Engineering Geology for civil engineering.ppt

Engineering Geology for civil engineering

1. Matter and Minerals

2. Minerals: Building blocks of
rocks
•Naturally occurring
•Solid
•Inorganic
•Definite chemical
composition
•Crystal structure due
to internal
arrangement of atoms
http://www.minerals.net/gemstone/index.htm

3. General Facts about Minerals
•Between 2 - 3,000 have been identified
•A few are “native elements” -- made of only
one element, such as sulfur, gold. copper, and
graphite (carbon)
•Most are compounds, especially the silicate
group (Si, O).
•Other important groups are oxides, carbonates,
and sulfides.

4. Less than a dozen are common in
most rocks
•Quartz
•Feldspar (group)
•Muscovite (white
mica)
•Biotite (black mica)
•Calcite
•Pyroxene
•Olivine
•Amphibole (group)
•Magnetite, limonite,
and other iron oxides
•Pyrite

5. How do we identify minerals?
•Physical properties:
Color
Luster
Hardness
Crystal shape
Cleavage
Specific gravity
Other

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

7. A mineral can be many different
colors. Below is Mica.

8. Many minerals can be the same color.
Below are gold colored minerals. Which
one is gold?

9. Physical Properties of Minerals
•Color:
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

10. Gold
•When gold is run
across a streak
plate it makes a
yellowish-gold
color.

11. Pyrite or “Fool’s Gold”
•When pyrite is run
across a streak plate,
it has a black or dark
green streak.
•Pyrite is not worth
much money, while
gold is worth a lot.
They look alike, so
miners call it fool’s
gold.

12. Hematite
•Hematite’s color is
grey, but its streak
is red.
•Hema means blood.
•The mineral was
named hematite
because it looked
like it was bleeding
when it was taken
across a streak
plate.

13. 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

14. Pyrite has metallic luster

15. Quartz has vitreous luster

16. Physical Properties of Minerals
•Hardness:
–How easy it is to scratch a mineral
–Mohs Scale of Hardness
•relative scale
•consists of 10 minerals, ranked 1 (softest)
to 10 (hardest)

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

18. Gypsum is soft, it can be scratched by
a fingernail.

19. Calcite is soft, but a little harder
because it cannot be scratched by a
fingernail, but it can be scratched by a
coin

20. Fluorite is harder. It can be scratched
by a nail, but not a coin or fingernail.

21. Diamond is the hardest mineral, so
it scratches every mineral.

22. Physical Properties of Minerals
•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
Quartz Pyrite

23. Physical Properties of Minerals
•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.

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

25. Physical Properties of Minerals
•Cleavage (1 direction):
Example: mica

26. Physical Properties of Minerals
•Cleavage (2 directions):
orthoclase
amphibole

27. Physical Properties of Minerals
•Cleavage (3 directions):
halite
calcite

28. Physical Properties of Minerals
•Cleavage (4 directions):
fluorite

29. Physical Properties of Minerals
•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

30. Physical Properties of Minerals
•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

31. Mineral properties
•PHYSICAL CHARACTERISTICS:
Specific Gravity S.G. is an easily measured physical property that can be readily estimated. In general,
sulphides and oxides have much higher specific gravities than silicates.
MINERAL GROUP MINERAL SPECIFIC GRAVITY
Framework Silicate Quartz 2.6-2.7
Framework Silicate Feldspar 2.6-2.7
Sheet Silicate Mica 2.8-3.0
Chain Silicate Amphibole 2.9-3.2
Chain Silicate Pyroxene 3.2-3.6
Isolated Silicate Olivine 3.3-4.4
Isolated Silicate Garnet 3.5-4.4
Sulphide Sphalerite 4.0
Sulphide Chalcopyrite 4.2
Sulphide Pyrite 5.0
Oxide Magnetite 5.2
Oxide Hematite 5.3
Sulphide Galena 7.2
Oxide Pitchblende 9.5
Element Native Gold 12.4

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

33. •Rock-forming minerals
–~30 common minerals make up most rocks in
Earth’s crust
–Composed mainly of the 8 elements that
make up over 98% of the crust
Mineral Groups

34. Mineral Groups
All others: 1.5%
Element Abundances
SilicaSilica
(SiO(SiO
44))
4-4-SILICATES
Common cations that
bond with silica anions

