2. Axial characters.

I. Symmetry characters.
a) Centre of symmetry:
The central point of a crystal about which similar parts are arranged in opposite directions at exactly equal distance in corresponding positions.

b)Planes of symmetry:
An imaginary meridian plane that divides a crystal into two mirror image halves.

c)Axes of symmetry:
An imaginary line in between the middle points of opposite and similar parts through the center about which when the crystal is rotated in a complete rotation of 360˚.

II Axial characters:
Crystallographic axes are a set of 3 or 4 reference axes the axial characters
1.Number
The actual number of axes 3 or 4

2.Length:
The relative length of the axes
3.Intersection:
The angular relationship of the crystallographic axes at the center.
Refer the diagram

Physical properties of Minerals:
Def:
An inorganic element or compound in its natural state is called a mineral.
• It must occur naturally as an inorganic substance
• Its composition should represent a definite chemical formula
• It must have an orderly internal structure.
• Its physical properties must be fixed.
The physical properties of minerals depend upon several factors like
a) Degree of aggregation a whole formed
b)Degree of cohesion
c) Senses, light, magnetism, heat, electricity
The various physical properties
1. External appearance & internal structure
2. cleavage
3. Fracture
4. Hardness
5. specific gravity
6. Tenacity
7. Colour
8. Steak
9. Lustre
10. Transparency
11. Fluorescence
12. Phosphorescence
13. Other miscellaneous properties

1. External appearance and internal structure
Most mineral posses certain definite geometric shape bounded by smooth planes in the form of well defined solid called crystals.
• Three dimensional arrangements called the internal structure of mineral.
• Internal structure controls the external shape of the crystal

2. Cleavage

Crystallized minerals have a tendency to break more readily in certain direction than in others producing more or less a smooth surface
S.NO TYPES OF CLEAVAGE REPRESENTED BY EXAMPLE
1 Basal cleavage There is one set of cleavage. Muscovite
2 Prismatic cleavage There are two sets of cleavage. Hornblende
3 Cubic cleavage There are three sets of cleavage at right angle to each other Galena
4 Rhombohedral cleavage There are three sets of cleavage other than right angle Calcite
5 Octahedral cleavage There are four sets of cleavage. Magnetite
Which reflects light .The tendency of a mineral to bream along the planes of the laciest fracture is cleavage. The plane along which the crystal breaks are called the cleavage planes.
Different types of cleavages


S.NO TYPES OF FRACTURE REPRESENTED BY EXAMPLE
1 Even fracture When the broken surface of a mineral are smooth Chert
2 Uneven fracture When the mineral breaks with very rough and coarse surface Chromite
3 Conchoidal fracture When the mineral breaks with curved surfaces. Quartz
4 Hackly fracture When the mineral breaks with irregular surface having sharp edges Copper
5 Earthy fracture When the broken surface is soft and smooth chalk

3.Fracture:
The fracture is defined as the appearance of its broken surface, when the mineral is hammered and broken.
Different types of fractures

4. Hardness:

It is defined as the resistance which the mineral offers to scratching.
MOH’S SCALE OF HARDNESS

S.NO MINERAL HARDNESS(H)
1 Talc 1
2 Gypsum 2
3 Calcite 3
4 Fluorite 4
5 Apatite 5
6 Feldspar 6
7 Quartz 7
8 Topaz 8
9 Corundum 9
10 Diamond 10
11 Knife 6.5
12 Glass plate 5.5
13 Brass 3
14 Finger nail 2.5

5. Specific gravity:
Sp.G= wa
Wa-ww
Wa=weight of the mineral in air
Ww=weight of the mineral in water
Sp.gravity varies between 2 to 7
Specific gravity can be tested by the following methods
1. Jolly’s balance
2. Beam balance
3. Pyconometer
PYCONOMETER MEYHOD
It is used to determine the specific gravity of fine sediments or mineral samples in powdered form. Pyconometer is a small glass bottle with a stopper. Here
W1 = weight of the empty bottle
W2 = Weight of the vessel containing powdered mineral
W3 = Weight of the vessel containing powdered mineral + little amount
Of water
W4 = Weight of the vessel containing water.
Specific gravity = (W2 -W1 ) *d

