1) Define
mineralogy.
It is defined as naturally
occurring inorganic solid substance that is characterized with a definite
chemical composition and very often with a definite atomic structure. It is a
branch of geology, which deals with the various aspects related to minerals
such as their individual properties their mode of formation and mode of
occurrence.
2) How
are minerals are identified and what are the symmetry elements of crystal?
Their colour, streak, hardness,
cleavage, crystal form, specific gravity and lustre generally identify
minerals. The symmetry elements are:
i)
Plane of symmetry
ii)
Axis of symmetry
iii)
Centre of Symmetry
3) What are
the physical properties of minerals?
The
physical properties are:
i)
Colour
ii)
Lustre
iii)
Streak
iv)
Hardness
v)
Cleavage
vi)
Fracture
vii)
Tenacity
viii)
Structure
ix)
Specific gravity
x)
Form
xi)
Miscellaneous
4) Define
streak.
Streak is the colour of the
finely powdered mineral as obtained by scratching or rubbing the mineral over a
rough unglazed porcelain plate. The plate often named as streak plate. It is
important and diagnostic property of many coloured minerals.
5) What is mean by fracture and
types of fracture?
The appearance of the broken
surface of a mineral in a direction other than that of cleavage is generally
expressed by the term fracture. The types are:
i)
Even
ii)
Uneven
iii)
Conchoidal
iv)
Splintry
v)
Hackly
vi)
Earthy
7) Define
Planes/axis/Centre of symmetry.
Plane of
symmetry:
It divides a crystal into similar
and similarly placed halves. This plane provides crystal so that one half is
the mirror image of the other.
Axis of
symmetry:
If is a crystal one being
rotated, come to occupy the same position in space more than one in a complete
turn, the axis about which rotation taken place is called an axis of symmetry.
Centre of
symmetry:
A crystal has a centre of
symmetry when like faces; edges are arranged in pairs in corresponding
positions on opposite sides of a central point. The cube and bricks obviously
have centre of symmetry.
9) What
is mean by holohedral form?
The maximum symmetry elements of
the system. The form is having all the faces, which have same position with
regard to the crystallographic axis. The highest symmetry elements of the
system. The forms present in normal class of the system are holohedral form
since it has the maximum symmetry elements than the other classes.
10)
Define hexagonal system.
All those crystals, which can be
referred to four crystallographic axes of which three axes
are horizontal, equal interchangeable and intersecting each
other at 1200 between the positive ends. The fourth axes are
vertical and at right angles to the three horizontal axes, are grouped under
hexagonal system.
11) Give
the physical properties and uses of mica?
The mica group only muscovite and
biotite are of common occurrence as rock forming minerals.
S.no properties muscovite biotite
1 Colour Transparent, gey or light brown Brown to black
2 Streak Uncoloured Same as colour
3 Cleavage perfect perfect
4 Lustre Vitreous Vitreous
5 Hardness 2-2-5 2-2-5
6 Specific
gravity 2.8-3.1 2.6-3.1
7 System Monoclinic Monoclinic
12) What
are the chemical compositions in feldspar group?
The feldspars are chiefly
aluminosilicates of Na, K and Ca with following general formula:
WZ4O8
In which
= Na, K, Ca ad Ba and Z = Si and Al
Some
examples of chemical composition of feldspar minerals are
i) Na Al Sio3 O8 ii) K Al Sio3 O8 iii) Ca
Al2 Si2O8
13)
Mention the various types of forms?
Any group of similar faces
showing identical mathematical relations with crystallographic axes makes a
form. Forms are further distinguished into the following types:
a) Holohedral
form
b) Hemihedral
form
c) Hemimorphic
form
d) Enantiomorphic
form
e) Fundamental
form
f) Open and
closed form
14)
What are the five symmetry classes in
Isometric system?
The types are:
a) Axes
of symmetry: 13 in all
3 are axes of four-fold symmetry
4 are axes
of three-fold symmetry
6 are axes
two fold of symmetry
b) Planes of
Symmetry: 9 in all
3 planes of
symmetry are at right angles to each other and are termed the principal planes;
6 planes f
symmetry are diagonal in position and bisect the angles between the principal
planes.
15)
Define tetragonal system?
The tetragonal system includes
all those crystals, which can be referred to three crystallographic axes so
that two axes are equal, interchangeable and horizontal in positions. The third
axis is either longer or shorter than the other two and is vertical in position
and all three axes are mutually at right angles to each other.
16)
Give the three types of pyramid.
Three
types of pyramid:
i)
Pyramid of first order: eight faces; each face
cuts the two horizontal axis at equal length besides intersecting the vertical
axis.
ii)
Pyramid of second order: Eight faces; each face
cuts only one of the two horizontal axes.
iii)
Pyramid of third order: It is also called
ditetragonal pyramid is a closed form of 16 faces in which each face cuts all
the three crystallographic axes.
17)
Draw the axial diagram for orthorhombic
system?
The three crystallographic axes
are arbitrarily designated as a, b and c. The b axis is always longer of the
two horizontal axes and is also designated as micro axis. The a axis being
shorter is designated as brachy axis.
18)
Define dome and types of domes?
A dome is defined as a form whose
faces essentially meets the vertical axis and are parallel to one of the two
horizontal axes. Two types of domes:
i) Macrodome:
An open form of two faces in which each face meets the vertical axis and the
a-axis and is parallel to the macro axis.
ii) Brachycome:
An open from of two faces each face is parallel to the brachy axis and meets
the other two axes.
19) What
are the forms allowed in monoclinic system?
The forms are:
Pinacoids
a) a-
pinacoid
b) b-pinacoid
c) c-pinacoid
ii)
Domes
a) Orthodome
b) Clinodome
iii)
Prims
a) Unit
prism
b) Orthoprism
c) Clinoprism
iv)
Pyramids
a)
Unit
pyramid
b) Orthopyramid
c) Clino
pyramid
20) Write
short notes on:
i)
Twin plane
ii)
Twin axis
Twin
plane:
It is a common to both the halves
of the crystal and across which one half may appear to be the reflection of the
other. Any pale parallel to a crystal face may be a twin plane.
Twin
axis:
It is a crystallographic
direction along which a rotation of some degrees seems to have produced the
resultant twins. In other words if a backward rotation to the same extent is
possible to be given the two parts should take the form of a singe crystal.
21) What
is the common twin law in Hexagonal system?
The laws are:
Brazillian
Law:
In this law the prism of IInd order is twin plane.
Dauphine
law: In this law c-axis is the
twinning axis. Twins are generally intergrown
Japanese
law: It contact twins result on
this law in which pyramid is a twinning plane.
22)
Define peat.
It is a
essentially a partly changed vegetable matter in the first stage of
transformation to coal. The vegetable structure is easily visible and the evidence
of its being in the process of transformation is also clearly seen. Peat is
generally composed of remains of moss like plants but 23) What is mean by
cannel coal?
It is a type of bituminous coal,
which is exceptionally rich in spores, and resins of plants, which are believed
to have been deposited by wind in subsequence condition. The cannel coal is
sometimes further distinguished as bog head coal, if in its constitution the
algal remains are dominating over the spores and resins.
24)
What are the possibilities may suggest in
Inorganic theories?
The
possibilities are:
i)
Reaction of alkali metals
ii)
Reaction of iron carbide
iii)
Concentration
iv)
Decomposition
25)
Give any one factor in controlling the
accumulation?
Lithology: Certain
types of rocks are better suited as reservoirs because of their inherent qualities
of permeability and effective porosity. Rocks with effective porosity of
greater than 15 percent and permeability greater than 1000 millidarcies are
considered 'A' class reservoirs.
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