Minerals and Their Physical Properties

1. PROPERTIES OF
MINERALS AND ROCKS
Dr. P. Sarathbabu M.Sc. B.Ed. Ph.D.
Department of Geology
Acharya Nagarjuna University

2. Minerals
What is a mineral?
 Must be solid (not made of liquid or gas).
 Must be naturally occurring (not man-made).
 Must be inorganically formed.
 Must have an orderly internal arrangement of
atoms.
 Must have a definite chemical composition
written as a formula.
• Not the same thing as minerals added to foods.

3. • To understand how minerals form, we need to
understand the characteristics of elements and
atoms.
• Chemical Elements
• Elements are the basic building blocks of
minerals. There are over 100 known elements.
• Atoms
• smallest particle of matter that exhibits
all the characteristics of an element.

4. Protons and neutrons form
the nucleus of an atom
Electrons orbit the nucleus in
discrete shells or energy levels
Physical
and chemical
properties of
minerals are
closely linked
to their atomic
structures and
compositions

5. The most abundant elements in Earth's crust are:
Oxygen (46.6% by weight)
Silicon (27.7% by weight)
Element Approximate
% by weight
Aluminum 8.1
Iron 5.0
Calcium 3.6
Sodium 2.8
Potassium 2.6
Magnesium 2.1
All others 1.5

6. All others: 1.5%
Element Abundances
Silica
(SiO4)4-
SILICATES
Common cations that
bond with silica anions

7. Minerals are divided in to TWO types
1. Silicate Minerals
2. Non-Silicate Minerals

8. Silicate Minerals
• Silicates are by far the most abundant
mineral group accounting for more than
90% of the Earth's crust.
• Silicates are the major rock-forming
minerals. It follows that oxygen and
silicon are the most abundant elements
in the crust.

9. • The basic building block of the silicates is
the silica tetrahedron. Each silicon atom
is attached to four oxygen atoms by
tetrahedral bonds. This results in a 4-
charge on the Si04 group.

10. ROCK FORMING MINERAL GROUPS
a) Olivine group
b) Pyroxene group
c) Quartz group
d) Feldspar group:
e) Mica Group
f) Amphibole group
g) Garnet group

11. Oxides
Carbonates
Sulfides/sulfates
Phosphates
Native elements
Ferromagnesian
Silicates (Fe, Mg)

12. Non-Silicate Minerals
There are a few important groups of non-silicate
minerals. Only the carbonates are significant as rock-
forming minerals.
The remaining mineral groups are often ore minerals
and provide economic sources for various elements.
The important non-silicate groups are:
a) Carbonates group
b) Oxides group
c) Sulfides/Sulfates group
d) Phosphates group
e) Native elements

13. • Olivine
SILICATE MINERALS
dark silicates (Fe-Mg)  ferromagnesian

14. • Pyroxene
SILICATE MINERALS
Ferromagnesian / dark silicates (Fe-Mg)
Augite

15. Aegirine Augite Babingtonite Enstatite
Diopside
Jadeite Omphacite Spodumene

16. • Quartz
SILICATE MINERALS
light silicates (pure SiO2)

17. Rose Quartz Amethyst Milky Quartz
Chalcedony
or Cryptocrystalline Quartz Jasper Quartz in Granite

18. • Feldspar
SILICATE MINERALS
Orthoclase
K-feldspar
Plagioclase
Ca/Na-feldspar
light silicates (K-Na-Ca, Al)

19. Potassium Feldspar
(Orthoclase)
Plagioclase Feldspar
in Anorthosite
Labradorite
Plagioclase
in Anorthosite
Potassium Feldspar
(Microcline)

20. SILICATE MINERALS
Mica Group and Clay Minerals
light silicates (K, Al)  non-ferromagnesian

21. Biotite Muscovite Phlogopite
Lepidolite
Phengite (Mariposite)
Margarite

22. SILICATE MINERALS
Amphibole Group
Ferromagnesian / dark silicates (Ca, Fe-Mg)
Hornblende

23. Actinolite
Hornblende with
Zircon and Feldspar Glaucophane
Hornblende SchistHornblendeActinolite Closeup

24. • Garnet group
• (R1 R2 Si3O12) where R1 can be Fe, Mg, Mn or Ca
• R2 can be Fe, Al or Cr
SILICATE MINERALS