(W4 – W1) – (W3 – W2)
d = specific gravity of water




SPECIFIC GRAVITIES OF IMPORTANT MINERALS

S.NO MINERAL SPECIFIC GRAVITY
1 Talc 2.70-2.90
2 Gypsum 2.32
3 Calcite 2.72-2.90
4 Mica 2.7-3.1
5 Illite 2.84
6 Hematite 4.9-5.3
7 Quartz 2.65
8 Kaolinite 2.61
9 Limonite 3.8
10 Hornblende 3.2-3.5

6. Tenacity:
It defines the characters like lirttleness, sectility, mallealuility, flexibility & elasticity.
DIFFERENT TYPE OF TENACITIES OF MINERALS
S.NO TYPE OF TENACITY REPRESENTED BY EXAMPLE
1 Sectile When the mineral can be cut with a knife Talc
2 Malleable When a mineral flattens into sheet, when hammered Silver
3 Brittle When a mineral crumbles to grain or powder, when hammered Quartz
4 Flexible When a mineral can be easily bent Chlorite
5 Elastic When a flexible mineral on being bent, regains its original position, as bending force is removed muscovite


7. Colour:
The colour is not a very realizable source of identity ying a mineral as it can be affected by impurities present in the mineral sample
Pyrite brass yellow
Caluite-white
Muscovite-colourless
Sulphur-yellow


COLOURS OF THE MINERAL
S.NO MINERAL COLOUR
1 Pyrite Brass-yellow
2 Hornblende Greenish-black
3 Biotite Brownish-black
4 Muscovite Colourless
5 Sulphur Yellow
6 Calcite white

8. Streak:
The streak of the mineral is the colour of its powder

COLOUR-STREK COMBINATION
S.NO MINERAL CHARACTERISTIC COLOUR-STREAK COMBINATION
COLOUR STREAK
1 Hematite Black Cherry-red
2 Chromite Greenish-black Greenish-brown
3 Pyrite Brass-yellow black
9. Lustre
The shine of a mineral is called lustre.
DIFFERENT TYPES OF LUSTRES
S.NO TYPE OF LUSTRE REPRESENTED BY EXAMPLE
1 Vitreous lustre A mineral having a glassy shine Quartz
2 Pearly lustre A mineral having a pearly shine Muscovite
3 Metallic lustre A mineral having a metallic shine Magnetite
4 Silky lustre A mineral with a silky shine Asbestos
5 Resinous lustre A mineral with a greasy shine Talc
6 Admantine lustre A mineral having a diamond like shine Diamond






10. Transparency:
It is defined as its capability to pass light through it
DIFFERENT TYPES OF TRANSPARENCIES
S.NO TPPE OF TRANSPARENCY REPRESENTED BY EXAMPLES
1 Transparent Mineral which allows the light to pass fully Quartz
(colourless varieties)
2 Semi transparent When the light is passed partially Quartz
(silky milk varieties)
3 Translucent a mineral which allow only some diffused light to pass Quartz
(milky white varieties)
4 Opaque A mineral which does not pass any light orthoclase

11. Fluorescence:
It is the property of a mineral due to which it may emit light when exposed to radiations like x ray
Ex: floors par
12. Phosphorescence:
Mineral may emit light after it has been exposed to certain radiation or subjected to heating or rubbing

Rock forming minerals
(I)FELSPAR FAMILY
PLAGIOCLASE FELSPAR
S.NO PHYSICAL PROPERTIES EXPLANATION
1 Chemical composition (Na.AL.Si3O8) and (Ca AL2,SI2O8)

2 Crystal system Triclinic crystal system
3 Colour White to grey
4 Cleavage Double cleavage at about 90 degree
5 Hardness 6
6 Specific gravity 2.6
7 Tenacity -
8 Fracture Uneven
9 Streak white
10 Lustre pearly
11 Transparency -
12 Present in Igneous rock


FELSPAR FAMILY
OTHOCLASE FELSPAR
S.NO PHYSICAL PROPERTIES EXPLANATION
1 Chemical composition (K AL Si3O8)

2 Crystal system monoclinic crystal system
3 Colour Pink to flesh co lour
4 Cleavage Perfect Double cleavage at about 90 degree
5 Hardness 6
6 Specific gravity 2.56-2.58
7 Tenacity -
8 Fracture Uneven
9 Streak White
10 Lustre vitreous
11 Transparency
12 Present in Igneous rock