35. mineral formula cleavage Silicate structure
Olivine (MgFe)
2SiO
4
none Single
tetrahedron
Pyroxene (Mg, Fe) SiO
3
two cleavage
planes at 90
0
chains
Amphiboles:
Eg. hornblende
(Ca
2Mg
5)Si
8O
22(OH)
2
Two planes at
60
0
and 120
0
Double chains
Mica Muscovit
e
KAl
3Si
3O
10(OH)
2
One plane sheets
Biotite K(MgFe)
3Si
3O
10(OH)
2
Feldspars:K-feldspar
Orthoclase,
microcline
KAlSi
3O
8
Two planes at 90
0
Three dimensional
networks
Plagioclase(Ca,Na)AlSi
3
O
8
Quartz SiO
2
none Three dimensional
network
Common Silicate mineral groups

36. group member formula uses
Oxides
Sulphides
Sulfates
Native elements
Halides
Carbonates
Magnetite
Haematite
Corundum
Galena
Sphalerite
Pyrite
Gypsum
Anhydrite
Gold
Silver
Copper
Sulfur
Graphite
Halite
Flourite
Calcite
Fe
3O
4
Fe
2O
3
Al
2
O
3
PbS
ZnS
FeS
2
CaSO4.H2O
CaSO4
Au
Ag
Cu
S
C
NaCl
CaF
2
CaCO3
Ore of iron
Ore of iron
Abrasive
Ore of lead
Ore of zinc
Fool’s gold
Used for plaster
Precious metal
Precious metal
Used for Wires
Used in chemicals
pencils
Common salt
Used in chemicals
Used in cement
Common Non Silicate mineral groups

37. –Oxides O
2-
–Carbonates (CO
3)
2-
–Sulfides S
2-
–Sulfates (SO
4)
2-
–Halides Cl
-
, F
-
, Br
-
–Native elements(single elements; e.g., Au)
Mineral Groups
•Silicates (most abundant)
•Non-silicates (~8% of Earth’s crust):

38. Mineral Groups – Silicates
•Silicates
–Tetrahedron
•fundamental
building block
•4 oxygen ions
surrounding a
much smaller
silicon ion
Silicon-oxygen
tetrahedron
(SiO
4)
4-

39. Mineral Groups – Silicates
•Joining Silicate Structures
–How tetrahedra may be linked:
•independent tetrahedra
•single chains
•double chains
•sheets
•3-D framework

40. Mineral Groups
– Silicates –

41. Olivine Group
dark silicates (Fe-Mg)
Mineral Groups – Silicates
No cleavage
 ferromagnesian

42. The Olivine group is composed of three minerals, with the
following formulas:
Forsterite = Mg
2
SiO
4
Olivine (Chrysolite) = (Mg,Fe)
2
SiO
4
Fayalite = Fe
2SiO
4
The intermediate variety, Olivine, is not scientifically
recognized as a separate mineral, but is nevertheless
mentioned.
Magnesium iron silicate. The series ranges from
the magnesium end member, Forsterite, through
the intermediate member, Olivine (also known as
Chrysolite), to the iron end member, Fayalite
Composition

43. Color Olive-green, yellow-green, light
green, yellow, yellow-brown,
brown, gray, white
Streak Colorless
Hardness 6½ - 7
Crystal Forms
and Aggregates
Usually occurs as rounded
grains, in dense aggregates of
grainy crystals, and as fractured
masses.
Transparency Transparent to translucent
Specific Gravity 3.2 - 4.2
Luster Vitreous
Cleavage none
Fracture Conchoidal
Tenacity Brittle

44. Uses The variety Peridote is a famous
gem. It creates a distinctive,
yellow-green to olive-green gem
that is well known. It is the
birthstone for August.
Olivine is also used as a flux for
making steel, and is an ore of
magnesium.
Striking Features Color, localities, and hardness
Complex Tests Soluble in hydrochloric acid

45. Pyroxene Group
Ferromagnesian / dark silicates (Fe-Mg)
Mineral Groups – Silicates
2-directions
of cleavage
(at nearly 90 degrees)
Augite

46. Minerals
The typical pyroxene structure
contains chains of SiO
3

tetrahedrons
•The slope of the tetrahedral
pyramids helps to determine
the cleavage angle of the
pyroxenes at nearly 90
o

degrees (actually 93
o
and
87
o
).

47. Pyroxene minerals are common in in meteorites and the
extrusive igneous rock called basalt. There are many
different types of pyroxene including augite, wollastonite,
diopside, enstatite, and hypersthene. All of the types contain
Si
2
O
6
but some have sodium (Na) while others have iron
(Fe), magnesium (Mg), or a combination of these three
elements . The general properties of the more common
pyroxene minerals, such as augite, are listed below.
Shape:Orthrorhombic or Monoclinic
Luster: Glassy or metallic
Color: Black
Streak: White, light green or light brown
Hardness: 5-6.5 on Mohs hardness scale
Cleavage: Two planes that meet at nearly a 90-degree angle
Fracture: Most have uneven and brittle fractures.

