Physical prop of minerals

2. Appearance which results from the way the
light is absorbed
1. Colour
Lusture Appearance which result from the way light is
reflected
Colour in Minerals Material absorbs some colour
and rest is reflected
Generalization
• Al, Na, K, Ca, Mg, Ba => Colourless / Light
• Fe, Cr, Mn, Co, Ni, Ti, Cu => Dark
Unfortunatately..
For purposes of identification,
colour of mineral vary very greatly

3. Idiochromatic Minerals

4. Allochromatic Minerals

5. Uses of Mineral Colour
2.Habit General shape of a mineral including
irregularities due to growth

10. Uses of Mineral Habit
3.Cleavage When a mineral breaks in a smooth and
planer surface, The mineral is said to have
a cleavage
Cleavage Plains
Set of parallel suraface of weak
chemical bonding between parallel
layers of atoms in a mineral
Cleavage Direction Each different set of parallel
Cleavage plains has an
orientation related to crystalline structure called cleavage direction

11. Classification of cleavage

13. Parting A phenomenon thats look like cleavage but is due to
crystallographic imperfections like twin planes
Fracture Mineral that are equally strong in all direction
break in irregular Surface known as fracture
Types of fracure
Even, Uneven, Hackly, Splintery, Fibrous, Concioidal

15. Significance of conchoidal fracture

16. 4.Lustre Appearance which results from the
way light is reflected
Kind of lusture
Metalic, Vitreos, Resinous, Pearly, Silky, Adamantine, Earthy

18. Uses of lusture
5.Hardness It is a minals resistance to scratchinger
Hardness in Mineral
It is mainly controlled by the strength of the bonding between
atoms and partly by the composition and size of the atom

19. Mohs’ scale of hardness
In 1812 the german mineralogist proposed
a 10 point scale
• A scale of relative hardness based on fairly common mineral
• it is not a linear scale.
Prof Friedrish Mohs

20. Hardness of a mineral relates to its weakest bond.

21. Hardness varies in direction
Generalization
• Most hydrous mineral => H < 5
• Halides, Carboonates, phosphates, Sulphides => H < 5
• Most sulphides ( except pyrite ) => H < 5
• Anhydrous oxide and and silicate => H > 5.5

22. Identification of hardness in mineral
Practical Mineralogy
• Mark ≠ Scartch
• Always use fresh specimen
• Resversibility

23. 6.Specific Gravity Ratio of weight of mineral to the
weight of water of the same
volume
Factor affecting specific gravity
• The atomic weight of the constituent element
• The way atoms are packed in a crystal structure

24. Instrument for finding Specific gravity
Heavy Liquids

25. Variation in specific gravity
• Graphite (C) 2.1
• Quartz (SiO2) 2.6
• Calcite (CaCo3) 2.7
• Barytes (BaSo4) 4.5
• Pyrrite (FeS2) 5.0
• Galena (PbS) 7.6
• Silver (Ag) 10.3
•Gold (Au) 17.2

26. 7.Magnetism Mineral containing iron are generally
magnetic, but not necessarily.
Magnetism in mineral
• Highly Magnetic
• Moderately Magnetic
• Weakly Magnetic
• Non - Magnetic

27. Paleomagnetism

28. 8.Polymorphism
• Occurance of an element or compound
in more than one crystallographic
structure
• Each pollymorph has its own physical
properties and a distinct arrangement
of its atoms
• They are formed under different condition of pressure and
temperature

29. Dimorphism

30. Trimorphism
Polymorphs of Quratz
Stishovite , Coesite,
Low Quartz, High Quartz,
Low Tridymite, High Tridymite,
Low Cristobalite, High Crystobalite,
Kaetite

31. Pseudomorphism
• The existance of mineral with the
outward crystal form of another
mineral species
• The chemical composition and
structure belongs to one mineral
Species whereas crystal from
belongs to another
Classifications of pseudomorphs
1. Substitution
2. Encrustation
3. alteration

32. Substitution
Gradual substitution of particles of
a new mineral in a place of an old one.
Encrustation
Deposition of a coating of one mineral
on the crystals of another .
Alteration
Gradual chemical change which alters
the composition but retains old forms

33. Mineral properties based on Heat, Electricity, and Radioactivity
9.Heat
Specific Heat Amount of heat required to raise the
temperature of 1g of substance by 1
Thermal Conductivity Ratio of temperature difference
per unit thickness of a mineral
Thermal Diffusivity Measure of the velocity of heat flow
in a material
Thermal Inertia Measure of how quickly the surface
temperature of a Material can be
changed by a flow of heat into the
material

34. Fusibility Measure of how much heat it takes to melt a
sharp edge of a mineral to a round one.
Von Kobell Scale
1. Stibnite (525C)
2. Natrolite (965C)
3. Almandine (1050C)
4. Actinolite (1200C)
5. Orthoclage (1300C)
6. Bronzite (1400C)
Von Kobell