FELSPAR FAMILY
MICROLINE FELSPAR
S.NO PHYSICAL PROPERTIES EXPLANATION
1 Chemical composition (Na.AL.Si3O8) and (Ca AL2,SI2O8)

2 Crystal system Triclinic crystal system
3 Colour White to grey
4 Cleavage Double cleavage at about 90 degree
5 Hardness 6
6 Specific gravity 2.6
7 Tenacity -
8 Fracture Uneven
9 Streak White
10 Lustre vitreous
11 Transparency -
12 Present in Igneous rock

(II)QUARTZ FAMILY
S.NO PHYSICAL PROPERTIES EXPLANATION
1 Chemical composition (SiO2)
2 Crystal system Hexagonal crystal system
3 Colour Black,pink,yellow
4 Cleavage No
5 Hardness 7
6 Specific gravity 2.65
7 Tenacity No
8 Fracture Conchoidal fracture
9 Streak No
10 Lustre vitreous
11 Transparency No
12 Present in Igneous rock
13 Uses Manufacturing glass, pottery, optical instruments etc.

(III)AUGITE
S.NO PHYSICAL PROPERTIES EXPLANATION
1 Chemical composition [(Ca,Na)(Mg,FeII,FeIII,AL)(Si,AL)2O6]
2 Crystal system Monoclinic crystal system
3 Colour Black-dark green
4 Cleavage Two dimensional distinct prismatic cleavage at about 90 degree
5 Hardness 5 to 6
6 Specific gravity 3.2-3.5
7 Tenacity -
8 Fracture Uneven
9 Streak Grayish white
10 Lustre vitreous
11 Transparency -
12 Present in Igneous rock, metamorphic rock
13 Uses Making gem stones

(IV)HORNBLENDE
S.NO PHYSICAL PROPERTIES EXPLANATION
1 Chemical composition [Ca2Na (Mg,FeII) (AL,FeIII,Ti) (AL.Si)8O22 (O,OH)2]
2 Crystal system Monoclinic crystal system
3 Colour Black-dark green
4 Cleavage Directional distinct cleavage at about 120 degree
5 Hardness 5
6 Specific gravity 2.9-3.4
7 Tenacity -
8 Fracture Uneven
9 Streak Greenish white
10 Lustre vitreous
11 Transparency -
12 Present in Acidic Igneous rock
13 Uses Manufacturing cement

(V)MUSCOVITE OR POTAS MICA

S.NO PHYSICAL PROPERTIES EXPLANATION
1 Chemical composition [K AL2(AL Si3 O10) (OH)2]
2 Crystal system Monoclinic crystal system
3 Colour White
4 Cleavage perfect cleavage at about 90 degree
5 Hardness 2 to 2.5
6 Specific gravity 2.7-2.9
7 Tenacity -
8 Fracture Even
9 Streak No
10 Lustre Vitreous to pearly
11 Transparency -
12 Present in Igneous rock, metamorphic rock
13 Uses Used as an insulating material in electric instruments.

(VI)GARNET

S.NO PHYSICAL PROPERTIES EXPLANATION
1 Chemical composition [Fe3AL2(SiO3)4]
2 Crystal system Isometric crystal system
3 Colour Purple or deep red to black
4 Cleavage No
5 Hardness 6.7 – 7.5
6 Specific gravity 4.0 – 4.3
7 Tenacity -
8 Fracture Uneven and conchoidal or subconchoidal
9 Streak No
10 Lustre Vitreous
11 Transparency Transparent to opaque
12 Present in Metamorphic rock
13 Uses Manufacture of “garnet paper” , used as an abrasive, and used as ornamental stone