48. Amphibole Group
Ferromagnesian / dark silicates (Ca, Fe-Mg)
Mineral Groups – Silicates
2-directions
of cleavage
(not at 90 degrees)
Hornblende

49. There are several different minerals within the amphibole
group, but the most common type is hornblende. You can
find small crystals of hornblende in many types of igneous
rocks. They often look like little dark specks.
Hornblende (Ca
2
Mg
5
)Si
3
O
22
(OH)
2
Shape: Monoclinic (crystals look like short, six-sided
columns)
Luster: Glassy or milky
Color: Black or dark green, translucent to opaque
Streak: Grey-green or grey-brown
Hardness: 5-6
Cleavage: Two planes that meet at a 124-degree angle
Fracture: Uneven brittle fracture

50. Mica Group and Clay Minerals
light silicates (K, Al)
Mineral Groups – Silicates
1-direction
of cleavage
Muscovite
 non-ferromagnesian

51. Minerals
•Micas and Clay Minerals
•Sheets of tetrahedra are the
building blocks. Aluminum
is also involved in thesesheet
structures which are charge-
balanced by the cations Mg,
Na and K.
•most common mica
minerals:muscovite , biotite

52. Mica minerals make some rocks sparkle! They are often found in
igneous rocks such as granite and metamorphic rocks such as schist.
They sparkle because light is reflected on their flat surfaces, which are
where the mineral breaks along its plane of cleavage. These minerals
break so easily along their cleavage that some crystals have broken into
many thin layers that look like the pages of a little book.

53. Biotite
K(MgFe)
3
Si
3
O
10
(OH)
2
•Shape: Monoclinic.
Forms flat plates.
•Luster: Pearly, metallic
•Color: Dark brown, dark
green or black
•Streak: White
•Hardness: 2.5-3
•Cleavage: Yes,
•one plane of cleavage
•Fracture: The mineral is
rather flexible and so it
doesn’t fracture very
easily. In fact you can
bend it very far before it
breaks.
Muscovite
KAl
3
Si
3
O
10
(OH)
2
•Shape: Monoclinic. Forms flat
plates.
•Luster: Pearly, metallic
•Color: Colorless or lightly
tinted
•Streak: White
•Hardness: 2-3 on Mohs
Hardness Scale
•Cleavage: Yes, one plane of
cleavage
•Fracture: This mineral is also
flexible and doesn’t fracture
very easily.

54. Feldspar Group
light silicates (K-Na-Ca, Al)
Mineral Groups – Silicates
2-directions
of cleavage
(at 90 degrees)
Orthoclase
Plagioclase
K-feldspar
Ca/Na-feldspar
Most common mineral group

55. Minerals
•Feldspar group
•A second group of alumino-
silicates, tetrahedra form
three-dimensional
frameworks with Ca, Na and
K as the balancing cations.
•The very abundant
•feldspar are K-Na bearing
alkali
The K-feldspars or alkali felspars:
•Microcline, (Potassium aluminum
silicate)
•Orthoclase, (Potassium aluminum
silicate)

56. Feldspar is the most common mineral in the Earth’s crust, so you
are very likely to find it in the rocks you collect! It is found it all
of the three rock types, but is most common in intrusive igneous
rocks like granite where the crystals look white or pink.
There are several types of feldspar. The characteristics of the two
most common types are listed below. These two common types of
feldspar are difficult to tell apart besides their color. Color can be
helpful, but beware because the same mineral can often have
different colors. The sure way to tell these two apart is by looking
at the crystal surfaces for thin parallel groves called striations.
Plagioclase feldspar has striations but orthoclase feldspar does
not.

