SAC101 (Lecture 5 Minerals) ppt. powerpoint

SAC101 (Lecture 5 Minerals) ppt

1. Lecture-5 Lecture-5
Minerals -Minerals - Definition, Formation, Definition, Formation,
occurrence, Classification of importantoccurrence, Classification of important
Soil forming Primary minerals Soil forming Primary minerals
Silicate and Non-silicate minerals Silicate and Non-silicate minerals
Ferro and Non - ferro magnesium minerals Ferro and Non - ferro magnesium minerals

2. Elements and Compounds in Elements and Compounds in
their solid form make up…their solid form make up…

3. What is a Mineral?What is a Mineral?

4. A A MineralMineral is a naturally occurring is a naturally occurring
Inorganic SolidInorganic Solid with a definite with a definite
chemical composition and achemical composition and a
crystalline structure.crystalline structure.

5. It means that…It means that…
•It can’t be organic in
origin
•It can’t be a liquid
and..
•It has to have a crystal
structure

6. Lets put that in a list Lets put that in a list
format.format.
1. Minerals are a naturally occurring
substance
2. Minerals are solids
3. Minerals have a
definite chemical
composition

7. 4. The atoms that make up minerals
are arranged in an orderly pattern
(They form crystals)
5. Minerals are inorganic in nature

8. Minerals-DefinitionMinerals-Definition
Minerals are naturally occurring solids with a Minerals are naturally occurring solids with a
definite chemical composition and crystal definite chemical composition and crystal
structurestructure

““Solid substances composed of atoms Solid substances composed of atoms
having an orderly and regular having an orderly and regular
arrangement”arrangement”

9. General Facts about MineralsGeneral Facts about Minerals

>2000>2000 have been identifiedhave been identified

A A fewfew are “ are “native elementsnative elements” -- made of only ” -- made of only
one element, such as sulfur, gold. copper, one element, such as sulfur, gold. copper,
and graphite (carbon)and graphite (carbon)

MostMost are are compounds -compounds - especially the especially the
silicate group silicate group (Si, O)(Si, O)

Other important groups are Other important groups are oxides, oxides,
carbonates, and sulfidescarbonates, and sulfides

10. How many different minerals How many different minerals
are there on Earth???are there on Earth???
Answer:About >2000

11. ABUNDANCEABUNDANCE
More than 90% of the minerals in
the Earth’s Crust, are made up of
compounds containing Silicon and
Oxygen, the two most abundant
elements on Earth

12. How it How it forms- Formationforms- Formation

When molten When molten magma solidifiesmagma solidifies, different , different
elements present in them freely elements present in them freely arrangearrange in in
accordance with the accordance with the attractive forces attractive forces and and
geometric formgeometric form

Silica tetrahedron Silica tetrahedron is the is the fundamental building fundamental building
blocksblocks for the formation of different minerals for the formation of different minerals
(SiO(SiO
44) )

13. How do Minerals Form???How do Minerals Form???
1. Minerals form in cooling magma chambers

14. Different types of minerals crystallize at different Different types of minerals crystallize at different
temperaturestemperatures
Decreasing temperature
Mineral formation in a Magma Chamber
Bowen’s Reaction Series

15. High Silica High Silica content forms content forms
light-coloredlight-colored rocks. rocks.

16. While While lowerlower (but only by about 25%) Silica (but only by about 25%) Silica
content forms content forms darker-coloreddarker-colored rocks rocks

17. QuantityMode of
origin
Specific
gravity
Chemical
composition
Essential
minerals
Primary
minerals
Light
minerals
Native
elements
Accessory
minerals
Secondary
minerals
Heavy
minerals
Oxides & OH,
SO4,CO3,
Halides &
Silicates
Classification of minerals

18. Primary mineralsPrimary minerals..

Minerals that are Minerals that are original components of rocks original components of rocks
are called primary minerals. (feldspar, mica, are called primary minerals. (feldspar, mica,
etcetc.)..).

Minerals that are formed from changes Minerals that are formed from changes in in
primary minerals and rocks primary minerals and rocks are called are called secondary secondary
minerals (clay minerals). minerals (clay minerals).

19. 
Those minerals that are Those minerals that are chief constituents chief constituents of of
rocks are called as rocks are called as essential mineralsessential minerals
((Feldspars, pyroxenes, micas Feldspars, pyroxenes, micas etcetc) )

Minerals which are present in Minerals which are present in small quantitiessmall quantities, ,
whose presence or absence will not alter the whose presence or absence will not alter the
properties of rocks are called properties of rocks are called accessory accessory
minerals (tourmaline, magnetite minerals (tourmaline, magnetite etcetc))

Of the Of the >2000 >2000 known minerals, only known minerals, only fewfew occur in occur in
abundanceabundance in the Earth crust. in the Earth crust.