(VII)CALCITE

S.NO PHYSICAL PROPERTIES EXPLANATION
1 Chemical composition (CaCO3)
2 Crystal system Hexagonal crystal system, may occur in prismatic crystal system
3 Colour White or colourless
4 Cleavage Perfect typical rhombohedral cleavage
5 Hardness 2.5 to 3
6 Specific gravity 2.7
7 Tenacity -
8 Fracture Conchoidal fracture
9 Streak No
10 Lustre Vitreous to earthy
11 Transparency Transparent to opaque
12 Present in Metamorphic rock
13 Appearances Tabular or granular , fibrous
13 Uses Used for making prisms used in optical instruments, manufacturing cement, bleaching powder, used as building stone and as a road metal.
(VIII)BIOTITE MICA
S.NO PHYSICAL PROPERTIES EXPLANATION
1 Chemical composition H2K(MgFe)3AL(SIO4)9
2 Crystal system Foliated commonly flaky
3 Colour Brownish black
4 Cleavage One set of perfect basal cleavage
5 Hardness 2 to 2.5
6 Specific gravity 2.9-3.1
7 Tenacity -
8 Fracture Uneven
9 Streak Pale brown
10 Lustre pearl
11 Transparency -
12 Present in Acidic Igneous rock
13 Uses Manufacturing cement


Clay mineral
Clay minerals are mainly formed due to alterations or decomposition
( break down) of the pre existing silicate minerals.
Ex: Kaolinite clay mineral is formed by the break down of feldspar (silicate mineral) by the action of water & Co2.Clay are also formed by hydrothermal activity.
Varieties of clay minerals and their chemical compositions
• All the clay minerals are basically hydrous silicates.
• Some may have little potassium magnesium, sodium, Iron etc.
Chemical composition:
1.Kaolinite=Al4Si4O10(OH)8
2.Halloysite=Al4Si4O10(OH)8.4H2O
3.Montmorillonite= Al4Si8O20(OH)4.H2O
4.Beidellite= Al4(Al Si)8O20(OH)2
5.Pyrophyllite=Al2Si4O10(OH)2
6.Allophane=Al4Si4O10(OH)8
7.I llite=KAl4 Alsi7 O20(OH)4
8.Chlovite=(Mg,Fe)5(Al Al Si3)O10(OH)8

Atomic structure in clay minerals
 The clay minerals do possess sheet structure & crystallize under the monoclinic crystal system
 The basic structural units of most of the clay minerals consists of silica tetrahedron
 Various clay mineral are formed by stacking of combination of the basic sheet structures with different forms of loading between the combined sheets
 Before joining the basic units (ie.silica &alumina) occurs to form a clay mineral, silica & aluminum may sometime the partially replaced by other elements such as magnesium, potassium, Iron etc & this reaction known as isomorphism substitution.
 In kaolinite clay mineral, limited isomorphism substitution take place & the combined silica alumina sheets are held together fairly tightly by (hydrogen)(H)bonding.
 A kaolinite particle consists of 100 stacks of silica & alumina sheet
 In an Illite clay mineral, one alumina sheet is combined with two silica sheet.
 In the alumina sheet, aluminum is partially substituted by magnesium & iron. While in silica sheet, there occurs a partial substitution of silicon by ammonium.
 The combined sheet fairly became weak bond due to non-exchangeability potassium irons held between them.
 In the montmorillonite clay the basic structure is some as illite liest alumina sheet is partial substitution of aluminum by magnesium. The spare between the combined sheets is occupied by water.
 Swelling of montmorillonite occurs.
 The surfaces of clay particles carry residual negative charges. The negative charges result in cat ions present in the water in the void space being attracted to the particles .If nature of water changes the cat ion is replaced by other cat ions known as cat ion exchange.
 Different structures are formed on the basic of orientation of particles.
 Clay structure forming due to interaction between single clay(ie)face to face is dispersed structure and edge to face or edge to edge is flocculated structure.
 This is due to force to attraction (i.e.) vander Waals force.
 When the interaction occurs between the various clay mineral particles complex structure take place.