25. Grossular Spessartine Uvarovite
Andradite PyropeAlmandine

26. NON-SILICATE MINERALS

27. NON-SILICATE MINERALS
• Carbonate group
(Ca, mg)CO3

28. Aragonite Dolomite Malachite
Magnesite Siderite Cerussite

29. • Oxides group (Hematite and Magnetite)
Fe2O3 Fe3O4
NON_SILICATE MINERALS

30. Corundum Hematite Ruby (Corundum)
Magnetite Psilomelane Cuprite

31. • Sulphides group (Pyrite, Chalcopyrite, Galena)
FeS2 , CuFeS2 Pbs
NON_SILICATE MINERALS

32. MarcasiteMolybdenite
SphaleriteBornite
Pyrite
Cinnabar

33. • Sulfates group
NON_SILICATE MINERALS
Barite
Alunite
Selenite Gypsum
Gypsum Rose
Gypsum
Halite

34. • Phospate group (Apatite)
• Ca2Fe(PO4)2 - 4H2O
NON_SILICATE MINERALS

35. Pyromorphite
VarisciteTurquoise

36. • Native elements (Diamond, Gold, Copper, Silver,
Graphite, and Platinum)
NON_SILICATE MINERALS

37. How do we identify minerals?
• Physical properties:
 Color
 Streak
 Luster
 Hardness
 Crystal shape
 Cleavage Vs. Fracture
 Specific gravity
 Other
Properties of Minerals

38. Physical Properties of Minerals
• Color:
• Most obvious, but often misleading
• Different colors may result from impurities
Example:
Quartz

39. Physical Properties of Minerals
Streak – color of a mineral in powdered form
(used for metallic minerals)
Obtained by scratching
a mineral on a piece of
unglazed porcelain.
Example:
Hematite

40. Physical Properties of Minerals
• Luster:
• How a mineral surface reflects light
• Two major types:
• Metallic luster
• Non-metallic luster
Metallic
example:
Galena
Non-metallic
example:
Orthoclase

41. Physical Properties of Minerals
• Hardness:
• How easy it is to scratch a mineral
• Mohs Scale of Hardness
Mineral hardness is measured on a non-linear relative scale
called Mohs Scale of Hardness
• relative scale
• consists of 10 minerals, ranked 1 (softest)
to 10 (hardest)

42. Hardness:
HARDNESS MINERAL COMMON EXAMPLE
1 Talc Pencil lead 1.0-2.0
2 Gypsum Fingernail 2.5
3 Calcite Copper penny 3.5, brass
4 Fluorite Iron
5 Apatite Tooth enamel, knife blade, glass 5.5-6.0
6 Orthoclase Steel file 6.5
7 Quartz Scratches glass
8 Topaz ------
9 Corundum Saphire, ruby
10 Diamond Synthetic diamond

43. Mohs Scale of Hardness
Hardest (10) – Diamond
Softest (1) – Talc
Common objects:
- Fingernail (2.5)
- Copper penny (3.5)
- Wire nail (4.5)
- Glass (5.5)
- Streak plate (6.5)

44. • Crystal shape (or form):
• external expression of a mineral’s internal atomic
structure
• planar surfaces are called crystal faces
• angles between crystal faces are constant for any
particular mineral
QuartzQuartz Pyrite

45. Crystal System
ISOMETRIC
DIAMOND
TETRAGONAL
WULFENITE
HEXAGONAL
BERYL
TRIGONAL
QUARTZ
variety - AMETHYST
ORTHORHOMBIC
TANZANITE
MONOCLINIC
GYPSUM
TRICLINIC
MONTEBRASITE
AMORPHOUS
AMBER

46. • Cleavage vs. Fracture:
• The way a mineral breaks
– Cleavage: tendency of a mineral to break
along planes of weakness
– Minerals that do not exhibit cleavage are
said to fracture
Do not confuse cleavage planes with crystal faces!
Crystal faces are just on the surface and may not
repeat when the mineral is broken.

