2. Minerals
Most precisely a substance must fulfill the following four
conditions, before it can be called a mineral.
I. It must occur naturally as an inorganic substance.
II. Its composition must be such that it can be represented by a
definite chemical formula.
III. It must have an orderely internal structure.
IV. Its physical properties must be fixed and controlled by
composition and structure.
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3. Common uses include:
•Aluminum--packaging, transport, building
•Beryllium--gemstones, fluorescent lights
•Copper--electric cables, wires, switches
•Feldspar--glass and ceramics
•Iron--buildings, automobiles, magnets
•Calcite--toothpaste, construction
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4. Identification of minerals and their
properties
•Every individual mineral has a certain set of
properties, which will be characteristic of that
mineral alone.
•By testing a mineral for all such properties, therefore
we can easily identify it.
•The various properties of the minerals are
i. Physical Properties
ii. Microscopic optical properties
iii. Chemical Properties
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5. Physical Properties of a mineral
•From all three Properties, only physical properties
can be easily determined and identified. These
physical properties determinations may be
supplemented by optical and chemical testing.
•The physical properties of mineral may be depend
upon several factors such as degree of aggregation,
degree of cohesion, senses, light, magnetism, heat,
electricity and other physical properties of sub-
stances.
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6. Physical Properties of a mineral
The various physical properties are:
External Appearance and Internal Structure
Cleavage
Fracture
Hardness
Specific gravity
Tenacity
Colour
Streak
Lustre
Transparency
Flourescence
Phosphorescence
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7. External Appearance and internal Structure
Most of the important minerals have been
found to possess certain definite geometric
shapes in the form of well defined solids
called crystals.
When a mineral is stated to be simply
crystalline, it does not necessarily mean
that it possesses a perfect external form, it
means that the internal arrangement of the
atoms of the mineral is same for all
specimens of that particular mineral.
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8. This study and recognition of the crystals systems is specialized branch
of geology, called crystallography.
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10. Every mineral species has been found to possess a
characteristic X-ray diffraction pattern, which can be used to
calculate the spacing between atoms in that particular mineral.
This will directly determine the internal structure of a mineral.
Xray pattern can be easily utilized to recognize the minerals
by comparing the pattern of the new unknown mineral with the
known patterns of different minerals.
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11. Cleavage
Crystallised minerals have tendancy to break more readily
in certain directions that in others, producing more or less a
smooth surface which reflects light.
This tendancy of a minerals to break along the planes of the
easiest fracture is called cleavage.
The planes along which the crystals breaks are called
cleavage plane.
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12. Mineral Hardness
• Hardness of a
mineral may be
defines as the
resistance to
scratching.
•Harder minerals will
scratch softer
minerals.
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15. Tenacity
• The tenacity of a mineral defines its characters like
brittleness,sectility, malleability,flexibility,elasticity.
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Types Represented by Example
1 Sectile Minerals can be cut with knife,very soft
mineral
Talc and graphite
2 Malleable When minerals is flattens into sheet with
hammering can be cut with a knife.
Silver and Gold
3 Brittle Minerals crumbles to grains and powder
with hammering.
Quartz , Flurite
4 Flexible Minerals can be easily bent Chlorite
5 elastic A flexible minerals can regain its original
position.
Muscovite and
biotite
16. Color
•results from ability to absorb
some wavelengths and reflect
others
•some minerals have
characteristics colors
•others vary due to chemical
differences or impurities
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19. Color & Streak
• Mineral exhibits a different color in crystal and in powdered form
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Mineral Color (Crystal) Streak (powdered)
Hematite Black Cherry-red
Chromites Greenish-black Greenish-brown
Pyrite Brass-yellow Black
The streak of a mineral can be readily observed by
scratching it on a streak plate, which is made up of
unglazed porcelain or roughened glass and scratch it
from its obscure part to give only small scratch and
powder.
21. Luster
Minerals can be termed: glassy, opaque, transparent, shiny,
or most commonly: metallic and non-metallic.
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Metallic Non-
metallic
22. Fluorescence
It is the property of a mineral due to which it may emit light when
exposed to radiations like X-ray. Example : Fluorspar
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Phosphorescence
It is that property of a mineral due to which it may emit
light when it is exposed to certain radiation or heating
or rubbing.
Example : Quartz , Fluorite.
23. Common Rock Forming Mineral
Mineral Percentages (%)
(i) Felspars 59.5
(ii) Pyroxenes 16.8
(iii) Quartz 12.0
(iv) Biotite 3.8
(v) Titanium 1.5
(vi) Apatite 0.6
(vii) Others 5.8
∑ = 100%
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The minerals which constitute the bulk of the rocks of
the earth’s crust are called the rock forming minerals.