Physical properties of clay minerals
Common clay mineral in use
(i)Bentonite clay
It is formed by the alteration of volcanic ash. It is mainly composed montmorillonite and beidellite.
Bentonite clay is generally of two types
(a) Sodium bentonite
It is mainly of swelling type
(b) Calcium bentonite
It does not depend upon swelling type.
Uses:
a) Drilling wells
b) Decolorized of oils and fats
c) Foundry sand
d) Tooth paste & cosmetic preparation
e) Brining agent in palletizing iron are fines
(ii)China clay(Kaoline)
It is a variety of Kaoline clay and it does not swell with the addition of water. It is white in colour.
Uses:
1. In manufacture of crockery
2. Industries producing textiles papers, rubber, paints, cosmetic etc
(iii)Ball clay:
 It is large in silica content
 It contain small quantity of montmorillonite mineral
 It has a high plasticity
Uses :
Used in different ceramics
(iv)Fire clay:
 It has impurities of oxides of calcium, iron titanium, magnesium& alkalis
 It is white,grey,or black in colour
 It possesses good plasticity
Uses :
Used in the manufacture of acid refractory bricks
(v)Fuller’s earth:
a) It is greenish brown, bluish or grayish clay which becomes powdery in water, but does not become pasty.
b) It is mainly composed of montmorillonite clay.
Uses:
 Used in refining oil
 Used for cleaning fabrics
(vi)Lithomarge:
It is white, yellowish or reddish clay made up of kaolinite & halloysite clay.
It adheres strongly to the tong and has a greasy feel
Occurrence of clay minerals:
 Clay being the products of weathering remain in same place formed as residua clay
 Sometimes undergoes transport by genocidal agencies like river, wind etc.and get deposited as beds in seas, lakes.
 Fire clay is often found beneath the coal seams.

Economic Mineral Deposits
ORE MINERAL
Natural occurring are mineral is defined as a mineral which contains a metallic element in a quantity that can be exploited and extracted for use at an economical cost.
 Clay is rich in aluminum but cannot be extracted from it at an economical cost
 Bauxite, an oxide of aluminum is an ore of aluminum can be extracted from bauxite by electrolytic refining.
Ore deposit
Natural concentration of an ore mineral in a massive rock is defined ad are deposit.
A small patch or layer of bauxite, say one meter thick & a kilometer long will not make ore deposit, should need million of tons to quality as an ore deposit.
Oxygen of ore deposits:
 Mineral deposits occur independently forming layers and bodies of different shape extending for many kilometers in area extent & up to may meters in depth
 In other case the ore deposits may be present in an enclosing rock called as country rock or host rock
 The host rock is removed in the first stage of mining. The minerals are then separated at second stages of exploitation. It is divided into two groups
1.Syngenetic deposits:
It is formed by enclosing the rocks simultaneously



2.Epigenetic deposits:
It is formed by subsequent (coming after something at time) to the formation of the host rock.
Igneous deposits
It is formed by crystallization of very hot field of magmatic in different environments.
1. Magmatic deposits:
During the crystallization of a magmatic melt, many minerals of economic value formed depending on the original composition of the melt. These minerals get concentrated towards the bottom or margins.
It is formed in the following forms.









2. Disseminations:
In magma tic disseminations, the economic minerals are dispersed at random in a cooled igneous body.
Ex: diamond
3.Magmatic Injections
These are thin, lenticular or slightly latuloar bodies of magma tic minerals that appear is intruded or injected into the host rocks.
When the magma rise up with sufficient hydrostatic force it may intrude into available fissures and fractures in the surrounding rocks where eventually it may cool down injection deposits may result both as early and late stages of crystallization.



Hydrothermal deposit:
It is formed by coaling of gaseous and liquid solution in cavities, fissures or pores space of the rock.
The there essential conditions for the formation of hydrothermal deposits are
1. Highly active & enriched fluids
2. Suitable pathways
3. Suitable physical chemical environment
Hydrothermal deposits occur in a variety of shapes and sized.
1.Venis :It is a narrow, elongated or lenticular bodies of economic minerals occurring within a host rock.
a).Fissure-venins
It is defined as mineral bodies of elongated or tabular shape deposited in pre-existing fissure. It is parallel or fan shaped in pattern.

B)Ladder veins:
It is found in igneous rocks consist of tranisverse, roughly regularly spaced fractures and give a ladder like impression in vertical section.

c) Gash-veins:
It is narrow, sloping & thick bodies deposited in the cracks of the host rock.


2.Stock works:
It is found within a limited space.Mining,recoves the entire rock body containing the stock work.