47. • Cleavage is described by:
• Number of planes
• Angles between adjacent planes
– These are constant for a particular mineral

48. • Cleavage (1 direction):
Example: mica

49. • Cleavage (2 directions):
orthoclase
amphibole

50. • Cleavage (3 directions):
halite
calcite

51. • Cleavage (4 directions):
fluorite

52. • Fracture:
• minerals that do not exhibit cleavage are said
to fracture
– smooth, curved
surfaces when
minerals break in a
glass-like manner:
conchoidal fracture
Quartz

53. • Specific gravity:
• weight of a mineral divided by weight of an
equal volume of water
• metallic minerals tend to have higher specific
gravity than non-metallic minerals
Galena
SG=7.5
Quartz
SG=2.67

54. – reaction with hydrochloric acid (calcite fizzes)
• Other properties:
– taste (halite tastes salty)
– feel (talc feels soapy, graphite feels greasy)
– magnetism (magnetite attracts a magnet)

55. Properties of Rocks
Rock: Aggregated solids of minerals is called rock
All rocks are made of 2 or more minerals, but minerals
are not made of rocks.
• There are many common names for rocks and the usually give you
an idea of how big the rock is. Here are a few:
• Mountain - huge, giant hunk of rock that is still attached to the
earth's crust, doesn't move, tall
• Boulder - large, taller than a person
• rock - large, you could get your arms around it or a bit smaller but it
is usually jagged,
broken off a bigger piece of rock
• River rock - round rocks that are along the edge & at the bottom of
fast-flowing rivers
• Stone - medium, you could hold it in two hands
• Pebble - small, you can hold it with two fingers, could get stuck in
your shoe, usually rounded
• Sand - made up of tiny pieces of rock, grains of sand
• Grain - tiny, like a grain of rice or smaller, often found on a beach
• Dust - really fine powder that is mixed in with sand or soil

56. There are three rock types
Igneous: born of fire. Form from crystallized
molten rock. Form inside earth or erupt onto
earth’s surface. Water freezing to form ice.
Metamorphic: change rock. Change produced by
heat, pressure, fluids. Takes time. NO
MELTING.
Sedimentary: composed of sediment. Clastic and
chemical sediment. Form at or near earth’s
surface.

57. What type of rock is formed when
magma cools and hardens?
Characteristics
A tough, frozen melt with little texture or layering;
mostly black, white and/or gray minerals; may look like
granite or like lava

58. What type of rock is formed
when change occurs from heat
and pressure in the Earth?
Characteristics
Hardened sediment with layers (strata) of sandy or
clayey stone; mostly brown to gray; may have
fossils and water or wind marks

59. What type of rock is formed when
weathering and erosion cause
sediments to press together in
layers?
Characteristics
Tough rock with layers (foliation) of light and dark
minerals, often curved; various colors; often glittery

60. The Rock Cycle
Any rock can become any other rock through
the rock cycle.

61. Igneous rocks
There are 5 main kinds of igneous rocks, depending on
the mix of minerals in the rocks.
1.Granite
Grain size : Coarse grained
Usual Colour : Light (Leucocratic)
Structure : Holocrystalline
Texture : Inequi granular – equi granular
Composition : feldspar and quartz with minor
mica, amphibole or pyroxene

63. 2. Diorite
Grain size : Coarse grained
Usual Colour : Leucocratic
Structure : Holocrystalline
Texture : Inequi granular – equi granular
Composition: low-calcium plagioclase and dark
minerals

64. 3. Gabbro
Grain size : Coarse grained
Usual Colour : Melanocratic
Structure : Holocrystalline
Texture : equigranular, hypidomorphic
Composition: contains feldspar & one or more dark
mineral. The dark minerals are dominant.

65. 4. Peridotie
Grain size : Coarse grained
Usual Colour : Melanocratic
Structure : Holocrystalline
Texture : equigranular, hypidomorphic
Composition: olivine with amphibole
and/or pyroxene

66. 5. Pegmatite
Grain size : very coarse grained, beautiful crystal outlines
Usual Colour : Leucocratic
Structure : Holo-crystalline
Texture : inequigranular
Composition : granite with large crystals of quartz,
feldspar and mica.