20. MINERALS AND THEIR MINERALS AND THEIR
CONSTITUENTSCONSTITUENTS

21. Minerals (arranged in the order of
their crystallization)
Important constituents Percent
distribution
Primary minerals
Ferro magnesium minerals
Ortho-ino silicates 16.8
Olivine Fe, Mg
Pyroxenes Ca, Na, Fe, Mg
Amphiboles Ca, Na, Fe, Mg, Al, OH
Phyllo Silicates 3.6
Biotite K, Fe, Mg, Al, OH
Muscovite K, Al, OH

22. Non-Ferro Magnesium
Tecto Silicates
Feldspars 61.0
Anorthite Ca, Al
Albite Na, Al
Orthoclase K, Al
Quartz Sio2
Secondary clay minerals
Minerals Na, K, Ca 11.6
Others Mg, Fe, Al, OH 6.0

23. Percentages of rock types at land Percentages of rock types at land
surface.surface.

Sedimentary rocks -74%Sedimentary rocks -74%

52% Shale52% Shale

15% Sandstone15% Sandstone

7% Limestone & Dolomites7% Limestone & Dolomites

Igneous rocks - 18%Igneous rocks - 18%

15% Granite15% Granite

3% Basalt3% Basalt

8% others8% others

24. Percentages of minerals at land Percentages of minerals at land
surface.surface.

30% Feldspar30% Feldspar

28% Quartz28% Quartz

18% Clay minerals and mica18% Clay minerals and mica

9% Calcite and dolomite9% Calcite and dolomite

4% Iron oxides4% Iron oxides

1% Pyroxene and amphibole1% Pyroxene and amphibole

10% others10% others

25. Different silicate minerals are Different silicate minerals are

Ortho /Neo silicates, Ortho /Neo silicates,

Ino-silicatesIno-silicates

Phyllosilicates Phyllosilicates

Tectosilicates. Tectosilicates.
There are non-silicate minerals also. These are There are non-silicate minerals also. These are
different different

oxidesoxides

Carbonates, Carbonates,

Sulphates, Sulphates,

Phosphates Phosphates etcetc

29. Main rock-forming mineral groupsMain rock-forming mineral groups
SilicatesSilicates
Non-silicates - OxidesNon-silicates - Oxides
• Building block is SiOBuilding block is SiO
44 tetrahedron tetrahedron
•
Make up the majority of crystal rocksMake up the majority of crystal rocks
•
Composed of metal + oxygenComposed of metal + oxygen
CarbonatesCarbonates
•
Important component of sedimentary rocks Important component of sedimentary rocks
• Building block is COBuilding block is CO
33 ion ion

30. SiOSiO
44
4-4-
complex ion complex ion
•
A A group of ions group of ions that is so tightly bound togetherthat is so tightly bound together
that they act like a that they act like a single unitsingle unit..
•
Building block Building block of silicate mineralsof silicate minerals
•
1 silicon ion + 4 oxygen ions1 silicon ion + 4 oxygen ions
arranged in a arranged in a triangular pyramidtriangular pyramid
•
Electrical charge of Electrical charge of -4-4

31. Plummer et al., Physical Geology 9th edition, McGraw Hill Inc, Fig 2.07

32. Silicate tetrahedron
SiO
4
4-

33. SILICATE MINERALSSILICATE MINERALS
Neosilicates / Island silicatesNeosilicates / Island silicates
InosilicatesInosilicates
PhyllosilicatesPhyllosilicates
TectosilicatesTectosilicates

34. ISOLATED SILICATES [Neosilicates]ISOLATED SILICATES [Neosilicates]

Silicon tetrahedra share Silicon tetrahedra share no oxygen anions no oxygen anions
with other tetrahedra, and so have an excess with other tetrahedra, and so have an excess
negative charge of 4-negative charge of 4-..

In the mineral In the mineral olivineolivine, this is balanced by the , this is balanced by the
insertion of a insertion of a pair of divalent cations pair of divalent cations in the in the
crystal structure, crystal structure, either or both of Mgeither or both of Mg
2+2+
and and
FeFe
2+2+
. .

The chemical formula for The chemical formula for olivineolivine is written is written
((Mg,Fe)Mg,Fe)
22SiOSiO
44, , which tells us that for every which tells us that for every
siliconsilicon, there are , there are four oxygen four oxygen and and two cationstwo cations, ,
either or both of either or both of Mg and FeMg and Fe. .