3. Cavity filling
The ore get deposited in well defined open spaces within a rock

4. Saddle Reef
The ore get deposited in folded rocks. (Along the crest of anticlines and troughs of synclines)













Sedimentary deposits:
Important deposits of ores of iron, copper, gold, phosphates & coal are of sedimentary orgin.
A) Weathering:
Atmospheric gases and water vapour are incessantly reacting with surface rocks of suitable composition where by the get decomposed & altered. This is called as weathering of rocks.
Most of the useless materials from the looses mantle is leached away or removed by subsurface waters leaving behind residual material known as residual deposits.
Sedimentary genesis
1. Erosion
2. Transport by wind water
3. Deposit
Metamorphic deposits
It is a natural process of change brought out in rocks of all types subjected to changed conditions of temperature pressure and chemically active fluids
Mineral resources of India
India –Iron aluminum, magnesium titanium.


Coal
Chemical Composition of Coal
Coal, as even a layman knows, is a very important fuel, used in homes as well as in furnaces in industries and power plants. It, infact, forms the backbone of all schemes aimed at the industrial progress of a country; and hence it is of utmost economic importance to a community.
Coal is, infact, formed by the transformation of burried vegetation matter into the carbonaceous product, over a period of time. In composition, therefore, it consists of carbon with moisture, volatile matter, and some mineral residuals*.
The relative proportion of fixed (or pure) carbon, in relation to volatile matter and moisture, decides the quality of coal. The greater the percentage of fixed carbon present in a coal sample, the better will be its quality.

Origin of Coal
Coal, as started earlier, is formed by the transformation of vegetation matter into the carbonaceous product. Formation of large coal deposits, therefore, requires large accumulation of vegetation matter (plants). The vegetation matter may either get burried at the place of its growth, giving rise to insitu – deposits of coal; or the vegetation matter may be transported by streams, and deposited along with other sediments at suitable places, which on transformation, give rise to drift deposits of coal. The Indian coal deposits are of drift type.
The initial decomposition of the burried accumulate vegetation matter into carbonaceous product, takes place through several bio – chemical processes. With this initial decomposition, starts the process of transformation into coal. The effect of heat and pressure due to further consolidation results in the expulsion of moisture and volatile constituents, giving rise to coal of higher grades. As this process of dynamochemical transformation continues, improved varieties of coal get produced.

Varieties of Coal
Depending upon the amount of biochemical decomposition and dynamo – chemical transformation undergone, a number of varieties or types of coal have been recognised. These include the following four types of coal :
1. Peat
2. Lignite;
3. Bituminous coal; and
4. Anthracite
These four types are briefly described below :
Peat
Peat indicates the first stage in the transformation of vegetation matter into coal. Infact, it represents only partly altered or carbonised vegetation matter. Obviously, vegetation matter such as, read’s and tree’s residulas, can be seen in this coal by naked eyes. Chemically, it contains a large percentage of moisture; and other ingradients include carbon, sulphur, nitrogen and hydrogen. Peat formations can be seen going on in ponds, lakes, and bogs.
Two types of peat are commonly recognized; i.e. Bog peat, which is evolved out of lower vegetation like mosses; and (ii) Mountain peat, which is the decomposed form of higher type of vegetation, such as trees, etc., and commonly forms in the lower altitudes of mountains.
Peat is commonly used as fertiliser, or as a fuel in dried forms.
(2) Lignite. Lignite indicates, the next stage after peat, in the process of coal formation. The vegetative matter in lignite is thus, more decomposed and carbonised than in peat.
Lignite is characteristically soft mass, brownish in colour, and earthy in appearance. It is also commonly known as brown coal. In composition, it contains carbon up to about 40% moisture upto about 40% (and always less than 70%) and volatile matter up to about 20%; although these percentages can very considerably. Its heat value, may also accordingly vary considerably, and may range from say 7000 to 11500kJ**.
Lignite is extensively used as a fuel for domestic purposes. Superior varieties are used in thermal plants and steam engines, etc.
(3) Bituminous Coal. This is the real coal formed from lignite; although, it represents the poorest variety of coal, and is known as soft coal or coking coal.
Bituminous coal is a black coloured, brittle substance, in which plant residuals are not visible. In chemical composition, bituminous* coals show considerable variation, with carbon from 40 to 90%, moisture from 5 to 20% and volatile constituents from 10 to 45%. It heat value varies from 9500 to 16,000kJ**.
The bituminous coal shows a typically banded appearances, and the bands are of dull and bright lustre, with an alternating arrangement. These bands are further classified into four types, i.e. vitrain, clarain; durain; and fusain. The vitrain variety is characterised by a glassy lustre, conchoidal fracture and small thickness; whereas, clarain bands are less brittle, less vitrous and more thick, and also richest in recognisable plant matter. These often show fine laminations. Duralin, the dull coal, is lustreless in appearance and shows rough fracture. Fusain shows woody fibrous tissues when seen under a microscope, but is apparently soft, granular and friable in nature.
Bituminous coal, or the ordinary coal of market, is widely used as a domestic fuel, and in metallurgy as metallurgical coal.
Its grey to black coloured variety, exceptionally rich in resins and spores of plants (which are believed to have been deposited by wind in sub – aqueous conditions), is called cannel coal, and it is quite rich in volatile matter. Another similar variety, which appears like cannel coal, but on microscopic examination shows a higher percentage of algal remains and volatile matter, is called bog – head coal.
(4) Anthracite. Anthracite is the highest quality coal, formed by metamorphism* of bituminous varieties. It is richest in fixed carbon (92 – 98%) and poorest in volatile matter (1 – 5%), and hence possess no caking power. They burn without smoke and donot soften, with heat value ranging from 14500 to 16000kJ. Anthracite is used mostly for raising steam, and also for metallurgy works.
Mode of occurrence of Coal
Coal is a sedimentary deposit, and, therefore generally occurs as thick and thin beds of variable extent, like all other sedimentary formation. Lignite may sometimes occur as small bands or patches. Peat occurs in bogs, ponds and lakes.