67. Dunite
Grain size : Medium grained
Usual Colour : green (mesocratic)
Structure: Holocrystalline
Texture: equigranular
Composition : at least 90% olivine

68. Basalt
Grain size : fine or mixed
Usual Colour : mesocratic
Composition : low-silica lava

69. Dolerite
Grain size : Coarse grained
Usual Colour : mesocratic
Structure: Dense, massive and compact rock
Texture: Holocrystalline, equigrannular
Composition : contains feldspars, hornblende (dark) is
chief mineral, ilmenite,magnatite, qtz and biotite
minerals are accessories

70. Metamorphic rocks are igneous or sedimentary rocks
that have been transformed by great heat or
pressure.
• Foliated metamorphic rocks have layers, or banding.
Slate is transformed shale. It splits into smooth
slabs.
Schist is the most common metamorphic rock.
Mica is the most common mineral.
Gneiss has a streaky look because of alternating
layers of minerals.
• Non-foliated metamorphic rocks are not layered.
Marble is transformed limestone.
Quartzite is very hard.

71. 1. Slate
Grain size : fine grained
Usual Colour : Bluish black (mlno)
Structure: fine grained
Texture: fine texture
Composition :"tink" when struck

72. Phyllite
Grain size : fine grained
Usual Colour : shows variety of colours
Structure: schistos
Texture: fine grained
Composition : quartz, chlorite, mica,
alibite, pyrite

73. 2. Mica
Grain size : fine grained
Usual Colour : shows variety of
colours
Structure: schistos
Texture: fine grained
Composition : quartz, chlorite, mica,
alibite, pyrite

74. 3. Schist
Grain size : fine grained
Usual Colour : shows variety of
colours
Structure: schistos
Texture: fine grained
Composition : quartz, chlorite,
mica, alibite, pyrite

75. 4. Gneiss
Grain size : coarse grained
Usual Colour :leucocratic
Structure: gneissos
Texture: granoblastic
Composition : feldspars mica,

76. Non-foliated metamorphic rocks
1. Marble
Grain size : coarse grained
Usual Colour : white, pink
Structure: coarse grained
Texture: granoblastic
Composition : calcite

78. Non-foliated metamorphic rocks
2. Quartzite
Grain size : coarse grained
Usual Colour : Brown
Shape: Angular
Texture: Granoblastic
Structure: coarse grained
Composition: :
Quartz,feldspars,mica and
heavy minerals

80. • There are 5 main kinds of sedimentary rocks
depending on the appearance of the rock.
• Conglomerate rock has rounded rocks (pebbles,
boulders) cemented together in a matrix.
• Sandstone is a soft stone that is made when sand
grains cement together. Sometimes the sandstone is
deposited in layers of different colored sand.
• Shale is clay that has been hardened and turned
into rock. It often breaks apart in large flat sections.
• Limestone is a rock that contains many fossils and
is made of calcium carbonate &/or microscopic
shells.
• Breccia has jagged bits of rock cemented together
in

81. Conglomerate
Grain size : coarse grained >256mm
Usual Colour : Brown
Shape: sub angular-rounded
Structure: Clastic, crude bedding
Composition : Quartz, jaspecr

82. Sandstone
Grain size : coarse
grained
Usual Colour : Brown
Shape: subangular-
subrounded
Structure: crude bedding
Composition : Quartz,
feldspar

84. Shale
Grain size : Fine grained
Usual Colour : Yellow-black
Shape: rounded
Structure: Lamination, closed
fabric
Composition : clay minerals,
silicates

85. Limestone
Grain size : fine grained
Usual Colour : grey
Shape: laminate
Structure: crude bedding
Composition : calcite

86. Breccia
Grain size : 2mm - >256mm
Usual Colour : Reddish Brown
Shape: Angular
Structure: Clastic, crude bedding
Composition : Quartz(pebbles)
siliceous matrin
chert