35. Neosilicates (island silicates)
SiO
4
4-
tetrahedron forms ionic bonds with cations
such as Mg
2+
, Fe
2+
Mg
2+
or Fe
2+
Example: Olivine

36. Olivine: Neosilicate structure (island silicate)
View from the side (“wall” of structure)
Plummer et al., Physical Geology 9th edition, McGraw Hill Inc, Fig 2.10
Why Mg OR Fe?
•
Same size
•
Same electrical
charge
Peridot

37. Corner Sharing Base to Base
O
2-
Si
4+
side view
3-D Side View
© S. Brachfeld 2003

38. SINGLE CHAIN SILICATES [Inosilicates]SINGLE CHAIN SILICATES [Inosilicates]
Each silicon Each silicon tetrahedron shares tetrahedron shares two oxygen anionstwo oxygen anions, one , one
with with neighbouring tetrahedronneighbouring tetrahedron, and , and one with anotherone with another, to , to
produce produce long, strongly bonded chainslong, strongly bonded chains. .
For each silicon tetrahedron, shared oxygen accounts for For each silicon tetrahedron, shared oxygen accounts for
only 1only 1- rather than the - rather than the usual 2usual 2-, so that, the excess -, so that, the excess
negative charge is now negative charge is now 2-2-, which still requires , which still requires insertion of insertion of
cationscations in the crystal structure in the crystal structure
These cations are bonded to, and serve to link, the chains, These cations are bonded to, and serve to link, the chains,
but these bonds are but these bonds are weaker than weaker than those those within the chainswithin the chains..

39. Inosilicates: Single Chains (Pyroxene)
SiO
3


Chain forms ionic bonds with cations above the tip
and below the base Contd
Boxed region when view from
How many Si
How many O
2 Si
6 O
Yellow tetrahedron in front
Blue behind and to the side
Cation, forming ionic
bond with tetrahedron
chain
Plummer et al., Physical Geology 9th edition, McGraw Hill Inc, Fig 2.11

40. Assembling a Single Chain Silicate (Pyroxene)
Build xl in this direction
© S. Brachfeld 2003

41. DOUBLE CHAIN SILICATES [Inosilicates]DOUBLE CHAIN SILICATES [Inosilicates]
As with single chain silicates, chains are As with single chain silicates, chains are
constructed by constructed by sharing of two oxygen sharing of two oxygen for each for each
silicon tetrahedronsilicon tetrahedron. .
The double chains are constructed by having The double chains are constructed by having
every second silicon along the chain share a every second silicon along the chain share a
third oxygen with a silicon from the facing chain. third oxygen with a silicon from the facing chain.
The net result is that on average, The net result is that on average, each silicon each silicon
shares 2 ½ oxygenshares 2 ½ oxygen, so the , so the excess negative excess negative
charge per silicon is reduced to 1 ½.charge per silicon is reduced to 1 ½.

42. Double Chain Silicates (Amphibole)
PAIR of SiO
4 chains that link by corner sharing in 2
directions
go

43. Plummer et al., Physical Geology 9th edition, McGraw Hill Inc, Fig 2.11
Amphibole formula is long: lots of space for
small and medium cations
Cations include Na
+
, K
+
, Ca
2+
, Mn
2+
,
Fe
2+
, Mg
2+
, Fe
3+
, Al
3+
, Ti
4+

Additional

44. SHEET SILICATES [Phyllosilicates]SHEET SILICATES [Phyllosilicates]

In this group, In this group, each silicon tetrahedron each silicon tetrahedron
shares shares three oxygen anions three oxygen anions with with
neighbouring tetrahedra, so that the neighbouring tetrahedra, so that the net net
negative charge per silicon is now 1-. negative charge per silicon is now 1-.

This produces a kind of This produces a kind of hexagonal hexagonal
honeycomb sheet,honeycomb sheet, in which all in which all tetrahedra tetrahedra
point in the same direction. point in the same direction.

This enables these layers to This enables these layers to bond with layers bond with layers
of cations at the centresof cations at the centres

45. Details
Single
chain
Double
chain
Sheet
Silicates
No. of Oxygen
shared
2 2.5 3
Net negative
charge
2 1.5 1

46. Linkages of silica tetrahedral and Alumina
octahedral sheets by mutually shared oxygen
atoms form the basis for the structure of this
group

Some of the minerals, e.g., biotite and
muscovite, are relatively susceptible to
weathering, whereas others, like clay minerals,
are resistant weathering products and further
breakdown of clays is difficult.

47. Sheet Silicates- Mica Group (Muscovite, Biotite) and Clay minerals
Every tetrahedron shares all of its basal corners.
Sharing in ONE PLANE ONLY. Tips are NOT shared.
Plummer et al., Physical Geology 9th edition, McGraw Hill Inc, redrawn after Figure 2.9