Indian Occurrence of Coal
Ordinary Bituminous coal widely occurs in India (as thick and extensive seams or beds) in the lower gondwana rocks at Jharia**, Bokaro, Girdih (all in Bihar State); Korea, Ballarpur, Umaria, Sohagpur (all in Madhya Pradesh), Talchir (in Orissa); Raniganj (in West Bengal); and Kothagudam, Tandur, Signgareni, etc. (in Andhra Pradesh). So much so that about 98% of the coal annually produced in India, comes from these deposits of bituminous coal.
It has been estimated that India contains about 40,000 million tonnes of proved reserves of bituminous coal, and an additional 80,000 million tonnes of inferred reserves, thus totalling 1,20,000 million tonnes of coal potential. This estimate is based on seams of atleast 1.2 m thick (i.e. min. thickness reqd. for mining) existing upto a depth of 600m.
Lignite mostly occurs in the Teritary rocks at Neyveli (in Tamil Nadu), and in some very small quantities in the deposits at Palana (Rajasthan); Makum and Nazira (Assum); Jangalgali and Nichochama (Jammu and Kashmir); etc. So much so that about 3400 million tonnes of Lignite occurs in Neyveli, out of its total estimated quantity of 3530 million tonnes.
Although the overall position of coal reserves of India appears to be quite rosy, but actually it is not so. Because, in contrast to this rosy quantitative position, the qualitative position is far from satisfactory. Indian coals are not of very good quality. The cooking coal, with low ash content, known as metallurgical coal, and so essential for the industrial progress, is of a very limited occurrence; the reserves being only of the order of 1525 million tonnes.
The annual output of coal in India is about 25 million tonnes; with Jharia fields producing about 40% of this output.

Petroleum
Chemical Composition of Petroleum
Petroleum, as we all know, is an oil that is found entrapped within the rocks of the surface of the Earth (generally found in deserts or deep into the oceans). In chemical composition, it is a complex mixture of highly inflammable hydrocarbons (with general formula CnH2n – 6)*, with minor quantities of other compounds like sulphur, nirogen, oxygen traces of metals like vanadium, nickle, etc., present in it. Because of its black colour and great economic value, it is also popularly known as black gold.