57. Orthoclase K AlSi
3O
8
•Shape: Monoclinic (Flat tabular or prism-shaped crystals)
•Luster: Glassy or pearly
•Color: Cream to pink
•Streak: White
•Hardness: 6 on Mohs Hardness Scale
•Cleavage: perfect
•Fracture: brittle
Plagioclase CaNaAlSi
3O
8
•Shape: Triclinic (Single prism-shaped crystals are very rare. You
are much more likely to find many crystals that have grown together
in a mass.
•Luster: Glassy or pearly
•Color: White to gray
•Streak: White
•Hardness: 6-6.5
•Cleavage: perfect
•Fracture: brittle

58. Quartz
light silicates (pure SiO
2)
Mineral Groups – Silicates
no cleavage
(conchoidal fracture)
hard, resistant to weathering
Quartz

59. Quartz is one of the most common mineral in Earth’s crust!
Silica (Si) and Oxygen (O) are the only elements within pure quartz.
Quartz can be found in all sorts of rocks. Most sand is made of quartz
because it is hard and does not weather away easily. Some pieces of
quartz are white like milk but most are clear like glass, sometimes with a
little pink or grey tinge of color.
Quartz
Shape: Trigonal (Perfect crystals are usually 6-sided prisms with a
pyramid shape at the end. However, it is much more common to find
many crystals that have grown in a mass or broken crystals.)
Luster: vitreous
Color: Colorless or white. Some varieties are pink or smoky.
Streak: White
Hardness: 7
Cleavage: None
Fracture: Conchoidal

60. Minerals
•Quartz
•Silica tetrahedra alone can
form a neutral three-
dimensional framework
structure with no need for
other cations.
This arrangement forms a very
stable structure
popular as ornamental stone and as gemstones
•Amethyst is the purple gemstone variety.
•Citrine is a yellow to orange gemstone variety that is rare in nature but is often created by heating
Amethyst.
•Milky Quartz is the cloudy white variety.
•Rock crystal is the clear variety that is also used as a gemstone.
•Rosey Quartz is a pink to reddish pink variety.
•Smoky quartz is the brown to gray variety.

62. Mineral Groups
Ferromagnesian
Silicates (Fe, Mg)
Non-ferromagnesian
Silicates (K, Na, Ca, Al)
Oxides
Carbonates
Sulfides/sulfates
Native elements

63. 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:
–Carbonates
–Evaporites
–Oxides
–Sulphides
– Phosphates

64. Non silicates:
•Carbonates Co3
•The important carbonates are the minerals calcite and dolomite. Both are significant
rock-forming minerals.
•The calcite group
•Calcite (Calcium Carbonate)
•Magnesite(Magnesium Carbonate)
•Rhodochrosite (Manganese Carbonate)
•Siderite(Iron Carbonate)
•Smithsonite (Zinc Carbonate)
Minerals

65. Minerals
Non silicates:
•Evaporites:
including the minerals halite, and fluorite;
Sulphates including the minerals gypsum and anhydrite.
The most famous halide mineral, halite (NaCl) or rock salt

66. Minerals
Non silicates:
•Evaporites
•Fluorite: CaF2, Calcium Fluoride

67. Minerals
Non silicates:
•Gypsum:CaSO4-2(H2O), Hydrated Calcium Sulfate

68. Minerals
Non silicates:
•Oxides
•oxides (hematite and magnetite)
Fe2O3, Iron Oxide
•hydroxides (limonite and goethite)
•important minor constituents in rocks.
•aluminum oxide bauxite can also occur as a rock-forming mineral.
•oxide minerals are exploited as economic sources of many elements including aluminum,
antimony, iron, manganese, tin, and uranium.

69. Minerals
Non silicates:
•Sulphides
•The mineral pyrite is the only sulphide that occurs commonly in rocks.
•Sulphides are most important as economic minerals providing the main sources of
elements such as arsenic, copper, lead, nickel, mercury, molybdenum and zinc.
•FeS2, Iron Sulfide

70. Minerals
Non silicates:
•Sulphides
•The mineral pyrite (FeS2) is the only sulphide that occurs commonly in rocks.
•Sulphides are most important as economic minerals providing the main sources of
elements such as arsenic, copper, lead, nickel, mercury, molybdenum and zinc.
•Galena, Chalcopyrite

71. Minerals
Non silicates:
•Phosphates are relatively rare. The only important phosphate mineral is apatite.
•Ca2Fe(PO4)2 - 4H2O, Hydrated Calcium Iron Phosphate

72. Common minerals
•the most common minerals you'll find in rocks (rock
forming minerals)
•This pile contains plagioclase feldspar, potassium feldspar, quartz
, muscovite mica, biotite mica, amphibole, olivine, and calcite.

73. 2.www.earth2class.org/er/students/
Minerals.ppt
1.www.specialconnections.k
u.edu/.../cs/.../
caseb_rocks_minerals.ppt
–
3.www.lwr.kth.se/
Grundutbildning/
AE2401/.../review
%20minerals.ppt
4.www.sci.uidaho.edu/
geol111/Geology%20101/
minerals_II_jh
Acknowledged sources