Origin of Petroleum
The origin of petroleum has been a matter of controversy. There are two entirely diverse theories, viz. the inorganic theory and the organic theory.
In the inorganic theory, the inorganic materials like iron carbides, alkali metals, water, and carbon dioxide are thought to be responsible for its formation. However, this theory finds little support because the evidence is more in favour of the other view.
According to the organic theory, the organic matter, such as remains of plants and animals, are held responsible for the formation of petroleum. These organic products (micro – organisms) are thought to have been accumulated in enormous amounts at suitable places, which are free from oxygen, such as gulfs and other such places with least flow of water. The bio – chemical processes do result in the transformation of the organic matter into hydrocarbons forming petroleum. This theory is convincing, as it is supported by the fact that oil, though in small quantities, occurs in association with coals.


Migration and Accumulation of Petroleum
Petroleum oil is a migrating mineral. It does not stay for long at the place of its original formation. Being lighter than water, it easily floats in water, and hence moving water easily carry it along with itself. The pressure due to the overlying sediments may also result in the squeezing out of the petroleum formed, forcing it to found its way along weak and permeable zones. Obviously thus, petroleum oil keeps on migrating along fissures, fault planes and permeable beds, untill it is trapped, and its further movement gets checked, resulting in the formation of an oil deposit. Further supply from behind, if available, enlarges the deposit. In view of this migration, a search for oil requires a search for oil traps.

Extraction of Petroleum and its products
Crude petroleum, which is obtained from the oil field, is taken to a refinery. This is a place where the crude oil is refined and turned into its various products like bitumen, diesle oil, kerosene oil, petrol, etc. Refineries are usually built in countries, where the oil is actually used.
The crude oil is made up of many liquids mixed together. These liquids turn into vapour and condense at different temperatures. In a refinery, the crude oil is heated in pipes in a furnance. The liquids (present in the crude oil) turn into vapour, and rise in the pipes in a tall steel tower. As the vapour rise slowly in the tower, they cool down and get liquidfied, at different heights, as shown in Fig. 13.6. As the different liquids get condense at different heights in the tower, each kind of oil is separated out at different heights in different compartments. Each separated oil is then further improved in other parts of the Refinery. Heavy oils are infact separated out from the bottom and the lighter ones from the top. In this way, we get bitumen, diesel, kerosene, petrol, etc. Waste of crude oil is also taken to various parts of the refinery, where plastics, fertilizers, paints, rubber, wax, drugs, etc. are manufactured out of it.


Petroleum Production in India
India produces about 6% of the total petroleum production of the world. The deposits of petroleum and gas in India, are generally found in the Tertiary rocks in Assam. The important Assam oil fields are Digboi, Makum, Badarpur and Nahorkatiya. In addition to these on – shore oil depoisits, Cambay and Ankleshwar in Gujarat are also meeting part of our supplies. From a mere 100 tonnes of oil produced per day in 1961, we have gone to a production of about 40,000 tonnes per day on on – shore side.
Similarly, off – shore oil production has gone up from a mere 2 million tonnes per annum in 1977 (when this was started in Bombay High) to about 12 million tonners per annum at present. The work of extraction of petroleum in India is done by ONGC (Oil and Natural Gas Commission).
Part - A
1. Write the significant Engineering properties of granite?
2. Write the hardness of calcite and apatite minerals?
3. What are the diagnostic characteristics of Kaolinite and illite clay minerals?
4.Write the symmetry elements of normal class of Hexagonal system?
5.List the important properties and causes of calcite?
6. Name at least four clay minerals and their important engineering properties?
7.Write notes on Moh’s Scale of hardness?
8. What do you understand by ‘streak’ of minerals?
Part – B
1) A) Describe physical properties of Feldspars family?
B) Write a note on properties, behaviors and engineering significance of clay minerals?
2) Write short notes on following rocks of the engineering properties occurrences and distribution .
1) Granite
2) Basalt
3) Sandstone
4) Marble
3) A) Describe the physical properties and engineering properties of Quartz and Feldspar group of minerals?
B) Write the physical properties of Hornblende, garnet, Biotite mica and augite. Discuss its role in rock strength Analysis?

4) With Examples from the mineral Kingdom, give a detailed description of the physical properties of the various minerals with example?
5) Give a detailed account of the types, properties, behavior and Engineering significant of clay minerals?
6) Write note on 1) Classification of coal and its occurrence in India
2) Petroleum and its occurrence in India
7) Write Short note on
a) Moh’s Scale of Hardness
b) Symmetry Elements of crystal
c) Physical properties of Quartz and hornblende
d) Coal occurrence in India